This document discusses multiple chromosome interchanges and their use in plant breeding. It begins by defining interchanges as structural changes where non-homologous chromosome segments are exchanged. Interchanges can cause changes in linkage and chromosome behavior. The document then provides examples of naturally occurring interchanges in various plant species like Oenothera lamarckiana. It describes how interchanges can lead to semisterility and discusses different gamete types produced. It focuses on complex interchange systems in Oenothera that maintain permanent hybridity through mechanisms like balanced lethals and gametic lethals. The document concludes by outlining Burnham's method for using multiple interchanges to produce homozygous inbred lines through gamete selection.
This document discusses balanced lethal systems in organisms. It provides examples of balanced lethal systems in Drosophila involving the curly and plum genes, and in Oenothera plants. In Oenothera, there are two types of balanced lethal mechanisms - one involving gametic lethality and the other involving zygotic lethality. The balanced lethal systems ensure that only heterozygotes survive by eliminating homozygotes for lethal alleles.
Chromosomal aberrations, utilization of aneuploids, chimeras and role of allo...GauravRajSinhVaghela
This document provides information about chromosomal aberrations. It begins by defining chromosomes and chromosomal aberrations. There are two main types of chromosomal aberrations: structural and numerical. Structural aberrations include deletions, duplications, inversions, and translocations which alter chromosome structure but not number. Specific structural aberrations like deletions are then defined and examples of diseases caused by deletions are provided. The document also discusses duplication, inversion and provides examples.
GENETICS
CYTOGENETICS
Definition of Linkage, Coupling and Repulsion hypothesis, Linkage group- Drosophila, maize and man, Types of linkage-complete linkage and incomplete linkage, Factors affecting linkage- distance between genes, age, temperature, radiation, sex, chemicals and nutrition, Significance of linkage.
The tendency of two or more genes to stay together (i.e., the co-existence of two or more genes) in the same chromosome during inheritance is known as LINKAGE. The linked genes are present on the same chromosome are said to be SYNTENIC. The linked genes do not show independent assortment.
LINKAGE v/s INDEPENDENT ASSORTMENT
The frequency of linkage or the strength recombination is influenced by several factors (agents).
Charles Darwin observed that crossed plants of Linaria vulgaris were taller and more vigorous than self-fertilized plants of the same species. Heterosis, coined by Shull in 1952, refers to the increased performance of F1 hybrid plants compared to the average of their inbred parental lines, in traits like biomass, size, yield and resistance. There are several hypotheses for heterosis, including dominance, overdominance and epistasis models. The dominance model proposes that superior performance is due to dominant alleles masking recessive alleles, while the overdominance model suggests heterozygosity itself provides benefits over either homozygote.
Gene pyramiding involves combining multiple genes from different parents to develop elite varieties with improved traits. Marker assisted selection can facilitate gene pyramiding by allowing breeders to select plants with desired gene combinations at an early stage. The document discusses strategies for gene pyramiding such as iterative hybridization and co-transformation, and how molecular markers can aid in selecting plants with target genes and pyramiding genes into a single variety more effectively.
22. Polyploidy in plant breeding in crop improvementNaveen Kumar
Polyploidy refers to organisms that have more than two complete sets of chromosomes. It occurs naturally in plants through processes like autopolyploidy, where multiple chromosome sets are from the same species, and allopolyploidy, where chromosome sets are from different species. Polyploidy provides benefits like increased size, vigor and fertility restoration in some cases. It has played an important role in crop evolution, with many important crops being polyploid like potato, banana and coffee. Polyploidy can be artificially induced using techniques like colchicine treatment which inhibits chromosome separation. This has applications in crop improvement through creating new varieties and restoring fertility in interspecific crosses.
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
role of Chromosome variations in crop improvement in cereal cropsSANJAY KUMAR SANADYA
(1) Chromosomal variations such as translocations, inversions, deficiencies, and duplications have been produced in many cereal crops and used to develop genetic maps, locate genes, and manipulate breeding.
(2) Techniques like haploid breeding, synthetic polyploids, and alien introgression have also been used to develop improved crop varieties with new traits.
(3) Advances in chromosome banding and fluorescence in situ hybridization (FISH) have provided tools to precisely characterize karyotypes and detect introgressed alien segments for crop improvement.
