Gregor Mendel conducted experiments breeding pea plants and discovered the laws of inheritance. He found that hereditary factors, now known as genes, are inherited in pairs and segregate independently during gamete formation. These genes can be dominant or recessive, and their combinations in offspring follow predictable patterns. Mendel's work disproved the blending theory of heredity and established the particulate theory that genes remain distinct during inheritance. His findings formed the foundation of classical genetics.
This document discusses chromosome and gene mapping techniques. It describes how gene mapping is used to identify the location of genes and distances between genes on chromosomes. Two main types of maps are discussed - genetic maps based on linkage and physical maps using actual distances in base pairs. Molecular markers are described as polymorphic DNA sequences used to map genes. Methods for genetic mapping like linkage analysis and calculating recombination fractions are explained.
This document discusses gene interaction, which refers to how two or more genes can affect the expression of a single trait in an organism. It begins by defining gene interaction and explaining that many traits are governed by multiple genes rather than a single gene. The document then outlines different types of gene interactions, including epistatic and hypostatic interactions. It classifies epistatic gene interactions into several categories based on how the genes influence each other, such as supplementary, complementary, inhibitory, duplicate, masking, and polymeric gene interactions. Examples are provided for each category to illustrate how the interaction modifies the dihybrid or trihybrid ratios.
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.
This document discusses different types of gene interaction, including allelic and non-allelic interaction. Allelic interaction includes complete dominance, incomplete dominance, and co-dominance. Non-allelic interaction includes complementary gene interaction, dominant and recessive epistasis, inhibitory gene interaction, and duplicate gene interaction. Examples are provided for each type of interaction, such as flower color in snapdragons and blood types in humans. Gene interaction occurs when the expression of one gene is influenced by one or more other genes.
This document discusses linkage and crossing over of genes. It explains that genes located on the same chromosome are linked, and the closer they are, the stronger the linkage. Crossing over occurs during meiosis and leads to recombination of genes from homologous chromosomes. Linkage maps can be constructed by observing the frequency of crossing over between linked gene loci. These maps show the linear order and genetic distances between genes on chromosomes.
Genes located on the same chromosome are linked and inherited together, forming a linkage group. Mendel's law of independent assortment does not apply to linked genes. During meiosis, linked genes may undergo crossing over, where portions of homologous chromosomes are exchanged. This can result in new combinations of alleles and the production of recombinant offspring that differ from their parents' genotypes. A test cross can be used to identify which offspring from a dihybrid cross involving linked genes are recombinants.
This document discusses chromosome and gene mapping techniques. It describes how gene mapping is used to identify the location of genes and distances between genes on chromosomes. Two main types of maps are discussed - genetic maps based on linkage and physical maps using actual distances in base pairs. Molecular markers are described as polymorphic DNA sequences used to map genes. Methods for genetic mapping like linkage analysis and calculating recombination fractions are explained.
This document discusses gene interaction, which refers to how two or more genes can affect the expression of a single trait in an organism. It begins by defining gene interaction and explaining that many traits are governed by multiple genes rather than a single gene. The document then outlines different types of gene interactions, including epistatic and hypostatic interactions. It classifies epistatic gene interactions into several categories based on how the genes influence each other, such as supplementary, complementary, inhibitory, duplicate, masking, and polymeric gene interactions. Examples are provided for each category to illustrate how the interaction modifies the dihybrid or trihybrid ratios.
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.
This document discusses different types of gene interaction, including allelic and non-allelic interaction. Allelic interaction includes complete dominance, incomplete dominance, and co-dominance. Non-allelic interaction includes complementary gene interaction, dominant and recessive epistasis, inhibitory gene interaction, and duplicate gene interaction. Examples are provided for each type of interaction, such as flower color in snapdragons and blood types in humans. Gene interaction occurs when the expression of one gene is influenced by one or more other genes.
This document discusses linkage and crossing over of genes. It explains that genes located on the same chromosome are linked, and the closer they are, the stronger the linkage. Crossing over occurs during meiosis and leads to recombination of genes from homologous chromosomes. Linkage maps can be constructed by observing the frequency of crossing over between linked gene loci. These maps show the linear order and genetic distances between genes on chromosomes.
Genes located on the same chromosome are linked and inherited together, forming a linkage group. Mendel's law of independent assortment does not apply to linked genes. During meiosis, linked genes may undergo crossing over, where portions of homologous chromosomes are exchanged. This can result in new combinations of alleles and the production of recombinant offspring that differ from their parents' genotypes. A test cross can be used to identify which offspring from a dihybrid cross involving linked genes are recombinants.
This document discusses quantitative inheritance, which refers to inheritance of traits that are influenced by multiple genes and the environment. Quantitative traits show continuous variation and are influenced by small effects from many genes. Examples discussed include human height, skin color, and kernel color in wheat. The kernel color experiment of Nilsson-Ehle is used to demonstrate quantitative inheritance. It involved crossing two wheat varieties and analyzing the ratios of kernel color phenotypes in the offspring. For the experiment to work well, the genes influencing color needed to have additive effects and the environment could not impact phenotypes. The experiment helped establish that quantitative traits are influenced by multiple independent gene loci.
Modification of Normal Mendelian ratios with Lethal gene effcets and EpistasisAashish Patel
This document discusses Mendelian genetics and how ratios from monohybrid and dihybrid crosses can be modified. It explains different types of gene interactions including incomplete dominance, codominance, lethal genes, and epistasis. Epistasis refers to interaction between alleles at different loci that modifies phenotypic ratios. Several examples are given to illustrate different types of epistatic interactions like recessive epistasis, dominant epistasis, and duplicate gene interactions. The document also provides tables comparing standard Mendelian ratios to ratios resulting from these various genetic modifications.
- Gregor Mendel, an Augustinian monk in the late 1800s, is considered the founder of genetics for his experiments breeding pea plants. He studied traits like flower color, seed texture, and pod shape.
- Mendel discovered that traits are passed from parents to offspring through discrete units called genes, located on chromosomes. Genes come in different forms called alleles that give rise to different traits.
- Through experiments breeding thousands of pea plants, Mendel determined that alleles segregate and assort independently during reproduction according to his laws of inheritance. This laid the foundation for modern genetics.
