This document discusses genetics and animal breeding. It explains how genetics relates to livestock improvement and describes cell division, transmission of animal characteristics, and sex determination. Additive and non-additive gene effects are described, as well as selection of breeding stock using methods like tandem selection, independent culling levels, and selection indexes. Dominant and recessive genes, homozygous and heterozygous genotypes, and basic genetic crosses are explained. Sex linkage, linkage, crossover, and mutation are also summarized.
This document discusses genetics and animal breeding. It explains how genetics relates to livestock improvement and describes cell division, inheritance of traits, and genetic principles like dominance, sex determination, linkage and mutation. Additive gene effects from many genes cumulatively influence economically important quantitative traits like growth and milk production, while non-additive genes control fewer qualitative traits. Heritability estimates the proportion of variation due to genetics. Selection of superior breeding stock relies on performance records and expected progeny differences to make genetic progress over generations.
This document discusses principles of animal genetics including Mendelian genetics. It explains Mendel's principles of dominance, segregation, and independent assortment and how they can be used to predict genotypes and phenotypes of offspring through Punnett squares. It describes genetic material including DNA, genes, and chromosomes. It discusses how genetic material is transferred from parents to offspring and defines key genetic terms. It also covers non-Mendelian inheritance patterns like incomplete dominance and codominance.
This presentation by Susan Schoenian is the first from a five-part webinar series on "Breeding Better Sheep & Goats." The topic of this presentation is "Genetics 101."
Basis of selection in animal genetics and breeding Dr. Jayesh Vyas
The sources of information based on which the breeding value of the individual is estimated are called as the basis of selection or aids to selection or criteria of selection which are the basis of estimating the breeding value.
The breeding value so obtained is known as estimating breeding value(EBV)or probable breeding value(PBV).
The different selection criteria to estimates the B.V. of an individuals for single trait
This document discusses different mating systems used in animal breeding including inbreeding, outbreeding, and their various forms. Inbreeding, like intensive inbreeding and linebreeding, is used to concentrate desirable genes and make traits more predictable in offspring. Outbreeding, such as crossbreeding and outcrossing, brings in new genes to increase performance and avoid inbreeding depression. Different mating systems are used for goals like genetic superiority, hybrid vigor, maintaining breed characteristics, or upgrading commercial herds.
1) Meiosis reduces the number of chromosome sets from diploid to haploid through two cell divisions, resulting in four haploid daughter cells rather than the two produced by mitosis.
2) During meiosis I, homologous chromosome pairs separate and move to opposite poles, while sister chromatids remain attached. This reduces the chromosome number by half.
3) Meiosis II then separates the sister chromatids, resulting in four haploid daughter cells, each with half the number of chromosomes as the original diploid parent cell. This ensures genetic variation between gametes.
Variation in crop genomes and heterosis Shaojun Xie
Variation in crop genomes and heterosis
This document discusses sources of genetic variation in crop genomes including single nucleotide polymorphisms, insertions/deletions, transposons, epigenetics, and expression level differences. It explores how prevalent these types of variation are and how they behave in plant breeding. The document also discusses heterosis, or hybrid vigor, and how transgressive segregation contributes to phenotypic diversity. Molecular mechanisms underlying heterosis like dominance, overdominance, and gene expression levels in hybrids are examined. While many genes are expressed at mid-parent levels in hybrids, some are uniquely present or expressed. The potential role of improved gene interactions restoring proper developmental transitions and stress responses in hybrids is proposed.
This document discusses genetics and animal breeding. It explains how genetics relates to livestock improvement and describes cell division, inheritance of traits, and genetic principles like dominance, sex determination, linkage and mutation. Additive gene effects from many genes cumulatively influence economically important quantitative traits like growth and milk production, while non-additive genes control fewer qualitative traits. Heritability estimates the proportion of variation due to genetics. Selection of superior breeding stock relies on performance records and expected progeny differences to make genetic progress over generations.
This document discusses principles of animal genetics including Mendelian genetics. It explains Mendel's principles of dominance, segregation, and independent assortment and how they can be used to predict genotypes and phenotypes of offspring through Punnett squares. It describes genetic material including DNA, genes, and chromosomes. It discusses how genetic material is transferred from parents to offspring and defines key genetic terms. It also covers non-Mendelian inheritance patterns like incomplete dominance and codominance.
This presentation by Susan Schoenian is the first from a five-part webinar series on "Breeding Better Sheep & Goats." The topic of this presentation is "Genetics 101."
Basis of selection in animal genetics and breeding Dr. Jayesh Vyas
The sources of information based on which the breeding value of the individual is estimated are called as the basis of selection or aids to selection or criteria of selection which are the basis of estimating the breeding value.
The breeding value so obtained is known as estimating breeding value(EBV)or probable breeding value(PBV).
The different selection criteria to estimates the B.V. of an individuals for single trait
This document discusses different mating systems used in animal breeding including inbreeding, outbreeding, and their various forms. Inbreeding, like intensive inbreeding and linebreeding, is used to concentrate desirable genes and make traits more predictable in offspring. Outbreeding, such as crossbreeding and outcrossing, brings in new genes to increase performance and avoid inbreeding depression. Different mating systems are used for goals like genetic superiority, hybrid vigor, maintaining breed characteristics, or upgrading commercial herds.
1) Meiosis reduces the number of chromosome sets from diploid to haploid through two cell divisions, resulting in four haploid daughter cells rather than the two produced by mitosis.
2) During meiosis I, homologous chromosome pairs separate and move to opposite poles, while sister chromatids remain attached. This reduces the chromosome number by half.
3) Meiosis II then separates the sister chromatids, resulting in four haploid daughter cells, each with half the number of chromosomes as the original diploid parent cell. This ensures genetic variation between gametes.
Variation in crop genomes and heterosis Shaojun Xie
Variation in crop genomes and heterosis
This document discusses sources of genetic variation in crop genomes including single nucleotide polymorphisms, insertions/deletions, transposons, epigenetics, and expression level differences. It explores how prevalent these types of variation are and how they behave in plant breeding. The document also discusses heterosis, or hybrid vigor, and how transgressive segregation contributes to phenotypic diversity. Molecular mechanisms underlying heterosis like dominance, overdominance, and gene expression levels in hybrids are examined. While many genes are expressed at mid-parent levels in hybrids, some are uniquely present or expressed. The potential role of improved gene interactions restoring proper developmental transitions and stress responses in hybrids is proposed.