This document discusses balanced lethal systems in organisms. It provides examples of balanced lethal systems in Drosophila involving the curly and plum genes, and in Oenothera plants. In Oenothera, there are two types of balanced lethal mechanisms - one involving gametic lethality and the other involving zygotic lethality. The balanced lethal systems ensure that only heterozygotes survive by eliminating homozygotes for lethal alleles.
Chromosomal aberrations, utilization of aneuploids, chimeras and role of allo...GauravRajSinhVaghela
This document provides information about chromosomal aberrations. It begins by defining chromosomes and chromosomal aberrations. There are two main types of chromosomal aberrations: structural and numerical. Structural aberrations include deletions, duplications, inversions, and translocations which alter chromosome structure but not number. Specific structural aberrations like deletions are then defined and examples of diseases caused by deletions are provided. The document also discusses duplication, inversion and provides examples.
GENETICS
CYTOGENETICS
Definition of Linkage, Coupling and Repulsion hypothesis, Linkage group- Drosophila, maize and man, Types of linkage-complete linkage and incomplete linkage, Factors affecting linkage- distance between genes, age, temperature, radiation, sex, chemicals and nutrition, Significance of linkage.
The tendency of two or more genes to stay together (i.e., the co-existence of two or more genes) in the same chromosome during inheritance is known as LINKAGE. The linked genes are present on the same chromosome are said to be SYNTENIC. The linked genes do not show independent assortment.
LINKAGE v/s INDEPENDENT ASSORTMENT
The frequency of linkage or the strength recombination is influenced by several factors (agents).
Charles Darwin observed that crossed plants of Linaria vulgaris were taller and more vigorous than self-fertilized plants of the same species. Heterosis, coined by Shull in 1952, refers to the increased performance of F1 hybrid plants compared to the average of their inbred parental lines, in traits like biomass, size, yield and resistance. There are several hypotheses for heterosis, including dominance, overdominance and epistasis models. The dominance model proposes that superior performance is due to dominant alleles masking recessive alleles, while the overdominance model suggests heterozygosity itself provides benefits over either homozygote.
Gene pyramiding involves combining multiple genes from different parents to develop elite varieties with improved traits. Marker assisted selection can facilitate gene pyramiding by allowing breeders to select plants with desired gene combinations at an early stage. The document discusses strategies for gene pyramiding such as iterative hybridization and co-transformation, and how molecular markers can aid in selecting plants with target genes and pyramiding genes into a single variety more effectively.
22. Polyploidy in plant breeding in crop improvementNaveen Kumar
Polyploidy refers to organisms that have more than two complete sets of chromosomes. It occurs naturally in plants through processes like autopolyploidy, where multiple chromosome sets are from the same species, and allopolyploidy, where chromosome sets are from different species. Polyploidy provides benefits like increased size, vigor and fertility restoration in some cases. It has played an important role in crop evolution, with many important crops being polyploid like potato, banana and coffee. Polyploidy can be artificially induced using techniques like colchicine treatment which inhibits chromosome separation. This has applications in crop improvement through creating new varieties and restoring fertility in interspecific crosses.
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
role of Chromosome variations in crop improvement in cereal cropsSANJAY KUMAR SANADYA
(1) Chromosomal variations such as translocations, inversions, deficiencies, and duplications have been produced in many cereal crops and used to develop genetic maps, locate genes, and manipulate breeding.
(2) Techniques like haploid breeding, synthetic polyploids, and alien introgression have also been used to develop improved crop varieties with new traits.
(3) Advances in chromosome banding and fluorescence in situ hybridization (FISH) have provided tools to precisely characterize karyotypes and detect introgressed alien segments for crop improvement.
Basics of Undergraduate/university fellows
Epistasis is a Greek word that means standing over.
BATESON used term epistasis to describe the masking effect in 1909
The term epistasis describes a certain relationship between genes, where an allele of
one gene hides or masks the visible output or phenotype of another gene.
When two different genes which are not alleles, both affect the same character in such
a way that the expression of one masks (inhibits or suppresses) the expression of the
other gene, the phenomenon is said to be epistasis.
The gene that suppresses other gene expression is known as Epistatic gene.