Genes located on the same chromosome tend to be inherited together due to their physical linkage on the chromosome. However, linkage can be broken during meiosis via recombination between homologous chromosomes through the process of crossover. Recombination results in new combinations of parental alleles and limits the types of gametes produced under conditions of complete linkage. Morgan's experiments with Drosophila provided evidence of this by demonstrating non-Mendelian inheritance ratios when genes were linked versus unlinked.
Molecular genetics: it deals with the structure, composition, function and replication of chromosomes and genes, representing genetics material like DNA and RNA.
MIC150 - Chap 2 Extension Of Mendelian GeneticsAlia Najiha
This document discusses extensions of Mendelian genetics beyond simple dominant-recessive inheritance. It introduces concepts like codominance, incomplete dominance, multiple alleles, lethal alleles, and linked genes. Codominance occurs when both alleles for a gene are fully expressed in the heterozygote. In incomplete dominance, the heterozygote exhibits an intermediate phenotype between the homozygotes. Multiple alleles exist at a single gene locus with more than two allelic forms. Lethal alleles cause death if homozygous. Linked genes tend to be inherited together due to their proximity on the same chromosome.
Polygenic inheritance involves multiple genes contributing to a trait, as opposed to single-gene inheritance. It can result in continuous variation, where a wide range of phenotypes exist between extremes. Human skin color and wheat seed color are examples of polygenic traits that show continuous variation, with skin color determined by 3-4 genes influencing melanin production and seed color by 3 genes determining red pigment levels.
This Power Point Presentation is designed to explain Mendel's experiment on hybridization and dihybrid cross which considers inheritance of two traits at a time and to know whether they are inherited independently or are influenced by each other and also about Law of Independent assortment
Mendel's work with pea plants in the mid-19th century laid the foundations of genetics by demonstrating that traits are passed from parents to offspring through discrete units of inheritance. During the early 20th century, scientists such as Morgan and Sutton connected Mendel's theories to chromosomes and the cellular basis of inheritance. The emergence of molecular genetics in the mid-20th century revealed that DNA carries the genetic information that is passed from cell to cell and between generations.
Gregor Mendel conducted experiments with pea plants to study inheritance of traits from one generation to the next. He found that traits are controlled by factors, now known as genes, that exist in different forms called alleles. In monohybrid crosses, he found that one allele can be dominant over the other in the first generation, but both alleles are passed down and segregate in a 3:1 ratio in the second generation. Mendel also discovered that genes for different traits assort independently during gamete formation according to his law of independent assortment.
Probability, Mendel, and Genetics PowerpointMrs. Henley
The document summarizes key concepts from Gregor Mendel's experiments with pea plants including:
- Mendel studied traits like plant height, seed shape and color in pea plants which existed in distinct forms (tall vs short, round vs wrinkled seeds)
- He performed controlled crosses between purebred (homozygous) pea plants and found that some traits were dominant over others in the offspring
- Mendel developed the concepts of dominant and recessive alleles and used Punnett squares to predict the probabilities of traits being expressed in offspring
Incomplete dominance results in a blending of the dominant and recessive alleles such that the phenotype is intermediate between the two pure phenotypes. Codominance results in both alleles being fully expressed together in the heterozygote such that the phenotype shows a combination of both. Examples include snapdragons that are pink when heterozygous for red and white alleles under incomplete dominance, and human blood types that are type AB when heterozygous for the A and B alleles under codominance.
This document discusses different concepts of genes including:
1. Classical concepts viewed genes as units of heredity, transmission of characters, and mutation.
2. Molecular concepts define genes as the entire nucleic acid sequence required for protein synthesis, including coding and regulatory regions.
3. Genes have a fine structure and can be divided into functional units called cistrons based on complementation testing of mutants.
1) Mendel conducted breeding experiments with pea plants over 10 years to study inheritance of traits from parents to offspring.
2) He found that some traits are dominant and others recessive, with dominant traits masking recessive traits in the first filial generation.
3) Mendel also discovered that traits are inherited independently according to his Law of Independent Assortment.
The document discusses probability and genetics. It explains that Mendel's laws of segregation and independent assortment reflect the same laws of probability that apply to events like coin tosses or dice rolls. It then provides examples of how to calculate genetic probabilities, such as there being a 50% chance of a dominant trait being passed on, in the same way there is a 50% chance of tossing heads. The rule of multiplication is discussed, stating that the probability of two independent events occurring together is the probabilities multiplied. Examples of applying this to dihybrid crosses and calculating probabilities are also given.
1. Genetic linkage occurs when two genes located near each other on the same chromosome tend to be inherited together during meiosis.
2. Early theories of linkage proposed by Sutton, Boveri, Bateson and Punnett failed to fully explain observed inheritance patterns.
3. Morgan's chromosomal theory of linkage established that genes are linearly arranged on chromosomes and that the closer two genes are, the stronger the tendency for them to be inherited together. This provided an explanation for linkage patterns and laid the foundation for modern genetics.
Gene interactions play an important role in inheritance and can produce phenotypes that do not follow typical Mendelian ratios. There are two main types of gene interactions - allelic and non-allelic. Allelic interactions occur between alleles of the same gene and can be complete dominance, incomplete dominance, or co-dominance. Non-allelic interactions occur between genes and can be simple interactions like those controlling comb patterns in chickens, or more complex interactions like epistasis where one gene suppresses the expression of another. Understanding gene interactions is crucial for explaining exceptions to Mendelian inheritance.
This document discusses three genetic inheritance patterns: dominance, incomplete dominance, and co-dominance. Dominance occurs when one allele is expressed over the other. In incomplete dominance, the heterozygous phenotype is intermediate between the two homozygous phenotypes. Examples include flowers and hair color. Co-dominance occurs when both alleles are fully expressed in the heterozygote, so the phenotype shows traits of both. Examples given are coat color in horses and cattle, and chestnut and white coat colors producing a palomino horse.
GENETICS - Dr. P. Saranraj, Assistant Professor, Department of Microbiology, Sacred Heart College (Autonomous), Tirupattur, Vellore District, Tamil Nadu, India
This document defines key terms related to Mendelian genetics and inheritance. It describes Mendel's experiments with pea plants and his conclusions, including his laws of inheritance. Specifically, it discusses Mendel's work on monohybrid crosses and the 3:1 ratio of traits in the F2 generation. It also introduces the chromosomal theory of inheritance proposed by Sutton and Boveri, which linked genes to chromosomes. Finally, it covers the concept of genetic linkage discovered by Morgan, where genes located near each other on the same chromosome tend to be inherited together.