This document discusses inheritance, types of reproduction, genetic and environmental variation, cloning plants and animals, and genetic engineering. It explains that genes are passed from parents to offspring and control proteins. Sexual reproduction provides variation through mixing genes but is riskier, while asexual reproduction replicates the parent. Plant cloning uses cuttings or tissue culture to duplicate plants identically. Animal cloning transfers embryos or adult cells to create clones. Genetic engineering modifies organisms by inserting genes from one into another, with potential applications like treating genetic diseases or producing insulin in plants.
The document discusses different mating systems such as monogamy, polyandry, and polygamy. It addresses factors that influence which system is evolutionarily adaptive, including parental investment, operational sex ratio, reproductive rates, and benefits/risks of each system. Examples are provided for different mating behaviors in species from insects to mammals. The diversity of polygamous systems is also examined, including female defense, resource defense, scramble competition, and leks.
This document summarizes meiosis and sexual life cycles. It discusses how meiosis and fertilization produce genetic variation through independent assortment of chromosomes, crossing over, and random fertilization. This genetic variation is the raw material for evolution by natural selection and allows organisms to evolve and adapt to their environment. Sexual reproduction, through meiosis and fertilization, generates new combinations of genes not present in the parents, increasing genetic diversity within populations.
The document discusses the history and concepts of heterosis or hybrid vigor in plant breeding. It covers pre-Mendelian observations of hybrid vigor in the 1700s and 1800s. It then discusses the early 20th century work of scientists like Shull, East, and Jones who studied heterosis and coined related terms. The document also summarizes various theories for the genetic and physiological basis of heterosis, such as dominance, overdominance, and epistasis hypotheses. It discusses evidence from studies of embryos, seedlings, biochemistry, and gene interactions that help explain the mechanisms behind heterosis. While the full basis is still unknown, heterosis continues to be widely used in crop breeding.
Sex determination refers to the developmental programme that commits the embryo to either the male or the female pathway. The animal kingdom possesses a wealth of mechanisms via which gender is decided, all of which are represented among the insects.
1. There are two main types of mating systems - random mating and non-random mating. Random mating involves each gamete having an equal chance to unite with any other gamete. Non-random mating includes assortative mating, where similar individuals mate, and disassortative mating, where dissimilar individuals mate.
2. Sewall Wright first proposed five mating systems in 1921 - random mating, genetic assortative mating, genetic disassortative mating, phenotypic assortative mating, and phenotypic disassortative mating. These systems influence the variation, homozygosity, and other genetic characteristics of populations over generations.
3. Random mating maintains diversity but can increase homozygosity in small populations.
This document provides information about genetics and heredity. It defines key terms like DNA, genes, chromosomes, and genotypes. It explains that DNA contains the instructions for building proteins, and that genes are segments of DNA that code for proteins. Chromosomes are structures that DNA winds into. Humans have 23 chromosome pairs. The document also covers inheritance patterns, including dominant and recessive alleles, and uses examples like eye color and blood types to demonstrate genetic concepts. It distinguishes between monogenic and polygenic traits and notes that both genes and the environment contribute to a person's phenotype.
Genetic variability within a population measures the variety of genotypes that exist. It is important for biodiversity and a population's ability to adapt to environmental changes. Genetic variability is produced through three main sources: meiosis, mutations, and random mating. Meiosis involves crossing over during prophase I, which exchanges alleles between homologous chromosomes, producing new combinations. It also involves random orientation of homologous chromosomes during metaphase I and sister chromatids during metaphase II. This, along with random fertilization, results in an effectively infinite number of genetically unique gametes. Mutations, such as point mutations and insertions/deletions, introduce new variants over long periods of time and act as an evolutionary mechanism of diversity.
This powerpoint gives a clear picture on inbreeding and also about outbreeding of higher organisms. This also explains the advantages and disadvantages of the above said topics. the methods of inbreeding and reasons for inbreeding also given in this powerpoint.
Sexual reproduction involves two parents, meiosis, and results in genetically diverse offspring due to crossing over and independent assortment of chromosomes during meiosis. Asexual reproduction involves one parent, mitosis, and produces identical offspring, but allows organisms to reproduce in less favorable environments with fewer variations among offspring. Bacteria can reproduce asexually through binary fission or exchange genetic material through conjugation, a form of horizontal gene transfer.
Genetical and physiological basis of heterosis and inbreedingDev Hingra
This document discusses the genetic and physiological basis of heterosis and inbreeding depression. It defines heterosis as the superiority of F1 hybrids over their parents in traits like yield, vigor and adaptation. The document discusses two main theories for the genetic basis of heterosis - the dominance hypothesis, which states that heterosis is due to the masking of deleterious recessive alleles by dominant alleles, and the overdominance hypothesis, where the heterozygote is superior to either homozygote. Physiologically, heterosis is manifested through increased embryo weight, higher early seedling growth rates, and greater nutrient absorption in hybrids. Inbreeding depression is the opposite of heterosis and results from mating closely related individuals and the
Inbreeding coefficient
Inbreeding and self-fertilization
Genotypes mate at random with respect to their genotype at this particular locus.
There are many ways in which this assumption might be violated:
• Some genotypes may be more successful in mating than others, sexual selection.
• Genotypesthataredifferentfromoneanothermaymatemoreoftenthanexpecteddisassortative mating, e.g., self-incompatibility alleles in flowering plants, MHC lociinhumans (the smelly t-shirt experiment)
• Genotypesthataresimilartooneanothermaymatemoreoftenthanexpectedassortativemating.
• Some fraction of the offspring produced may be produced asexually.
• Individuals may mate with relatives inbreeding.
– self-fertilization
– sib-mating
– first-cousin mating
– parent-offspring mating
– etc.
Evolutionary equilibrium, also known as Hardy Weinberg equilibrium, occurs when allele and genotype frequencies remain constant between generations in a population with no evolutionary forces. There are five main destabilizing forces that disrupt evolutionary equilibrium: 1) genetic drift, such as bottleneck and founder effects, which cause changes in allele frequencies by chance, 2) mutation, which introduces new alleles, 3) migration or gene flow between populations, which prevents divergence, 4) meiotic drive, where some alleles are overrepresented in gametes, and 5) natural selection, where some alleles provide a reproductive advantage. Together, these evolutionary forces ensure that Hardy Weinberg equilibrium is rarely achieved in natural populations.