The gene that is suppressed or remain obscure is called Hypostatic gene
The classical phenotypic ratio of 9:3:3:1 F2 ratio becomes modified by epistasis.
This document discusses aneuploidy and polyploidy in plants. It defines aneuploidy as a change in chromosome number involving one or a few chromosomes. There are three main types of aneuploidy: monosomics lacking one chromosome, nullisomics lacking one chromosome pair, and polysomics with an extra chromosome or pair. Polyploidy refers to having more than two sets of chromosomes and includes autopolyploidy from genome doubling within a species and allopolyploidy from interspecific hybridization. Both aneuploidy and polyploidy can be used in plant breeding and crop improvement.
Distant hybridization involves crossing individuals from different plant species or genera. It has been used to transfer desirable traits like disease resistance between crops. Some key challenges include hybrid sterility and incompatible crosses due to genetic differences between parental species. Techniques like embryo rescue and colchicine treatment have helped produce new crops through wide crosses, such as Nerica rice and triticale wheat-rye hybrids. Distant hybridization remains limited by barriers like hybrid breakdown but has achieved successes in improving crop varieties.
Multiple inbred founder lines are inter-mated for several generations prior to creating inbred lines, resulting in a diverse population whose genomes are fine scale mosaics of contributions from all founders.
This document summarizes a seminar on the molecular basis of heterosis, or hybrid vigor, in crop plants. It discusses the history of research on heterosis dating back to Darwin. Modern research shows that heterozygous hybrids often outperform their homozygous parents in traits like yield, growth, and stress resistance. Several genetic models have been proposed to explain heterosis, including dominance, overdominance, and epistasis, but no single model is sufficient. Omics studies of hybrids and polyploids have found both additive and non-additive changes in gene expression, proteins, and metabolites involved in growth, development, stress response, and signaling pathways.
This document discusses clean gene technology for developing transgenic plants without selectable marker genes. It presents 5 methods for producing marker-free transgenic plants: 1) co-transformation, 2) site-specific recombination-mediated marker deletion using the Cre/loxP system, 3) transposon-based marker methods, 4) intrachromosomal recombination, and 5) removal of chloroplast marker genes using homologous recombination. Each method is described briefly along with their advantages and limitations. The document concludes with a list of references on clean gene technology and selectable marker genes.
Transgressive segregation occurs when hybrid offspring exhibit extreme phenotypes that are more exaggerated than those observed in the parental lines. It is caused by quantitative inheritance involving multiple genes interacting in new combinations. Hybrids may display traits beyond the parental range due to recombination of alleles, increased mutation rates, or epistatic effects between loci. Transgressive segregation introduces novel variation and is most common when distantly related lineages are crossed.
This document discusses the C-Value Paradox, which is the observation that there is no correlation between the complexity of an organism and the amount of DNA (C-value) in its genome. The document provides examples showing that C-values, or the amount of DNA per haploid cell, can vary widely both within and across species, from 105 base pairs in mycoplasma to over 109 base pairs in mammals. While complexity tends to increase with higher C-values, exceptions exist, demonstrating there is no direct linear relationship between genome size and organism complexity. The term "C-value" refers to the haploid DNA content of a species.
This document discusses plant introduction as a method of plant breeding. It begins by defining plant introduction as transferring plant genotypes or groups of genotypes to new areas where they have not been previously grown. The document then covers the history of plant introduction, the different types of plant introduction, the purposes of plant introduction, agencies involved in plant introduction, and the process of acclimatization. It also discusses the merits and demerits of plant introduction as a plant breeding method.
This document discusses heterosis breeding and the commercial exploitation of hybrids. It defines heterosis as increased vigor and fertility from hybridization between unrelated strains. The genetic bases of heterosis are the dominance and overdominance hypotheses. Heterosis breeding led to the development of different types of crosses, including single crosses, double crosses, three-way crosses, and top crosses, which are used commercially. Hybrids show increased yield, quality, disease resistance, and other advantages over pure lines or open-pollinated varieties.
Double haploids are produced by doubling the chromosomes of haploid cells. Haploid cells have half the number of chromosomes as the original organism due to meiosis. A doubled haploid would have the full chromosome number and be homozygous. There are two main methods to produce haploids - anther/pollen culture (androgenesis) and ovary/ovule culture (gynogenesis). The haploids can then be doubled using chemicals like colchicine to produce doubled haploids. Doubled haploids have benefits for plant breeding as they are fully homozygous in the first generation, allowing for faster breeding cycles.