Gregor Mendel conducted the first recorded scientific study of heredity by breeding pea plants. Through his experiments, he discovered that traits are passed from parents to offspring through discrete units (now known as genes). Mendel determined that some traits are dominant and will mask recessive traits, and that traits are inherited independently of each other. His work established the basic principles of genetics and heredity.
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This document discusses quantitative inheritance, which refers to inheritance of traits that are influenced by multiple genes and the environment. Quantitative traits show continuous variation and are influenced by small effects from many genes. Examples discussed include human height, skin color, and kernel color in wheat. The kernel color experiment of Nilsson-Ehle is used to demonstrate quantitative inheritance. It involved crossing two wheat varieties and analyzing the ratios of kernel color phenotypes in the offspring. For the experiment to work well, the genes influencing color needed to have additive effects and the environment could not impact phenotypes. The experiment helped establish that quantitative traits are influenced by multiple independent gene loci.
Modification of Normal Mendelian ratios with Lethal gene effcets and EpistasisAashish Patel
This document discusses Mendelian genetics and how ratios from monohybrid and dihybrid crosses can be modified. It explains different types of gene interactions including incomplete dominance, codominance, lethal genes, and epistasis. Epistasis refers to interaction between alleles at different loci that modifies phenotypic ratios. Several examples are given to illustrate different types of epistatic interactions like recessive epistasis, dominant epistasis, and duplicate gene interactions. The document also provides tables comparing standard Mendelian ratios to ratios resulting from these various genetic modifications.
- Gregor Mendel, an Augustinian monk in the late 1800s, is considered the founder of genetics for his experiments breeding pea plants. He studied traits like flower color, seed texture, and pod shape.
- Mendel discovered that traits are passed from parents to offspring through discrete units called genes, located on chromosomes. Genes come in different forms called alleles that give rise to different traits.
- Through experiments breeding thousands of pea plants, Mendel determined that alleles segregate and assort independently during reproduction according to his laws of inheritance. This laid the foundation for modern genetics.
Genes located on the same chromosome tend to be inherited together due to their physical linkage on the chromosome. However, linkage can be broken during meiosis via recombination between homologous chromosomes through the process of crossover. Recombination results in new combinations of parental alleles and limits the types of gametes produced under conditions of complete linkage. Morgan's experiments with Drosophila provided evidence of this by demonstrating non-Mendelian inheritance ratios when genes were linked versus unlinked.
Molecular genetics: it deals with the structure, composition, function and replication of chromosomes and genes, representing genetics material like DNA and RNA.
MIC150 - Chap 2 Extension Of Mendelian GeneticsAlia Najiha
This document discusses extensions of Mendelian genetics beyond simple dominant-recessive inheritance. It introduces concepts like codominance, incomplete dominance, multiple alleles, lethal alleles, and linked genes. Codominance occurs when both alleles for a gene are fully expressed in the heterozygote. In incomplete dominance, the heterozygote exhibits an intermediate phenotype between the homozygotes. Multiple alleles exist at a single gene locus with more than two allelic forms. Lethal alleles cause death if homozygous. Linked genes tend to be inherited together due to their proximity on the same chromosome.
Polygenic inheritance involves multiple genes contributing to a trait, as opposed to single-gene inheritance. It can result in continuous variation, where a wide range of phenotypes exist between extremes. Human skin color and wheat seed color are examples of polygenic traits that show continuous variation, with skin color determined by 3-4 genes influencing melanin production and seed color by 3 genes determining red pigment levels.
This Power Point Presentation is designed to explain Mendel's experiment on hybridization and dihybrid cross which considers inheritance of two traits at a time and to know whether they are inherited independently or are influenced by each other and also about Law of Independent assortment
Mendel's work with pea plants in the mid-19th century laid the foundations of genetics by demonstrating that traits are passed from parents to offspring through discrete units of inheritance. During the early 20th century, scientists such as Morgan and Sutton connected Mendel's theories to chromosomes and the cellular basis of inheritance. The emergence of molecular genetics in the mid-20th century revealed that DNA carries the genetic information that is passed from cell to cell and between generations.
Gregor Mendel conducted experiments with pea plants to study inheritance of traits from one generation to the next. He found that traits are controlled by factors, now known as genes, that exist in different forms called alleles. In monohybrid crosses, he found that one allele can be dominant over the other in the first generation, but both alleles are passed down and segregate in a 3:1 ratio in the second generation. Mendel also discovered that genes for different traits assort independently during gamete formation according to his law of independent assortment.
Probability, Mendel, and Genetics PowerpointMrs. Henley
The document summarizes key concepts from Gregor Mendel's experiments with pea plants including:
- Mendel studied traits like plant height, seed shape and color in pea plants which existed in distinct forms (tall vs short, round vs wrinkled seeds)
- He performed controlled crosses between purebred (homozygous) pea plants and found that some traits were dominant over others in the offspring
- Mendel developed the concepts of dominant and recessive alleles and used Punnett squares to predict the probabilities of traits being expressed in offspring
Incomplete dominance results in a blending of the dominant and recessive alleles such that the phenotype is intermediate between the two pure phenotypes. Codominance results in both alleles being fully expressed together in the heterozygote such that the phenotype shows a combination of both. Examples include snapdragons that are pink when heterozygous for red and white alleles under incomplete dominance, and human blood types that are type AB when heterozygous for the A and B alleles under codominance.
This document discusses different concepts of genes including:
1. Classical concepts viewed genes as units of heredity, transmission of characters, and mutation.
2. Molecular concepts define genes as the entire nucleic acid sequence required for protein synthesis, including coding and regulatory regions.
3. Genes have a fine structure and can be divided into functional units called cistrons based on complementation testing of mutants.
1) Mendel conducted breeding experiments with pea plants over 10 years to study inheritance of traits from parents to offspring.
2) He found that some traits are dominant and others recessive, with dominant traits masking recessive traits in the first filial generation.