Heterosis, also known as hybrid vigor, refers to the increased or superior characteristics of offspring compared to their parents. This document discusses the history and genetic models of heterosis. It was first described by Charles Darwin and later termed "heterosis" by Shull. Genetic models like dominance, overdominance, and epistasis aim to explain the superior performance of hybrids. While early models focused on alleles, more recent research explores the role of epigenetic factors like DNA methylation and how interaction between genetic and epigenetic variations contribute to heterosis. The molecular basis remains complex and varies depending on organism, population, and trait.
Genetic variation is produced within populations through mutations, sexual reproduction, and meiosis. Mutations introduce new alleles and variation when genes change through single-base mutations or chromosomal rearrangements. Sexual reproduction and meiosis increase variation by recombining alleles through crossing over during prophase I to form new combinations not seen in either parent. This genetic variation provides the raw material for natural selection to act upon.
Heredity refers to the passing of traits from parents to offspring. Variation means individuals have slight differences even if they belong to the same species. Genetics is the science of heredity and variation. During reproduction and cell division, small inaccuracies in DNA copying can lead to minor variations between individuals. However, not all variations provide equal chances of adaptation, as some variations may provide individuals with advantages depending on the environment. Mendel's experiments with pea plants showed that traits can be dominant or recessive, and are inherited independently. DNA contains the genetic information passed down from parents. In humans, sex is determined by X and Y chromosomes. Fossils provide evidence for evolution by showing extinct organisms and transitional forms between
This chapter discusses heredity and evolution. It covers Mendel's principles of inheritance including segregation and independent assortment. Examples of Mendelian traits in humans like cystic fibrosis and sickle cell anemia are provided. Non-Mendelian inheritance patterns and mitochondrial inheritance are also discussed. The chapter then explores modern evolutionary theory including the definition of evolution, factors that produce variation, and how natural selection acts on variation.
Effects of Inbreeding & Inbreeding depressionShizra Imtiaz
Inbreeding can lead to inbreeding depression due to the expression of deleterious recessive alleles. When related animals breed, it increases the homozygosity of their offspring's genome, making any recessive deleterious traits more likely to be expressed. This can negatively impact traits like fertility and survivability. Inbreeding depression decreases the overall performance of animals and is exemplified by genetic defects like dwarfism. To reduce inbreeding depression, artificial selection techniques can be used like outcrossing to introduce new alleles from unrelated populations.
This document discusses polygenic or quantitative inheritance, where multiple genes each have a small effect on a trait, resulting in continuous variation in phenotypes. Key points:
- Traits like height, weight, eye color are polygenic, with no clear boundaries between types.
- The multiple factor hypothesis proposes that multiple genes, each with small effects, combine to produce quantitative variation in traits.
- Characteristics of polygenic traits include each gene having an additive, cumulative effect and no dominance or epistasis between genes. Environmental factors also influence phenotypic expression. Examples of polygenic traits in humans are skin and eye color.
This document discusses types of variation in plants, including their origin and scale. It covers genetic and environmental variation, as well as qualitative and quantitative traits. Genetic variation arises from processes like recombination, chromosome modifications, and mutations. Qualitative traits are discrete while quantitative traits exhibit continuous variation controlled by multiple genes. The document provides examples and explanations of these concepts.
1. The document discusses genetics, inheritance, and Mendel's experiments with pea plants. It defines key genetic terms and concepts.
2. Mendel conducted experiments breeding pea plants with distinct traits like plant height. His findings established basic principles of inheritance including dominance, segregation of alleles, and independent assortment.
3. Mendel determined that traits are passed from parents to offspring through discrete units (now known as genes and alleles) which segregate and sort independently during reproduction.
This passage summarizes key concepts from Gregor Mendel's experiments with pea plants including:
1) Mendel demonstrated the principles of dominance, segregation, and independent assortment by conducting a series of crosses between pea plants with different traits.
2) His work showed that genes for different traits segregate independently during the formation of gametes, resulting in genetic variations not seen in the parents.
3) While Mendel's principles apply broadly, genetics is more complex with some traits controlled by multiple genes or alleles demonstrating incomplete dominance or codominance.
This document discusses inheritance, types of reproduction, genetic and environmental variation, cloning plants and animals, and genetic engineering. It explains that genes are passed from parents to offspring and control proteins. Sexual reproduction provides variation through mixing genes but is riskier, while asexual reproduction replicates the parent. Plant cloning uses cuttings or tissue culture to duplicate plants identically. Animal cloning transfers embryos or adult cells to create clones. Genetic engineering modifies organisms by inserting genes from one into another, with potential applications like treating genetic diseases or producing insulin in plants.
The document discusses different mating systems such as monogamy, polyandry, and polygamy. It addresses factors that influence which system is evolutionarily adaptive, including parental investment, operational sex ratio, reproductive rates, and benefits/risks of each system. Examples are provided for different mating behaviors in species from insects to mammals. The diversity of polygamous systems is also examined, including female defense, resource defense, scramble competition, and leks.
This document summarizes meiosis and sexual life cycles. It discusses how meiosis and fertilization produce genetic variation through independent assortment of chromosomes, crossing over, and random fertilization. This genetic variation is the raw material for evolution by natural selection and allows organisms to evolve and adapt to their environment. Sexual reproduction, through meiosis and fertilization, generates new combinations of genes not present in the parents, increasing genetic diversity within populations.
The document discusses the history and concepts of heterosis or hybrid vigor in plant breeding. It covers pre-Mendelian observations of hybrid vigor in the 1700s and 1800s. It then discusses the early 20th century work of scientists like Shull, East, and Jones who studied heterosis and coined related terms. The document also summarizes various theories for the genetic and physiological basis of heterosis, such as dominance, overdominance, and epistasis hypotheses. It discusses evidence from studies of embryos, seedlings, biochemistry, and gene interactions that help explain the mechanisms behind heterosis. While the full basis is still unknown, heterosis continues to be widely used in crop breeding.
Sex determination refers to the developmental programme that commits the embryo to either the male or the female pathway. The animal kingdom possesses a wealth of mechanisms via which gender is decided, all of which are represented among the insects.
1. There are two main types of mating systems - random mating and non-random mating. Random mating involves each gamete having an equal chance to unite with any other gamete. Non-random mating includes assortative mating, where similar individuals mate, and disassortative mating, where dissimilar individuals mate.
2. Sewall Wright first proposed five mating systems in 1921 - random mating, genetic assortative mating, genetic disassortative mating, phenotypic assortative mating, and phenotypic disassortative mating. These systems influence the variation, homozygosity, and other genetic characteristics of populations over generations.