This document summarizes the process of allopolyploidy in crop species evolution. It discusses how allopolyploids contain chromosomes from two or more different species and can occur naturally or be experimentally produced. A key example provided is the origin of Raphanobrassica, an allotetraploid produced by crossing Raphanus sativus (radish) and Brassica oleracea (cabbage). While the initial hybrid was sterile, chromosome doubling resulted in a fertile allotetraploid with 36 chromosomes that exhibited traits of both parent species. The document notes how allopolyploidization has contributed to the evolution of important crop species like wheat, cotton and tobacco.
A general account of Quantitative (Multiple factor or Polygenic) Inheritance; Examples : Kernel colour in Wheat, Ear size (Cob length ) in Maize(Zea mays) ; Differences between Qualitative and Quantitative Inheritance
Wide hybridization is a technique used to transfer agriculturally important traits from alien species to cultivated plants. It allows for greater genetic variability but can be hampered by issues like poor crossability and hybrid sterility. These barriers have been overcome through techniques like the use of growth hormones, improved culture conditions, chromosome doubling, and bridge crosses. Alien addition lines carry one chromosome pair from another species in addition to the parent species' normal chromosomes. They allow for the transfer of traits like disease resistance while limiting the introduction of undesirable genes. Alien addition lines have been developed in several important crop species like wheat and tobacco.
Molecular marker and its application to genome mapping and molecular breedingFOODCROPS
Molecular markers are genetic elements that can be used to follow chromosomes or chromosomal segments during genetic analysis. Molecular markers include molecular techniques like single nucleotide polymorphisms (SNPs) and simple sequence repeats (SSRs). SSRs, also known as microsatellites, are tandem repeats of short DNA motifs that are highly polymorphic due to replication slippage errors. SNPs are single base pair changes that are the most common type of genetic variation. Both SNPs and SSRs are useful molecular markers that can be detected through polymerase chain reaction (PCR) and are important tools for genome mapping and molecular breeding applications.
Linkage refers to the presence of two different genes on the same chromosome . Two genes that occur on the same chromosome are said to be linked, and those that occur very close together are tightly linked.
Genomics and its application in crop improvementKhemlata20
meaning ,definition of genome ,genomics ,tools of genomics ,what is genome sequencing ,methods of genome sequencingand genome mapping ,advantage of genomics over traditional breeding program, examples of some crops whose genome has been sequenced, important points about genomics, work in the field of genomics ,applications of genomics .classification of genomics .different Omics in genomics like Proteomics ,Transcriptomics ,Metabolomics ,Need of genome sequencing
Linkage and crossing over , discovery of linked genes,types of crossing over,significance and difference between linkage and crossing over, complete presentation with suitable examples and figures
Basics of Undergraduate/university fellows
Epistasis is a Greek word that means standing over.
BATESON used term epistasis to describe the masking effect in 1909
The term epistasis describes a certain relationship between genes, where an allele of
one gene hides or masks the visible output or phenotype of another gene.
When two different genes which are not alleles, both affect the same character in such
a way that the expression of one masks (inhibits or suppresses) the expression of the
other gene, the phenomenon is said to be epistasis.
The gene that suppresses other gene expression is known as Epistatic gene.
The gene that is suppressed or remain obscure is called Hypostatic gene
The classical phenotypic ratio of 9:3:3:1 F2 ratio becomes modified by epistasis.
This document discusses aneuploidy and polyploidy in plants. It defines aneuploidy as a change in chromosome number involving one or a few chromosomes. There are three main types of aneuploidy: monosomics lacking one chromosome, nullisomics lacking one chromosome pair, and polysomics with an extra chromosome or pair. Polyploidy refers to having more than two sets of chromosomes and includes autopolyploidy from genome doubling within a species and allopolyploidy from interspecific hybridization. Both aneuploidy and polyploidy can be used in plant breeding and crop improvement.