3) Mendel also discovered that traits are inherited independently according to his Law of Independent Assortment.
The document discusses probability and genetics. It explains that Mendel's laws of segregation and independent assortment reflect the same laws of probability that apply to events like coin tosses or dice rolls. It then provides examples of how to calculate genetic probabilities, such as there being a 50% chance of a dominant trait being passed on, in the same way there is a 50% chance of tossing heads. The rule of multiplication is discussed, stating that the probability of two independent events occurring together is the probabilities multiplied. Examples of applying this to dihybrid crosses and calculating probabilities are also given.
1. Genetic linkage occurs when two genes located near each other on the same chromosome tend to be inherited together during meiosis.
2. Early theories of linkage proposed by Sutton, Boveri, Bateson and Punnett failed to fully explain observed inheritance patterns.
3. Morgan's chromosomal theory of linkage established that genes are linearly arranged on chromosomes and that the closer two genes are, the stronger the tendency for them to be inherited together. This provided an explanation for linkage patterns and laid the foundation for modern genetics.
Gene interactions play an important role in inheritance and can produce phenotypes that do not follow typical Mendelian ratios. There are two main types of gene interactions - allelic and non-allelic. Allelic interactions occur between alleles of the same gene and can be complete dominance, incomplete dominance, or co-dominance. Non-allelic interactions occur between genes and can be simple interactions like those controlling comb patterns in chickens, or more complex interactions like epistasis where one gene suppresses the expression of another. Understanding gene interactions is crucial for explaining exceptions to Mendelian inheritance.
This document discusses three genetic inheritance patterns: dominance, incomplete dominance, and co-dominance. Dominance occurs when one allele is expressed over the other. In incomplete dominance, the heterozygous phenotype is intermediate between the two homozygous phenotypes. Examples include flowers and hair color. Co-dominance occurs when both alleles are fully expressed in the heterozygote, so the phenotype shows traits of both. Examples given are coat color in horses and cattle, and chestnut and white coat colors producing a palomino horse.
GENETICS - Dr. P. Saranraj, Assistant Professor, Department of Microbiology, Sacred Heart College (Autonomous), Tirupattur, Vellore District, Tamil Nadu, India
This document defines key terms related to Mendelian genetics and inheritance. It describes Mendel's experiments with pea plants and his conclusions, including his laws of inheritance. Specifically, it discusses Mendel's work on monohybrid crosses and the 3:1 ratio of traits in the F2 generation. It also introduces the chromosomal theory of inheritance proposed by Sutton and Boveri, which linked genes to chromosomes. Finally, it covers the concept of genetic linkage discovered by Morgan, where genes located near each other on the same chromosome tend to be inherited together.
Gregor Mendel conducted the first recorded scientific study of heredity by breeding pea plants. Through his experiments, he discovered that traits are passed from parents to offspring through discrete units (now known as genes). Mendel determined that some traits are dominant and will mask recessive traits, and that traits are inherited independently of each other. His work established the basic principles of genetics and heredity.
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Genetics is the study of genes, heredity, and genetic variation. Gregor Mendel conducted experiments with pea plants in the 1800s and established the principles of inheritance, including dominance, segregation, and independent assortment. His work showed that traits are passed from parents to offspring through discrete units called genes. Monohybrid and dihybrid crosses examine the inheritance of one or two traits and can be represented using Punnett squares. Mendel's principles form the basis of modern genetics.
Gregor Mendel conducted experiments crossing pea plants with different traits like stem height, seed coat color, etc. He discovered three laws of inheritance:
1) Law of Dominance: Dominant traits will be expressed in the offspring while recessive traits will not.
2) Law of Segregation: Alleles segregate so each gamete contains only one of the two alleles.
3) Law of Independent Assortment: Alleles of different traits assort independently, resulting in new trait combinations in offspring.
1. Gregor Mendel discovered genetics through experiments with pea plants. He found that traits separated and assorted independently during reproduction according to his laws of inheritance.
2. Genes determine traits and exist in different alleles that are passed from parents to offspring. Dominant alleles will be expressed over recessive alleles.
3. Mendel's experiments showed monohybrid and dihybrid inheritance followed predictable ratios through the generations. His work formed the foundations of classical genetics.
Gregor Mendel was an Augustinian monk who conducted breeding experiments with pea plants in the 1850s and 1860s. He studied seven traits in peas and found that traits are passed to offspring through discrete "factors" (now called genes). Mendel discovered that these factors segregate and assort independently during reproduction, resulting in predictable inheritance patterns. His work established the foundations of genetics but was not widely accepted until the early 20th century.
The document summarizes Gregor Mendel's experiments with pea plants that laid the foundation for the modern understanding of genetics and heredity. It discusses Mendel's observations of inherited traits in pea plants and how this led him to discover the three laws of inheritance: 1) the law of dominance, 2) the law of segregation, and 3) the law of independent assortment. It also explains some of Mendel's experimental methods and variables he controlled that contributed to his success, such as choosing simple and contrasting traits to study. Finally, it provides examples of genetic crosses and inheritance patterns including monohybrid and dihybrid crosses using Punnett squares.
Gregor Mendel conducted experiments with pea plants between 1856-1863. He found that traits from parents separate and pass to offspring independently. His laws of inheritance established that dominant traits are expressed over recessive in hybrids, but recessive traits can be expressed in later generations. The laws of dominance, segregation, and independent assortment showed that traits are controlled by discrete factors (now called genes) that segregate and sort independently during reproduction. Mendel's discoveries formed the foundation of classical genetics and heredity.
Mendelian Inheritance and Post-Mendelian Developments.pptxBhanu Yadav
This Project Aims at discussing Mendel's Laws of Inheritance with a brief introduction to his work, followed up by the developments that occured post mendelism
1. A Punnett square is used to predict the possible combinations of alleles in offspring from known parental genotypes. It represents the gametes and possible zygotes from a genetic cross.
2. A Punnett square example shows a cross between a heterozygous parent (Tt) and a homozygous recessive parent (tt). It predicts that the offspring will be in a 3:1 ratio of tall to short phenotypes.
3. Probabilities from Punnett squares predict averages over many genetic crosses, not the exact outcomes of individual crosses, which may vary. The more offspring, the closer the observed ratios will be to the expected probabilities.