3. Random mating maintains diversity but can increase homozygosity in small populations.
This document provides information about genetics and heredity. It defines key terms like DNA, genes, chromosomes, and genotypes. It explains that DNA contains the instructions for building proteins, and that genes are segments of DNA that code for proteins. Chromosomes are structures that DNA winds into. Humans have 23 chromosome pairs. The document also covers inheritance patterns, including dominant and recessive alleles, and uses examples like eye color and blood types to demonstrate genetic concepts. It distinguishes between monogenic and polygenic traits and notes that both genes and the environment contribute to a person's phenotype.
Genetic variability within a population measures the variety of genotypes that exist. It is important for biodiversity and a population's ability to adapt to environmental changes. Genetic variability is produced through three main sources: meiosis, mutations, and random mating. Meiosis involves crossing over during prophase I, which exchanges alleles between homologous chromosomes, producing new combinations. It also involves random orientation of homologous chromosomes during metaphase I and sister chromatids during metaphase II. This, along with random fertilization, results in an effectively infinite number of genetically unique gametes. Mutations, such as point mutations and insertions/deletions, introduce new variants over long periods of time and act as an evolutionary mechanism of diversity.
This powerpoint gives a clear picture on inbreeding and also about outbreeding of higher organisms. This also explains the advantages and disadvantages of the above said topics. the methods of inbreeding and reasons for inbreeding also given in this powerpoint.
Sexual reproduction involves two parents, meiosis, and results in genetically diverse offspring due to crossing over and independent assortment of chromosomes during meiosis. Asexual reproduction involves one parent, mitosis, and produces identical offspring, but allows organisms to reproduce in less favorable environments with fewer variations among offspring. Bacteria can reproduce asexually through binary fission or exchange genetic material through conjugation, a form of horizontal gene transfer.
Genetical and physiological basis of heterosis and inbreedingDev Hingra
This document discusses the genetic and physiological basis of heterosis and inbreeding depression. It defines heterosis as the superiority of F1 hybrids over their parents in traits like yield, vigor and adaptation. The document discusses two main theories for the genetic basis of heterosis - the dominance hypothesis, which states that heterosis is due to the masking of deleterious recessive alleles by dominant alleles, and the overdominance hypothesis, where the heterozygote is superior to either homozygote. Physiologically, heterosis is manifested through increased embryo weight, higher early seedling growth rates, and greater nutrient absorption in hybrids. Inbreeding depression is the opposite of heterosis and results from mating closely related individuals and the
Inbreeding coefficient
Inbreeding and self-fertilization
Genotypes mate at random with respect to their genotype at this particular locus.
There are many ways in which this assumption might be violated:
• Some genotypes may be more successful in mating than others, sexual selection.
• Genotypesthataredifferentfromoneanothermaymatemoreoftenthanexpecteddisassortative mating, e.g., self-incompatibility alleles in flowering plants, MHC lociinhumans (the smelly t-shirt experiment)
• Genotypesthataresimilartooneanothermaymatemoreoftenthanexpectedassortativemating.
• Some fraction of the offspring produced may be produced asexually.
• Individuals may mate with relatives inbreeding.
– self-fertilization
– sib-mating
– first-cousin mating
– parent-offspring mating
– etc.
Evolutionary equilibrium, also known as Hardy Weinberg equilibrium, occurs when allele and genotype frequencies remain constant between generations in a population with no evolutionary forces. There are five main destabilizing forces that disrupt evolutionary equilibrium: 1) genetic drift, such as bottleneck and founder effects, which cause changes in allele frequencies by chance, 2) mutation, which introduces new alleles, 3) migration or gene flow between populations, which prevents divergence, 4) meiotic drive, where some alleles are overrepresented in gametes, and 5) natural selection, where some alleles provide a reproductive advantage. Together, these evolutionary forces ensure that Hardy Weinberg equilibrium is rarely achieved in natural populations.
Heterosis, also known as hybrid vigor, refers to the increased or superior characteristics of offspring compared to their parents. This document discusses the history and genetic models of heterosis. It was first described by Charles Darwin and later termed "heterosis" by Shull. Genetic models like dominance, overdominance, and epistasis aim to explain the superior performance of hybrids. While early models focused on alleles, more recent research explores the role of epigenetic factors like DNA methylation and how interaction between genetic and epigenetic variations contribute to heterosis. The molecular basis remains complex and varies depending on organism, population, and trait.
Genetic variation is produced within populations through mutations, sexual reproduction, and meiosis. Mutations introduce new alleles and variation when genes change through single-base mutations or chromosomal rearrangements. Sexual reproduction and meiosis increase variation by recombining alleles through crossing over during prophase I to form new combinations not seen in either parent. This genetic variation provides the raw material for natural selection to act upon.
Heredity refers to the passing of traits from parents to offspring. Variation means individuals have slight differences even if they belong to the same species. Genetics is the science of heredity and variation. During reproduction and cell division, small inaccuracies in DNA copying can lead to minor variations between individuals. However, not all variations provide equal chances of adaptation, as some variations may provide individuals with advantages depending on the environment. Mendel's experiments with pea plants showed that traits can be dominant or recessive, and are inherited independently. DNA contains the genetic information passed down from parents. In humans, sex is determined by X and Y chromosomes. Fossils provide evidence for evolution by showing extinct organisms and transitional forms between
This chapter discusses heredity and evolution. It covers Mendel's principles of inheritance including segregation and independent assortment. Examples of Mendelian traits in humans like cystic fibrosis and sickle cell anemia are provided. Non-Mendelian inheritance patterns and mitochondrial inheritance are also discussed. The chapter then explores modern evolutionary theory including the definition of evolution, factors that produce variation, and how natural selection acts on variation.
Effects of Inbreeding & Inbreeding depressionShizra Imtiaz
Inbreeding can lead to inbreeding depression due to the expression of deleterious recessive alleles. When related animals breed, it increases the homozygosity of their offspring's genome, making any recessive deleterious traits more likely to be expressed. This can negatively impact traits like fertility and survivability. Inbreeding depression decreases the overall performance of animals and is exemplified by genetic defects like dwarfism. To reduce inbreeding depression, artificial selection techniques can be used like outcrossing to introduce new alleles from unrelated populations.
This document discusses polygenic or quantitative inheritance, where multiple genes each have a small effect on a trait, resulting in continuous variation in phenotypes. Key points:
- Traits like height, weight, eye color are polygenic, with no clear boundaries between types.