Distant hybridization involves crossing individuals from different plant species or genera. It has been used to transfer desirable traits like disease resistance between crops. Some key challenges include hybrid sterility and incompatible crosses due to genetic differences between parental species. Techniques like embryo rescue and colchicine treatment have helped produce new crops through wide crosses, such as Nerica rice and triticale wheat-rye hybrids. Distant hybridization remains limited by barriers like hybrid breakdown but has achieved successes in improving crop varieties.
Multiple inbred founder lines are inter-mated for several generations prior to creating inbred lines, resulting in a diverse population whose genomes are fine scale mosaics of contributions from all founders.
This document summarizes a seminar on the molecular basis of heterosis, or hybrid vigor, in crop plants. It discusses the history of research on heterosis dating back to Darwin. Modern research shows that heterozygous hybrids often outperform their homozygous parents in traits like yield, growth, and stress resistance. Several genetic models have been proposed to explain heterosis, including dominance, overdominance, and epistasis, but no single model is sufficient. Omics studies of hybrids and polyploids have found both additive and non-additive changes in gene expression, proteins, and metabolites involved in growth, development, stress response, and signaling pathways.
This document discusses clean gene technology for developing transgenic plants without selectable marker genes. It presents 5 methods for producing marker-free transgenic plants: 1) co-transformation, 2) site-specific recombination-mediated marker deletion using the Cre/loxP system, 3) transposon-based marker methods, 4) intrachromosomal recombination, and 5) removal of chloroplast marker genes using homologous recombination. Each method is described briefly along with their advantages and limitations. The document concludes with a list of references on clean gene technology and selectable marker genes.
Transgressive segregation occurs when hybrid offspring exhibit extreme phenotypes that are more exaggerated than those observed in the parental lines. It is caused by quantitative inheritance involving multiple genes interacting in new combinations. Hybrids may display traits beyond the parental range due to recombination of alleles, increased mutation rates, or epistatic effects between loci. Transgressive segregation introduces novel variation and is most common when distantly related lineages are crossed.
This document discusses the C-Value Paradox, which is the observation that there is no correlation between the complexity of an organism and the amount of DNA (C-value) in its genome. The document provides examples showing that C-values, or the amount of DNA per haploid cell, can vary widely both within and across species, from 105 base pairs in mycoplasma to over 109 base pairs in mammals. While complexity tends to increase with higher C-values, exceptions exist, demonstrating there is no direct linear relationship between genome size and organism complexity. The term "C-value" refers to the haploid DNA content of a species.
This document discusses plant introduction as a method of plant breeding. It begins by defining plant introduction as transferring plant genotypes or groups of genotypes to new areas where they have not been previously grown. The document then covers the history of plant introduction, the different types of plant introduction, the purposes of plant introduction, agencies involved in plant introduction, and the process of acclimatization. It also discusses the merits and demerits of plant introduction as a plant breeding method.
This document discusses heterosis breeding and the commercial exploitation of hybrids. It defines heterosis as increased vigor and fertility from hybridization between unrelated strains. The genetic bases of heterosis are the dominance and overdominance hypotheses. Heterosis breeding led to the development of different types of crosses, including single crosses, double crosses, three-way crosses, and top crosses, which are used commercially. Hybrids show increased yield, quality, disease resistance, and other advantages over pure lines or open-pollinated varieties.
Double haploids are produced by doubling the chromosomes of haploid cells. Haploid cells have half the number of chromosomes as the original organism due to meiosis. A doubled haploid would have the full chromosome number and be homozygous. There are two main methods to produce haploids - anther/pollen culture (androgenesis) and ovary/ovule culture (gynogenesis). The haploids can then be doubled using chemicals like colchicine to produce doubled haploids. Doubled haploids have benefits for plant breeding as they are fully homozygous in the first generation, allowing for faster breeding cycles.
This document summarizes the process of allopolyploidy in crop species evolution. It discusses how allopolyploids contain chromosomes from two or more different species and can occur naturally or be experimentally produced. A key example provided is the origin of Raphanobrassica, an allotetraploid produced by crossing Raphanus sativus (radish) and Brassica oleracea (cabbage). While the initial hybrid was sterile, chromosome doubling resulted in a fertile allotetraploid with 36 chromosomes that exhibited traits of both parent species. The document notes how allopolyploidization has contributed to the evolution of important crop species like wheat, cotton and tobacco.