This document discusses the history and foundations of genetics. It describes Gregor Mendel, considered the father of genetics, and his experiments breeding pea plants in the mid-1800s. Mendel's experiments led him to propose his laws of inheritance and established the basic principles of heredity and traits being passed from parents to offspring. The document outlines Mendel's experimental methods, observations of traits being dominant or recessive between generations, and his conclusions regarding inheritance being governed by discrete factors (now known as genes) and principles of segregation and independent assortment.
Genetics
-. Basic Principles of Mendelian Genetics and Patterns of Inheritance
-Molecular Genetics & Inheritance
-. Protein Synthesis
- Mutations
-. Manipulation of DNA
-. ABO blood groups and Rh Factors
Evolution
- Theories on the origin of life on Earth
-. Theories of Evolution
Gregor Mendel conducted early experiments in genetics using pea plants. He discovered two laws of heredity:
1) The Law of Segregation states that alleles for a trait separate during gamete formation so each gamete carries one allele.
2) The Law of Independent Assortment states that each trait assorts independently of other traits during gamete formation.
Through his experiments, Mendel established the foundations of classical genetics and heredible traits being passed from parents to offspring via discrete units now known as genes.
This document provides background information on Gregor Mendel and his experiments with pea plants that formed the basis of genetics. It discusses Mendel's education and career as a monk, his selection of pea plants as an experimental organism, his monohybrid and dihybrid cross experiments, and his formulation of Mendel's laws of inheritance. Key points include that Mendel conducted experiments over many generations of pea plants to study inheritance of traits like plant height and seed color, and from this work deduced the laws of dominance, segregation, and independent assortment.
This pdf comprises of Basic of Genetics: Purpose: To convey that “Genetics is to biology what Newton’s
laws are to Physical Sciences”. Mendel’s laws, Concept of segregation and
independent assortment. Concept of allele. Gene mapping, Gene
interaction, Epistasis. Meiosis and Mitosis be taught as a part of
genetics. Emphasis to be give not to the mechanics of cell division nor the
phases but how genetic material passes from parent to offspring. Concepts
of recessiveness and dominance. Concept of mapping of phenotype to
genes. Discuss about the single gene disorders in humans. Discuss the
concept of complementation using human genetics.
This document provides information about heredity and evolution. It discusses Gregor Mendel's experiments with pea plants which laid the foundation for genetics through his laws of inheritance. It describes how Mendel conducted monohybrid crosses to study the inheritance of single traits. The document also discusses Charles Darwin's theory of natural selection and how it led to the concept of evolution. It provides a brief overview of human evolution and the development of early humans from hominids to Homo sapiens. The key techniques of genetic engineering like restriction enzymes and DNA ligases are also summarized.
Gregor Mendel conducted experiments with pea plants to study inheritance of traits. He found that traits are inherited as discrete units (now known as genes) that are passed from parents to offspring. These genes come in pairs and one gene is dominant while the other is recessive. Through his experiments with monohybrid and dihybrid crosses, Mendel deduced the laws of inheritance including dominance, segregation, and independent assortment. His work established the foundations of classical genetics.
- Mendel conducted experiments with pea plants involving monohybrid and dihybrid crosses to study inheritance of traits.
- In monohybrid crosses, he studied inheritance of one trait (e.g. plant height) between pure-breeding tall and dwarf pea plants. His results supported laws of dominance, segregation, and independent assortment.
- In dihybrid crosses, he studied inheritance of two traits (e.g. seed shape and color) and found offspring exhibited four phenotypes in a 9:3:3:1 ratio, supporting independent assortment of genes.
- Mendel's experiments were pioneering in establishing basic principles of genetics and heredity.
LIKE BEGETS LIKE, which means young one resemble their parents, (MONOHYBRID CROSS & DIHYBRID CROSS) is the well-known dogma associated with heredity. Each species has similarities among themselves due to the cause of heredity. W.Bateson was the first one to coin the term genetics in 1905. It is derived from the greek word “genesis” means to grow into or to become . in other word, genetics is the study of heredity and variation.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
The simplified electron and muon model, Oscillating Spacetime: The Foundation...RitikBhardwaj56
Discover the Simplified Electron and Muon Model: A New Wave-Based Approach to Understanding Particles delves into a groundbreaking theory that presents electrons and muons as rotating soliton waves within oscillating spacetime. Geared towards students, researchers, and science buffs, this book breaks down complex ideas into simple explanations. It covers topics such as electron waves, temporal dynamics, and the implications of this model on particle physics. With clear illustrations and easy-to-follow explanations, readers will gain a new outlook on the universe's fundamental nature.
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Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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2. Genetics
• Genetics is a branch of biology concerned with the study of genes,
genetic variation, and heredity in organisms.
• Gene is a unit of heredity which is transferred from a parent to
offspring and is held to determine some characteristic of the
offspring.
2
3. Brief Life Sketch of Gregor Johann Mendel
• Gregor Mendel (1822-1884), who is called the father of genetics, was
born in a poor farmer family of Austria.
• After completing education up to secondary school, he joined a
monastery during 1843, and on his 25th birthday he became a monk.
• Mendel conducted hybridization work on various plants, i.e.,
snapdragon, pumpkin, flax, bean, pea, plum, pear, maize, etc.
3
4. • He was sent to Vienna University during 1851 to study science and
mathematics.
• On his return to Brunn (1854), in addition to his duties as priest, he was
appointed as a substitute teacher in a school.
• He collected garden pea seed from the market during 1857 and started
regular hybridization work and was thus able to present his results before
the History Society of Brunn in 1865.
• Results were published in 1866 and were sent to various countries.
• His work remained unnoticed for a period of 34 years.
• In 1900 three biologists, Correns, de Vries, and Tschermak read Mendel’s
forgotten paper and also obtained the similar results from their own
experiments.
4
5. Mendel’s choice of pea plant was not a mere chance, but was based on
these facts:
i. Many pure-breeding pea varieties were available
ii. Floral structure and mode of pollination in pea ensures self-
pollination and
iii. Hybrids are fertile.