- The multiple factor hypothesis proposes that multiple genes, each with small effects, combine to produce quantitative variation in traits.
- Characteristics of polygenic traits include each gene having an additive, cumulative effect and no dominance or epistasis between genes. Environmental factors also influence phenotypic expression. Examples of polygenic traits in humans are skin and eye color.
This document discusses types of variation in plants, including their origin and scale. It covers genetic and environmental variation, as well as qualitative and quantitative traits. Genetic variation arises from processes like recombination, chromosome modifications, and mutations. Qualitative traits are discrete while quantitative traits exhibit continuous variation controlled by multiple genes. The document provides examples and explanations of these concepts.
1. The document discusses genetics, inheritance, and Mendel's experiments with pea plants. It defines key genetic terms and concepts.
2. Mendel conducted experiments breeding pea plants with distinct traits like plant height. His findings established basic principles of inheritance including dominance, segregation of alleles, and independent assortment.
3. Mendel determined that traits are passed from parents to offspring through discrete units (now known as genes and alleles) which segregate and sort independently during reproduction.
This passage summarizes key concepts from Gregor Mendel's experiments with pea plants including:
1) Mendel demonstrated the principles of dominance, segregation, and independent assortment by conducting a series of crosses between pea plants with different traits.
2) His work showed that genes for different traits segregate independently during the formation of gametes, resulting in genetic variations not seen in the parents.
3) While Mendel's principles apply broadly, genetics is more complex with some traits controlled by multiple genes or alleles demonstrating incomplete dominance or codominance.
Genetics is the scientific study of genes and heredity of how certain qualities or traits are passed from parents to offspring (National Institute of General Medical Sciences, 2022)
1. Genetics is the study of how traits are passed from parents to offspring through chromosomes and genes. Chromosomes contain genes that determine traits and are located in cell nuclei.
2. Body cells contain pairs of chromosomes while sex cells like eggs and sperm only contain half the number to allow for chromosome pairing during fertilization.
3. Traits are passed to offspring when the chromosomes from the mother and father combine during fertilization. Dominant genes mask recessive genes, determining whether traits are expressed.
1. Genetics is the study of how traits are passed from parents to offspring through chromosomes and genes. Chromosomes contain genes that determine traits and are located in cell nuclei.
2. Body cells contain pairs of chromosomes while sex cells like eggs and sperm only contain half the number to allow for chromosome pairing during fertilization.
3. Traits are passed to offspring when the chromosomes from the sperm and egg join during fertilization. Dominant genes mask recessive genes, determining whether traits are expressed.
This document provides an overview of genetics and genetic diseases. It defines key genetic terms and describes Mendel's laws of inheritance. Genetic diseases can be caused by mutations in single genes, interactions between multiple genes and environmental factors, or chromosomal abnormalities. The mechanisms of genetic disease include alterations in DNA sequences, changes in protein function, and spontaneous chromosomal issues. Genetic disorders are classified as Mendelian, chromosomal, metabolic, somatic cell issues, or multifactorial conditions involving both genetic and external influences.
The document discusses heredity and genetics in cattle. Key points include:
- Genes located on chromosomes determine hereditary traits such as hair color and milk production. Cattle have 30 pairs of chromosomes.
- Outbreeding is highly recommended to increase heterozygous gene pairs and avoid issues from undesirable recessive genes, while inbreeding can increase homozygous gene pairs and expression of recessives.
- Traits are influenced by many gene pairs on different chromosomes. Some genes are dominant and affect simple traits.
This document provides an overview of biology concepts including:
1) Eukaryotic cells have a nucleus while prokaryotic cells do not. Both can undergo cellular respiration to produce ATP.
2) The plasma membrane controls what enters and exits the cell and is important for homeostasis. Enzymes speed up cellular reactions.
3) DNA is replicated before cell division and contains instructions for making proteins via transcription and translation.
4) Evolution occurs over time through natural selection, where organisms with favorable variations are more likely to survive and reproduce.
The document summarizes the key differences between mitosis and meiosis. Mitosis produces identical body cells through one cell division, while meiosis produces non-identical sex cells through two cell divisions. It also describes sperm cell adaptations like the acrosome for digesting the egg membrane and many mitochondria for energy production through respiration.
This document discusses different methods of fish breeding, including selective breeding, recombination breeding, and hybrid breeding. Selective breeding involves choosing individuals with desired traits to breed, and can result in reduced genetic variability over time. Recombination breeding combines traits from unrelated strains through techniques like crossbreeding and hybridization. Hybrid breeding aims to produce offspring that exhibit hybrid vigor or heterosis for increased performance. The genetic basis of heterosis includes dominance, overdominance, and epistasis effects between loci. Proper selection of parental lines and understanding of genetic processes is important for effective recombination and hybrid breeding in fish.
This document discusses Mendel's principles of inheritance and exceptions to them. It introduces the principles of dominance, segregation, and independent assortment. It then discusses exceptions like incomplete dominance, codominance, multiple alleles, polygenic traits, and epistasis. It describes how Thomas Morgan's work with fruit flies led to the principle of gene linkage, where genes on the same chromosome tend to be inherited together. Crossing over during meiosis can still separate linked genes, with closer genes being less likely to separate. Alfred Sturtevant created early gene maps by measuring recombination rates between linked genes.
Chapter 3 The New GeneticsAlma Villanueva, MACalifornia S.docxwalterl4
Chapter 3:
The New Genetics
Alma Villanueva, MA
California State University, Los Angeles
Overview
Genetic Code
The Beginning of Life
Male & Female
Twins
Genotype & Phenotype
Disorders
Genetic Counseling
Genetic Code
Cells
Basic unit of life
Trillions!
Nucleus
Chromosomes
Thread– like structures made up of DNA & protein
23 pairs
DNA (Deoxyribonucleic acid)
2 strands twisted in a double helix
Chemical composition of molecules that contain the genes
Contains all of the information required to build/maintain the cell
3
Genes
Small section of the chromosome
18,000 – 23,000 genes
Each gene provides a unique recipe to make a protein
4 bases
Code for your traits
A - adenine
T - thymine
C - cytosine
G – guanine
Only 4 possible pairs
A-T; T-A; C-G; G-C
http://mybrainnotes.com/brain-dna-behavior.html
4
Allele
A variation of a gene
Example: the gene for eye color has several variations (alleles); an allele for blue eye color or an allele for brown eyes
Everyone inherits alleles from sperm & ovum
Genetic diversity
Distinguishes each person
Allows the human species to adapt to pressures of the environment
Genome
Full set of genes with instructions to make a living organism
Genomes exist for each species
Video about Genes
5
The Beginning of Life
Two Parents, Millions of Gametes
Gamete
Reproductive cell
Sperm or Ovum
Each contains 23 pairs
Zygote
Cell formed with union of Sperm & Ovum
Produce a new individual with 23 chromosomes from each parent
Conception
http://predictingbabygender.info/tag/intercourse-timing/
Matching genes
Genotype
Organism’s entire genetic inheritance, or genetic potential.