A general account of Quantitative (Multiple factor or Polygenic) Inheritance; Examples : Kernel colour in Wheat, Ear size (Cob length ) in Maize(Zea mays) ; Differences between Qualitative and Quantitative Inheritance
Wide hybridization is a technique used to transfer agriculturally important traits from alien species to cultivated plants. It allows for greater genetic variability but can be hampered by issues like poor crossability and hybrid sterility. These barriers have been overcome through techniques like the use of growth hormones, improved culture conditions, chromosome doubling, and bridge crosses. Alien addition lines carry one chromosome pair from another species in addition to the parent species' normal chromosomes. They allow for the transfer of traits like disease resistance while limiting the introduction of undesirable genes. Alien addition lines have been developed in several important crop species like wheat and tobacco.
Molecular marker and its application to genome mapping and molecular breedingFOODCROPS
Molecular markers are genetic elements that can be used to follow chromosomes or chromosomal segments during genetic analysis. Molecular markers include molecular techniques like single nucleotide polymorphisms (SNPs) and simple sequence repeats (SSRs). SSRs, also known as microsatellites, are tandem repeats of short DNA motifs that are highly polymorphic due to replication slippage errors. SNPs are single base pair changes that are the most common type of genetic variation. Both SNPs and SSRs are useful molecular markers that can be detected through polymerase chain reaction (PCR) and are important tools for genome mapping and molecular breeding applications.
Linkage refers to the presence of two different genes on the same chromosome . Two genes that occur on the same chromosome are said to be linked, and those that occur very close together are tightly linked.
Genomics and its application in crop improvementKhemlata20
meaning ,definition of genome ,genomics ,tools of genomics ,what is genome sequencing ,methods of genome sequencingand genome mapping ,advantage of genomics over traditional breeding program, examples of some crops whose genome has been sequenced, important points about genomics, work in the field of genomics ,applications of genomics .classification of genomics .different Omics in genomics like Proteomics ,Transcriptomics ,Metabolomics ,Need of genome sequencing
Linkage and crossing over , discovery of linked genes,types of crossing over,significance and difference between linkage and crossing over, complete presentation with suitable examples and figures
Linkage and crossing over are genetic phenomena that occur during meiosis. Linkage refers to genes staying together on the same chromosome through generations without separating. Crossing over involves the exchange of genetic material between homologous chromosomes, resulting in new combinations of genes. It occurs during prophase I of meiosis and leads to variability that is important for evolution. Both linkage and crossing over are significant for inheritance and breeding.
1. Linkage occurs when genes located on the same chromosome fail to assort independently during meiosis. This causes traits to be inherited together in offspring.
2. Bateson and Punnett first reported linkage in 1906 while studying flower color and pollen shape in peas. They observed a deviation from expected Mendelian ratios, indicating linkage between the genes.
3. Morgan's studies of fruit flies provided the first evidence that linkage is due to genes being located on the same chromosome. Crossing over during meiosis can lead to new combinations of linked genes.
Chromosomal and gene mutations can both cause changes to an organism's genetic code. Chromosomal mutations, also called genome mutations, involve changes to the structure or number of chromosomes, such as deletions, duplications, inversions, or changes in ploidy. Gene mutations involve changes to the DNA sequence of individual genes, such as point mutations, frameshift mutations, or mutations that change the resulting protein. Both types of mutations can be spontaneous or induced, and can have effects ranging from silent to lethal depending on the genes and chromosomes involved.
This document discusses genetic linkage and crossing over. It explains that genes located close together on the same chromosome are linked and tend to be inherited together, while genes on different chromosomes assort independently. Crossing over occurs when homologous chromosomes exchange segments during meiosis, resulting in new combinations of linked genes and the production of both parental and recombinant gametes. The frequency of crossing over between two genes decreases as they are located closer together on a chromosome.
This document summarizes key concepts related to chromosomes and chromosomal aberrations. It defines chromosomes as structures carrying genetic information in cells. Chromosomal aberrations refer to structural or numerical changes in chromosomes. Structural changes include deletions, duplications, inversions, and translocations that alter chromosome structure. Numerical changes include aneuploidy, where the number of individual chromosomes changes, and euploidy, where full sets of chromosomes are added or removed. Specific examples of structural and numerical aberrations in humans that cause genetic diseases are provided. The roles of chromosomal aberrations in evolution and crop improvement are also briefly discussed.