He finally selected the following seven easily recognizable contrasting
characters:
5
6. Pea-plant characters studied by Mendel
No. Character Dominant
1. Tall versus dwarf vine Tall
2. Green versus yellow color of unripe pods Green
3. Inflated versus Constricted pods Inflated
4. Axillary versus terminal flowers Axillary (Axial)
5. Yellow versus green endosperm (Cotyledon) Yellow
6. Round versus wrinkled seed surface Round
7. Purple versus white flower color Purple
6
7. • Mendel made several crosses of pea plants having contrasting
characters to find out how the hereditary elements behaved while
passing from parents to offspring.
• We shall consider here only one or two of the several experiments
that he performed.
7
8. • Mendel crossed a tall pea plant with a dwarf one and observed that
all the resulting hybrid plants (F1) were tall.
• F1 plants were self-fertilized to produce F2 seed which was planted to
study the behavior of the F2 generation.
• Mendel noted that of all the F2 plants,
• 3/4 plants were tall and
• 1/4 plants were dwarf.
8
9. It may be pointed out here that
• The outward expression of a character later came to be referred to as
“phenotype” and
• The complex of genetic factors controlling this expression as
“genotype”.
9
12. When Mendel self-crossed these F2 plants, he observed that
• The dwarf plants, which were ¼ of the total F2 population, produced
all dwarfs, while
• Out of the ¾ tall plants,
• 1/3 produced all tall and
• 2/3 produced both tall and dwarf plants:
that is precisely what was expected from the genotypes contained in
the F2 population above.
12
13. Law of Segregation
• All other 6 characters behaved in the similar manner in crosses. From
this, Mendel formulated his first law of inheritance: the law of
Segregation or Mendel’s first law of inheritance.
• It states that “Heredity characters are determined by some particular
factors (genes) which occur in pairs and at the time of gamete
formation these factors segregate at random so that only one
member of a gene pair is transmitted to a particular gamete”
13
14. Dominance
• The other important phenomenon which Mendel discovered was that of
dominance. He noticed that the hybrids (F1’s) (Tt) between tall and dwarf
were all tall like the tall parent, although it also inherited the dwarf factor.
• The factor which dominated the effect of the other allele in the F1 was
designated by Mendel as dominant and the alternative factor that
remained latent in F1 as recessive.
He showed
• Dominant characters by the use of capital letters and
• Recessive by small letters
14
15. Mendel’s law of segregation and its explanation
• Mendel’s first law of inheritance is the law of segregation, which
explains the behavior of alleles of a gene pair in a diploid organism at
gamete formation.
• According to this law, the two alleles which may be identical or
dissimilar i.e. AA, aa or Aa segregate by going to different poles in
meiotic divisions and thus end up into different gametes.
• Note that segregation of alleles occurs during the meiotic divisions.
15
16. • Consider a cross between two true-breeding plants.
• One of them is tall and the other dwarf.
• Because both of them are diploid, each has a pair of alleles.
• The tall one has both the alleles, T, T and the dwarf one has both its
alleles, t, t.
• The gametes which they will produce will have one allele only as the
number is reduced to one half.
• We shall get a gamete of ‘T’ constitution from one parent and a
gamete of ‘t’ constitution from the other.
16
17. • They reunite and their reunion is called fertilization.
• The new plant produced by the union of T and t will be Tt.
• This means that the new hybrid plant has two alleles but they are not
alike, as one of them is T (for tallness) and the other is t (for
dwarfness).
• If the hybrid plant is tall, we will be able to say that the character
tallness controlled by ‘T’ is dominant over the corresponding
contrasting character, dwarfness, controlled by ‘t’.
17
18. • Further, when this hybrid plant Tt matures and forms gametes, the two
alleles T and t, carried on the two homologous chromosomes, cannot stay
together, because the homologous chromosomes must go to the opposite
poles in meiotic division and so will the two contrasting alleles.
• This going of the two alleles to the opposite poles in meiosis provides the
mechanism for segregation of the alleles of the same gene pairs.
• Consequently, two types of gametes, T and t are formed by the hybrid plant
in its male and female reproductive organs.
• Their reunion will produce these off springs
1 TT : 2 Tt : 1 tt
18
20. • From this discussion, it is apparent that the two alleles remain
together in a diploid individual and segregate when that individual
forms gametes and again come together in various combinations
when male and female gametes unite to produce new individuals.
20
21. Mendel’s Second Law of Inheritance or
Mendel’s Law of Independent Assortment
• We may now consider two characters together as to their behavior in
inheritance.
• For instance, Mendel crossed a tall plant having axillary flowers with a
dwarf plant having terminal flower.
• As ‘T’ and ‘t’ represent tallness and dwarfness, respectively, and
• Let ‘A’ and ‘a’ represent axillary and terminal flower positions, respectively.
21
22. We may write the cross as follows:
Parents Tall Axillary x Dwarf Terminal
TTAA ttaa
Gametes TA ta
F1 TtAa (Tall with Axillary flowers)
22
23. F1 plants (TtAa) will produce these four types of gametes TA, Ta, tA, ta,
in equal proportion.
The four types of gametes will be male as well as female and their
random union will produce 16 combinations in the next generation (F2).
23
24. TTAA TTAa TtAA TtAa
TTAa TTaa TtAa Ttaa
TtAA TtAa ttAA ttAa
TtAa Ttaa ttAa ttaa
Tall/Axillary: 9
Tall/Terminal: 3
Dwarf/Axillary: 3
Dwarf/Terminal: 1
9:3:3:1 phenotypic ratio
TA Ta tA ta
TA
Ta
tA
ta
F1 TtAa
Gametes TA, Ta, tA, ta
Male Gametes
Female
Gametes
24
25. Mendel noted that all F1’s were tall with axillary flowers where from he
confirmed that
• Tall was dominant over dwarf and
• Axillary flower over terminal flower
Out of these 16 combinations of the F2,
• 9 were tall with axillary flowers,
• 3 were tall with terminal flowers,
• 3 were dwarf with axillary flowers and only
• 1 was dwarf with terminal flowers.
25
26. It may be seen that, as the
• 9 tall axillary-flowered plants have at least one ‘T’ and one ‘A’, these
show both the dominant characters,
• 3 have ‘T’ but no ‘A’ they show one dominant character, other
• 3 have ‘A’ but no ‘T’, and they show the other dominant character,
• 1 has neither ‘T’ nor ‘A’ but is ttaa and is double recessive.