Homozygous (same zygote)
Two genes of one pair that are exactly the same in every letter of their code
Heterozygous
Two genes of one pair that differ in some way
Usually not an issue
Male of Female?
Humans usually possess
46 chromosomes
44 autosomes and 2 sex chromosomes
SEX chromosome = 23rd pair
Female – XX
Male – XY
Mother’s contain X
Father’s may have X or Y
X chrom. Is larger & more genes
Y contain SRY,
making male hormones & organs
It's a girl!
Uncertain Sex
“ambiguous genitals,” = child's sex is not abundantly clear
a quick analysis of the chromosomes is needed, to make sure there are exactly 46 and to see whether the 23rd pair is XY or XX
shown here a baby boy (left) and girl (right).
Too Many Boys?
Is sex selection the parents’ right or a social wrong?
Preference for boys in many areas of world
Ways to prevent female birth
Inactivating X sperm before conception
In vitro fertilization (IVF)
Aborting XX fetuses
My Strength, My Daughter
slogan these girls in New Delhi are shouting at a demonstration against abortion of female fetuses in India
The current sex ratio of children in India suggests that this campaign has not convinced every couple.
New Cells
Within hours of conception
23 pairs of chromosomes carrying all the genes duplicate, forming two complete sets of the genome
Two sets.
Chapter 3 The New GeneticsAlma Villanueva, MACalifornia S.docxketurahhazelhurst
Chapter 3:
The New Genetics
Alma Villanueva, MA
California State University, Los Angeles
Overview
Genetic Code
The Beginning of Life
Male & Female
Twins
Genotype & Phenotype
Disorders
Genetic Counseling
Genetic Code
Cells
Basic unit of life
Trillions!
Nucleus
Chromosomes
Thread– like structures made up of DNA & protein
23 pairs
DNA (Deoxyribonucleic acid)
2 strands twisted in a double helix
Chemical composition of molecules that contain the genes
Contains all of the information required to build/maintain the cell
3
Genes
Small section of the chromosome
18,000 – 23,000 genes
Each gene provides a unique recipe to make a protein
4 bases
Code for your traits
A - adenine
T - thymine
C - cytosine
G – guanine
Only 4 possible pairs
A-T; T-A; C-G; G-C
http://mybrainnotes.com/brain-dna-behavior.html
4
Allele
A variation of a gene
Example: the gene for eye color has several variations (alleles); an allele for blue eye color or an allele for brown eyes
Everyone inherits alleles from sperm & ovum
Genetic diversity
Distinguishes each person
Allows the human species to adapt to pressures of the environment
Genome
Full set of genes with instructions to make a living organism
Genomes exist for each species
Video about Genes
5
The Beginning of Life
Two Parents, Millions of Gametes
Gamete
Reproductive cell
Sperm or Ovum
Each contains 23 pairs
Zygote
Cell formed with union of Sperm & Ovum
Produce a new individual with 23 chromosomes from each parent
Conception
http://predictingbabygender.info/tag/intercourse-timing/
Matching genes
Genotype
Organism’s entire genetic inheritance, or genetic potential.
Homozygous (same zygote)
Two genes of one pair that are exactly the same in every letter of their code
Heterozygous
Two genes of one pair that differ in some way
Usually not an issue
Male of Female?
Humans usually possess
46 chromosomes
44 autosomes and 2 sex chromosomes
SEX chromosome = 23rd pair
Female – XX
Male – XY
Mother’s contain X
Father’s may have X or Y
X chrom. Is larger & more genes
Y contain SRY,
making male hormones & organs
It's a girl!
Uncertain Sex
“ambiguous genitals,” = child's sex is not abundantly clear
a quick analysis of the chromosomes is needed, to make sure there are exactly 46 and to see whether the 23rd pair is XY or XX
shown here a baby boy (left) and girl (right).
Too Many Boys?
Is sex selection the parents’ right or a social wrong?
Preference for boys in many areas of world
Ways to prevent female birth
Inactivating X sperm before conception
In vitro fertilization (IVF)
Aborting XX fetuses
My Strength, My Daughter
slogan these girls in New Delhi are shouting at a demonstration against abortion of female fetuses in India
The current sex ratio of children in India suggests that this campaign has not convinced every couple.
New Cells
Within hours of conception
23 pairs of chromosomes carrying all the genes duplicate, forming two complete sets of the genome
Two sets ...
The document discusses gene concept and properties of genes. Some key points:
- A gene is the basic unit of inheritance, consisting of a sequence of DNA nucleotides that codes for a functional product like RNA or protein.
- Genes have various structural and functional properties including different forms (alleles), a fixed location on chromosomes, the ability to mutate or change form, and the ability to be expressed in different ways that influence phenotypes.
- Genes can be classified in different ways, for example based on dominance, interaction with other genes, the character they control, their effects on survival, their location, nucleotide sequence, and sex linkage.
The document summarizes key concepts about genetics and heredity, including:
- Genes contain DNA instructions that determine traits like appearance and behavior. Humans have about 25,000 genes across 46 chromosomes.
- Development begins at conception when sperm and egg fuse to form a single cell called a zygote containing a full set of genes. This cell then differentiates and multiplies to form all the body's cells and tissues.
- Genes interact with each other and the environment to determine a person's phenotype, or observable characteristics. While genes influence traits, environmental factors also play a role.
A mutation is a mistake made when DNA is copied that can be passed from parent cells to daughter cells. There are two main types of mutations: gene mutations which change a single gene, and chromosomal mutations which involve changes to whole chromosomes. Gene mutations include point mutations such as substitutions, insertions, and deletions. Chromosomal mutations include deletions, duplications, inversions, and translocations. Mutations can have harmful effects like genetic disorders but sometimes beneficial effects if they provide new functions. Prokaryotes and eukaryotes regulate genes differently, using operons, promoters/repressors, and transcription factors. Genetic disorders discussed include sickle cell anemia, cystic fibrosis, and Huntington's disease
Sexual reproduction involves the combination of genetic material from two parent organisms, while asexual reproduction involves only one parent. There are advantages and disadvantages to both methods of reproduction. Sexual reproduction results in offspring with genetic variation due to combinations of parents' genes, allowing populations to adapt, but requires finding a mate. Asexual reproduction is simpler but produces identical offspring, risking the elimination of a whole population if the environment changes.