26
27. Explanation.
• It will be noticed that when the F1 hybrid plant, TtAa, matures, it
forms four types of gametes (pollens as well as ovules).
• ‘T’ and ‘t’ are the two members of an allelic pair and gametes are
formed as a result of meiotic divisions whereby the two alleles must
segregate.
• In the case of the hybrid plant TtAa, ‘T’ and ‘t’ must segregate, i.e
they must not be present in the same gamete.
• Similarly, ‘A’ and ‘a’ must segregate and go to different gametes.
27
28. • But while the two members of a given allelic pair must segregate they
do so independently of the members that is, if ‘T’ goes to one pole,
either ‘A’ or ‘a’ of the allelic pair Aa, can go with ‘T’ to the same pole.
• So the resulting gamete (pollen or ovule can have ‘T’ with ‘A’ (TA) or
‘T’ with ‘a’ (Ta).
• Similarly, the gamete produced at the other pole can have ‘t’ with ‘A’
(tA) or ‘t’ with ‘a’ (ta).
28
29. • Accordingly, this plant, TtAa, must produce four types of gametes, i.e.,
(TA), (Ta), (tA) and (ta) in equal proportion.
• This is actually what the plant does.
29
30. • The production of these four types of gametes in equal numbers is
possible only if the two gene pairs, Tt and Aa assort independently of
each other.
• This phenomenon is called “Independent Assortment” of characters,
the Second Mendelian Law.
• If the four types of gametes, male as well as female, unite at random
in the process of fertilization, 16 F2 combinations as shown above
should be possible.
30
31. Back-cross and Test cross
• When F1 hybrid is crossed with one of its parents, it is called a
backcross.
• When the cross involves the recessive parents it is called a test cross.
31
32. • Test crosses are used to test an individual's genotype by crossing it with an
individual of a known genotype.
• Individuals that show the recessive phenotype are known to have a homozygous
recessive genotype.
• Individuals that show the dominant phenotype, however, may either be
homozygous dominant or heterozygous.
• The phenotypically dominant organism is the individual in question in a test cross.
• The purpose of a test cross is to determine if this individual is homozygous
dominant or heterozygous
32
33. • We may remember that the F1 hybrid between Mendel’s tall and
dwarf pea plants were all tall, which may be crossed with dwarf
recessive (tt) parent to form a test cross.
• The hybrid tall parent (Tt) would produce equal number of ‘T’ and ‘t’
gametes and the dwarf being homozygous should form only one type
of gametes, i.e., ‘t’.
• Half the ovules of the genotype, ‘T’ when fertilized by ‘t’ pollen will
produce ‘Tt’ plants and the other half ovules of t genotype fertilized
by ‘t’ pollen produce ‘tt’ plants.
33
34. • A definite ratio of 1/2 tall and 1/2 dwarf plants would thus be
obtained.
• The 1:1 ratio based on theoretical calculations was confirmed by
Mendel through such experiments.
• Mendel clearly demonstrated that the characters are determined by
particulate factors which do not blend with or contaminate one
another during the course of their transmission from generation to
generation.
34
36. 36
F1 x dwarf recessive parent F1 x Dwarf Parent
Tt tt
Gametes T, t t
T t
t Tt tt
Male
Gametes
Female Gametes
1/2 tall : 1/2 dwarf
1:1
37. • Similarly, results from a dihybrid situation were also tested by Mendel.
• He crossed yellow round with green wrinkled plants to be symbolized
genotypically as YYRR & yyrr, respectively.
• The F1 hybrid would be YyRr (yellow-round) which when backcrossed to
double recessive yyrr parent will result in four phenotypes in equal
number, i.e.,
Yellow- round (YyRr); yellow wrinkled (Yyrr);
green round (yyRr); green wrinkled (yyrr)
(Dihybrid test cross ratio 1:1:1:1).
37
39. 39
F1 x green wrinkled parent F1 x green wrinkled Parent
YyRr yyrr
Gametes YR, Yr, yR, yr yr
Male
Gametes
Female Gametes
Yellow- round (YyRr): yellow wrinkled (Yyrr): green round (yyRr): green wrinkled (yyrr)
1: 1: 1: 1
YR Yr yR yr
yr YyRr Yyrr
yyRr yyrr
40. This proved that:
1. The factors responsible for character expression are particulate in
nature.
2. Segregation of factors takes place which shows that they do not blend
with one another.
3. Grouping or the assortment of the factors is random during the process
of gamete formation.
4. 1/4: 1/4 : 1/4 : 1/4 test cross ratio proves that all types of gametes were
produced in equal number and that they had an equal chance for union
amongst themselves.
40
41. Blending Theory
• Before Mendel’s work on hybridization was duly recognized, the
“Blending theory” enjoyed popular support as the basis of
inheritance of characters in living organisms.
• According to this theory, heredity determinants were fluid like which
would always produce a blended expression of the characters of the
two mating individuals.
• For instance, if one parent has black body color and the other white,
their offsprings must be all grey, which cannot be separated again in
black and white in the progeny.
41
43. Particulate Theory
• Mendel contradicted the above idea by showing from his
experimental evidence that the determiners of heredity are individual
particles, which, in various combinations, can produce numerous
shades of expression of a character and that these determinants are
separable unaltered at the time the individual forms gamete.
• This theory is called the particulate theory of inheritance and is now
accepted as valid.
43
44. Resume of Mendel’s Experiments on Pea
Mendel made experiments on the pea using seven different contrasting
characters. He selected pea plant as his experimental material because
of the following advantages that the pea plant offered him:
1. Crossing was easy.
2. The characters were easily distinguishable.
3. The hybrids were fertile and easily mutually crossable
4. Due to special floral structure, contamination from foreign source
was avoided.
5. Their culture was easy.
44
45. Conclusions:
1. Characters are controlled by hereditary determiners (Genes).
2. These determiners (genes) can be dominant or recessive.
3. The genes segregate at the time of gamete formation (do not get
blended).
4. All possible combinations of genes occur in the gametes
(Independent assortment).
5. The gametes combine at random to produce off springs showing all
possible combinations of character.
45
46. Reasons for Mendel’s Success
1. His choice of the pea plant was excellent
2. Mendel started with simple experiments involving only one
character difference and then proceeded with more complicated
ones involving more than one character, making careful analysis of
his data and testing his theoretical expectations.