1. Evolution occurs through natural selection acting on genetic variation in populations over multiple generations. This can result in adaptation to the local environment and possibly even speciation.
2. Darwin provided the mechanism of natural selection to explain evolution, noting that populations have high reproductive potential but limited resources, leading to competition and differential survival of heritable traits.
3. Genetic variation within populations, arising from mutations and sexual reproduction, provides variation on which natural selection acts, influencing allele frequencies over time as traits enhancing survival are selected for.
2. Objectives
Explain how genetics relates to improvement in livestock
production
Describe how cell division occurs
Diagram and explain how animal characteristics are
transmitted
Diagram and explain sex determination, linkage, crossover
and mutation
4. Additive Gene Effects
Many different genes involved in the expression of the trait
Individual genes have little effect upon the trait
Effects of each gene are cumulative with very little or no
dominance between pairs of alleles
Each member of the gene pair has equal opportunity to be
expressed
5. Traits that Result from Additive
Gene Effects
Most of the economically important traits
Carcass traits
Weight gain
Milk production
All have moderate to high heritability
Quantative
Environment often influences expression
Difficult to classify phenotypes into distinct categories because they
usually follow continuous distribution
Difficult to identify animals with superior genotypes
6. Non-Additive Gene Effect
Control traits by determining how gene pairs act in different
combinations with one another
Observable
Controlled by only one or a few pairs of genes
Typically one gene pairs will be dominant if the animal is
heterozygous for the trait being expressed.
When combinations of gene pairs give good results the
offspring will be better than either of its parents
This called hybrid vigor or heterosis
7. Traits That Result From Non-Additve
Gene Effects
Qualitative
Phenotype is easily identified
Little environmental effect
Genotype can be easily determined
8. Heritability Estimates
Heritability: the proportion of the total variation (genetic and
environmental) that is due to additive gene effects
Heritability Estimate: expression of the likelihood of a trait
being passed from the parent to the offspring
Traits that are highly heritable show rapid improvement
Traits with low heritability make take several generations of
animals for desirable characteristics to become strong
See Table 9-1,2,3 and 42-4 to see the heritability estimates
for several species of livestock
10. Selecting Breeding Stock
Computer programs and data bases developed by
Universities available
Breed associations provide information
Breeding values and Expected Progeny Difference (EPD)
help producers make fast genetic decisions
Also 3 types of systems that producers can use to select
breeding animals
Tandem
Independent Culling Levels
Selection Index
11. Tandem
Traits are selected for one at a time and selection for the
next trait does not begin until the desired level of
performance is achieved with the first.
Animals with one desirable trait but with other undesirable
ones may be kept for breeding
For the most profitable production, emphasis has to be
placed on several traits when selecting breeding stock;
Tandem selection does not do this!
Simple to use but not recommended
Least effective of the selection methods
12. Independent Culling Levels
Establishes a performance level for each trait in the selection
program. The animal must achieve that level to be kept for breeding
stock.
Selection for the breeding program is based on more than one trait
Disadvantage to this type of selection is that superior performance in
one trait cannot offset a trait that does not meet selection criteria
Most effective when selecting for only a small number of traits
Second most effective method of selection
Most widely used
13. Selection Index
Index of net merit is established that gives weight to traits based on
the economic importance, heritability and genetic correlations that
may exists between the traits
Does not discriminate against a trait with only slightly substandard
performance when it is offset by high performance in another trait
Provides more rapid improvement in overall genetic improvement in
the breeding group
Extensive records are required to establish the index
Is the most effective method of achieving improvement in genetic
merit
15. The Cell and Cell Division
Body is made up of millions of cells
Cells are the most basic and the smallest part of the body
that are capable of sustaining the processes of life
Fig 9-1
16. The Parts of Cell
Protoplasm- makes up most of the cell
Nucleus- contains the chromosomes that contain the
genes, it also controls the cells metabolism, growth and
reproduction
Cytoplasm- surrounds the nucleus and contains
mitochondria, lysosmes, Golgi apparatuses, ribosomes
Cell membrane- semipermeable, surrounds the nucleus
and cytoplasm
17. Mitosis
The division of cells in the animals body
Allows animals (and us) to grow
Replaced old cells that die
18. Chromosomes
Occur in pairs in the nucleus of all body cells except the
sperm and ovum
Each parent contributes to one-half of the pair
The number of pairs of chromosomes is called the diploid
number
The diploid number varies species to species but is
constant for each species of animal
20. So What Happens During Mitosis?
Chromosome pairs are duplicated in each daughter cell
Figure 9-2 p. 196 shows a cell going through the 4 typical
stages of cell division
21. What Causes Animals to Age
Ability of cells to continue to divide is limited
At the end of each chromosome in the nucleus there is
specific repeating DNA sequence called a telomere
Each time the cell divides some the of telomere is lost
As the animal ages the telomere becomes shorter and
eventually the cell stops dividing
This causes the animal to eventually die of old age if it
doesn’t die of some other cause first
22. Meiosis
When cells divide by mitosis the daughter cells contain two of each
type of chromosome, they are diploid
Reproductive cells are called gametes
The male gametes is the sperm, the female gamete is the egg
When the sperm and egg unite they form a zygote
If each gamete were diploid the zygote would have twice as many
chromosomes as the parents, since that can not be there is a
mechanisms that reduces the number of chromosomes in the
gametes by one-half
This specialized type of cell division is called meiosis.
23. What Happens During Meiosis?
Chromosome pairs are divided so that each gamete has
one of each type of chromosome
The gamete cell has a haploid number of chromosomes
The zygote that results from the union of the gametes has a
diploid number of chromosomes
24. Fertilization
Takes place when a sperm cell from a male reaches the
egg cell of a female
The two haploid cells (the sperm and the egg) unite and
form one complete cell or zygote
Zygote is diploid, it has a full set of chromosome pairs
This results in many different combinations of traits in
offspring
26. Genes
Pass heritable characteristics from one animal to another
Located on the chromosomes
Composed of DNA
Occur in pairs just like the chromosome
Gene pairs that are identical are homozygous and they control the
trait in the same way
If the gene pairs code for different expression of the same trait they
are heterozygous and the genes are called alleles
For example one gene may code for black and another for red.
The same trait is being affected but the alleles are coding for different
effects
Genotype is the combination of genes that an individual poses
27. Genes
Provide the code for the synthesis of enzymes and other proteins that
control the chemical reactions in the body
These reactions determine the physical characteristics
The physical appearance of an animal, insofar as its appearance is
determined by its genotype, is referred to as its phenotype
Environmental conditions can also influence physical characteristics
For example; the genotype of a beef animal for rate of gain determines a range
for that characteristic in which it will fall but the ration the animal receives will
determine where it actually falls in that range.
28. Genes
Some traits controlled by a singe pair
Most traits however are controlled by many pairs
Carcass traits, growth rate, feed efficiency are all controlled by
many gene pairs
30. Dominant and Recessive Genes
In a heterozygous pair the dominant gene hides the effect
of its allele
The hidden allele is called a recessive gene
When working problems involving genetic inheritance the
dominant gene is usually written as a capital letter and the
recessive gene is written as a lowercase letter
For example the polled condition in cattle is said to be
dominant so it would be written as Pp
31. Example Dominant & Recessive
Traits
Black is dominant to red in cattle
White face is dominant to color face in cattle
Black is dominant to brown in horses
Color is dominant to albinism
Rose comb is dominant to single comb (chicken)
Pea comb in chickens is dominant to single comb
Barred feather pattern in chickens is dominant to nonbarred
feather—the dominant gene is also sex-linked
Normal size in cattle is dominant to “snorter” dwarfism
32. Homozygous Gene Pairs
Homozygous gene pair carries two genes for a trait
For example a polled cow might carry a gene pair PP or a horned
cow must carry the gene pair pp
For a cow to have horns she must carry two recessive genes
33. Heterozygous Gene Pairs
Carry two different genes (alleles)
For example a polled cow may carry the gene pair Pp
34. Six Basic Crosses
Homozygous x Homozygous (PP x PP) (Both Dominant)
Heterozygous x Heterozygous (Pp x Pp)
Homozygous x Heterozygous (PP x Pp)
Homozygous (dominant) x Homozygous (recessive)
(PPxpp)
Heterozygous x Homozygous (recessive) (Pp x pp)
Homozygous (recessive) x Homozygous (recessive) (pp x
pp)
35. Predicting Results
Punnett Square
Male gametes on top
Female gametes on the left Male Gametes
side
P P
Female Gametes
P PP PP
P PP PP
36. Multiple Gene Pairs
When you have more than 1 gene combination you must
account for all the possible combinations
For example you are crossing a polled black bull (PpBb)
and a polled black cow (PpBb) both are heterozygous for
polledness and color
38. Incomplete Dominance
Occurs when the alleles at a gene locus are only partially
expressed
Usually produces a phenotype in the offspring that is
intermediate between the phenotypes that either allele
would express
39. Codominance
Occurs when neither allele in a R R
heterozygous condition
dominanates the other and W RW RW
both are fully expressed
Example W RW RW
Roan color in Shorthorn Cattle
R W
R RR RW
W RW WW
40. Sex-Limited Genes
The phenotypic expression of some genes is determined by
the presence or absence of one of the sex hormones
Limited to one sex
Example: Plumage patterns in male and female chickens
Males neck and tail feathers are long, pointed and curving
41. Sex-Influenced Genes
Some traits are expressed in one sex and recessive in the
other
In humans male pattern baldness is an example
In animals horns in sheep and color spotting in cattle
Horns are dominant in male sheep and recessive in females
42. Sex Determination: Mammals
Sex of the offspring is determined at X Y
fertilization
Female mammals have two sex
chromosomes in addition to the
regular chromosomes.
They are shown as XX X XX XY
Male mammals have only one sex
chromosome, the other chromosome
of the pair is shown as Y
Thus the male is XY
X XX XY
Sex of offspring is determined by the
male
43. Sex Determination: Birds X
Female determines the sex of Z Z
the offspring
Male carries two sex
chromosomes
Female carries one Z ZZ ZZ
After meiosis all the sperm
cells carry a Z chromosome
and only one-half of the egg
W ZW ZW
cells carry a Z, the other half
carry a W
44. Sex Linked Characteristics
Genes are only carried on sex b b
Z Z
chromosomes
Example is barred color in
chickens
Barred is dominant to black ZB ZB Z b ZB Z b
Result of crossing a barred
female ZB W with a black male
b b
Z Z
W Z bW Zb W
45. Linkage
Tendency for certain traits to stay together in the offspring
The closer the genes are located together on a
chromosome the more likely they are to stay together
46. Crossover
May result in the predictions of mating not always
happening
During one stage of meiosis the chromosomes line up very
close together. Sometimes the chromosomes cross over
one another and split
This forms new chromosomes with different combinations
of genes
The farther apart two genes are on a chromosomes the
more likely they are end up in new combination
47. Mutation
Generally genes are not changed from parent to offspring
However, sometimes something happens that causes genes to
change
When a new trait is shown which did not exist in either parent is
called mutation
Radiation will cause genes to mutate
Some mutations are beneficial, some harmful and other are of no
importance
Very few mutations occur and are not depended on for animal
improvement
Polled Hereford cattle are thought to be the result of a genetic
mutation
48. Summary
Livestock improvement is the result of using the principles of genetics
Gregor Mendel is considered the father of genetics
The amount of difference between parents and offspring is caused by genetics and
the environment
Heritability estimates are used to show how much of a difference in some traits
might come from genetics
Animals grow by cell division
Ordinary cell division is called mitosis
During mitosis each new cell is exactly like the old cell
Reproductive cells are called gametes
Gametes divide by meiosis
Male gamete is the sperm
Female gamete is the egg
49. Summary
Fertilization occurs when the sperm cell penetrates the egg and the chromosome
pairs are formed again when fertilization takes place
Genes control an animals traits
Some genes are dominant and some are recessive
Animals may carry two dominant or two recessive genes for a trait. They are
called homozygous pairs
Animals may also carry a dominant and recessive gene pair. They are called
heterozygous pairs
Sex of mammals is determined by the male
Sex of birds is determined by the female
Some characteristics are sex linked and are located on the sex chromosome
Crossover occurs when chromosomes exchange genes
Genes are sometimes changed by mutation and they are of little value in improving
livestock