46
47. 3. He made use of mathematics to explain the biological behavior of
the factors determining character expression.
4. He was lucky that the characters he studied were not linked,
otherwise he might have had difficulty in explaining the character
variation not conforming with his hypotheses, as he had no
knowledge of genes being located on the chromosomes.
47
48. Reasons for Slow Acceptance of Mendel’s Work
1. Some well-known scientists would have no confidence in Mendel’s
interpretation of the basis of inheritance, since they did not think
Mendel was qualified enough to do that.
2. The results of some of the other scientists (Nagli’s work on
Hieracium) were not in conformity with those of Mendel
3. Mendel used mathematics to explain his results, whereas other
scientists did not use this type of approach in the study of biological
material.
4. Mendel was a kind of genius and a little ahead of his time. His
contemporaries were ill equipped to understand him.
48
49. Intermediate dominance
• In our previous discussion on Mendelian inheritance, we observed
that in the F1, one form of the character was dominant over the other.
• During later investigations, this generalization did not hold good
showing expression intermediate between the two parents were
observed.
• Where dominance exists, a single dose of the dominant gene produce
same effect as a double dose, but in case the dominance is
incomplete the two alleles in the hybrid conditions (F1) interact
expression more or less intermediate between the two origin the
character.
49
50. • In a cross between red-flowered (RR) and white (rr) snapdragons, the
flower colour of F1 (Rr) is pink, i.e., between red and white.
• This seems a sort of blending between the original colours.
50
54. • When the F2 was grown, segregation occurred in the usual proportion
of 1/4 red RR; 1/2 pink Rr; 1/4 white rr actually a modification of the
monohybrid phenotypic ratio (shows that gene (R) alone is not
sufficient to produce red but the intensity of the red color is reduced
to pink when allelic constitution is (Rr).
• The segregation of the original colors showed that the heredity
material did not blend in F1.
54
56. A backcross between
• Pink (Rr) and Red (RR) produced 1/2 red and 1/2 pink and
• Pink (Rr) and White (rr) will produce 1/2 pink and 1/2 white.
This shows that the characters are controlled by the particulate
substances which segregate from one another uncontaminated.
56
58. • Take another example: Some varieties of snapdragons have broad
leaves; others have narrow leaves.
• In a cross between broad (BB) and narrow (bb) leaved varieties the F1
(Bb) has intermediate leaves.
58
59. We may write the cross as follows:
Parents Broad Leaves x Narrow Leaves
BB bb
Gametes B b
F1 Bb (Intermediate Leaves)
59
60. • In F2 a segregation of
1 broad (BB): 2 intermediate (Bb) : 1 narrow leaved plants
60
61. 61
F1 x F1 Bb x Bb (Intermediate Leaves)
Gametes B, b B, b
Male
Gametes
Female Gametes
1 broad (BB): 2 intermediate (Bb) : 1 narrow plants
B b
B BB Bb
b Bb bb
62. • When flower colour and leaf shape together i.e., the variety with red
flower and broad leaves (RRBB) crossed with the white flower and the
narrow leaf variety (rrbb); the F1 had pink flowers and intermediate
leaves.
62
63. We may write the cross as follows:
Parents Red Flower Broad Leaves x White Flower and Narrow Leaves
RRBB rrbb
Gametes RB rb
F1 RrBb (Pink Flower Intermediate Leaves)
63
64. • The F2 segregated into 9 distinct phenotypes as follows:
• 1 RRBB red broad :2 RrBB pink broad :2 RRBa red intermediate:
4 RrBb pink intermediate : 1 RRbb red narrow : 2 Rrbb pink narrow:
1 rrBB white broad : 2 rrBb white intermediate : 1 rrbb white narrow
• Each phenotype corresponds to a genotype.
• Here 9:3:3:1 are modified to 1:2:1:2:4:2:1:2:1.
64
65. RRBB RRBb RrBB RrBb
RRBb RRbb RrBb Rrbb
RrBB RrBb rrBB rrBb
RrBb Rrbb rrBb rrbb
RB Rb rB rb
RB
Rb
rB
rb
F1 RrBb
Gametes RB, Rb, rB, rb
Male Gametes
Female
Gametes
65
1 RRBB red broad :2 RrBB pink broad :2 RRBa red intermediate: 4 RrBb pink intermediate : 1 RRbb red
narrow : 2 Rrbb pink narrow: 1rrBB white broad : 2 rrBb white intermediate : 1 rrbb white narrow
9:3:3:1 are modified to 1:2:1:2:4:2:1:2:1.
F2
66. Physical Basis of Mendelian Inheritance
• Mendel had no knowledge of the existence of chromosomes.
• The rediscovery of Mendel’s work, attributing inheritance of
characters to particulate factors (now called genes) inspired scientists
to explain the nature of these factors.
66
67. They argued that in order to be heredity determiners these particulate
factors must possess the following attributes:
1. They should be continuous from one cell division to another.
2. They should be present in pairs in diploid organism and separate
out into different gametes at the time of gamete formation
(segregation).
3. Each should have its own individuality and differ qualitatively from
the other.
4. They should be capable of random reunion at the fertilization
process.
67
68. • In 1902 Sutton and Boveri put forth the Chromosomes Theory of
Heredity which correctly answered the above questions.
• According to Sutton-Boveri hypothesis, genes (determiners) are
present on the chromosomes in a linear order.
• The chromosomes exist in pairs in the diploid organism (2n) and in
the haploid organism the chromosome number is reduced to one half
the original number (n) (Mendel’s law of segregation).
• Members of homologous pairs of chromosomes separate or
segregate from each other during meiosis; their diploid number is
restored at fertilization.
68
69. • Two chromosomes carrying different genes assort independently of
their original mates (homologues) depending upon the way they
reorient themselves on the metaphase or equatorial plate (Mendel’s
independent assortment).
• It is just a chance that the paternal and the maternal sets may go in
original combination or may form new combinations.
• It will be noted that the behaviour of the chromosomes conforms to
that of the Mendelian factors (genes) and are, therefore, the physical
basis of heredity.
• There is a close parallelism between the two things, genes and the
chromosomes.
69