Linkage and Crossing over (Sanjay Chetry).pptxsanjaychetry2
Linkage
1. Linkage ensures to keep the genes in a chromosome to inherit together
2. The strength of linkage between two genes is inversely proportional to the distance between them in the chromosome
3. The strength of linkage between two genes increases with the decrease in distance between them.
4. The strength of linkage decrease with increase in distance between the genes.
5. Linkage ensures the maintenance of parental trait in the offspring.
6. Linkage reduces the chance of creation of variability with sexual reproduction.
Crossing Over
1. Crossing over facilitates the separation of genes present chromosome and segregate into different gametes.
2. The chance of crossing over between two genes is directly proportional to the distance between them in the chromosome
3. The chance of crossing over between two genes decreases with the decrease in the distance between them.
4. The chance of crossing increases with increase in distance between the genes.
5. The crossing over causes alterations in the parental traits in the offspring.
6. Crossing over increases the chance of variability with sexual reproduction.
Crop improvement can be achieved through both sexual and asexual reproduction. Sexual reproduction combines genes from two parents, creating new combinations, while asexual reproduction clones the parent plant. Vegetative propagation methods include cuttings, grafting, and tissue culture. Genetic engineering allows for direct transfer of genes between organisms. Traditional breeding techniques also improve crops through selection of desirable traits over generations. [/SUMMARY]
Body cells and gametes have different chromosome numbers and structures. Body cells are diploid with 46 chromosomes, while gametes are haploid with 23 chromosomes. Meiosis produces haploid gametes from diploid body cells, reducing the chromosome number and creating genetic variation through independent assortment and crossing over. Gregor Mendel's experiments with pea plants established the laws of inheritance and provided the foundation for genetics.
1. Morgan's experiments with Drosophila showed that genes located close together on the same chromosome (linked genes) tend to be inherited together more often than expected by Mendel's law of independent assortment.
2. Crossing over during meiosis can lead to new combinations of linked genes, with the frequency of crossing over determining how far apart genes are on the genetic map.
3. Sturtevant used recombination frequencies between traits to construct the first genetic map, with map units called centimorgans representing a 1% chance of crossing over.
Introduction, Types-somatic and germinal; Mechanism of meiotic crossing oversynapsis, duplication of chromosomes, breakage and union, terminalization;
Cytological basis of crossing over - Stern’s experiment in Drosophila; Creighton
and McClintock’s experiment in Maize; Crossing over in Drosophila, Construction
of genetic maps in Drosophila - two point and three-point crosses; Interference and
coincidence.
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 document discusses balanced and unbalanced lethal genes. It provides the example of the yellow mouse, which is lethal when homozygous for the yellow gene due to failure of yellow sperm to penetrate yellow eggs. It then describes balanced lethal systems, where two different recessive lethal genes balance each other's effects to allow survival of heterozygotes. Muller's discovery of the balanced lethal genes beaded and Le in Drosophila is described. The document also discusses chromosome complexes in Oenothera lamarckiana, where the alpha and beta gametic complexes lead to gametic lethality, while complexes gaudens and velans show zygotic lethality.
Crop improvement methods aim to preserve desirable traits and introduce new beneficial traits. Sexual reproduction combines genes from parents, but asexual reproduction clones parents. Inbreeding can preserve traits but causes inbreeding depression. Hybrids between inbred lines show hybrid vigor. Mutations occasionally produce new single gene traits that can be propagated. Selection over generations improves polygenic traits. Creating polyploids like tetraploids sometimes increases size and health. Interspecific hybrids combine traits, with some becoming fertile tetraploids.
Genetic variation arises from four main sources: mutations, sexual reproduction, fertilization, and environmental influences. Mutations are changes in DNA that create new alleles and variations. Sexual reproduction and meiosis increase variation through independent assortment, crossing over, and random fertilization. A dihybrid cross examines inheritance of two traits controlled by separate genes. Mendel's dihybrid crosses on peas produced offspring in a 9:3:3:1 ratio, showing traits assort independently. Genetic variation allows populations to adapt to environmental changes over generations.
This document discusses various types of chromosomal mutations and aberrations. It describes two main types - changes in chromosome structure, which includes deletions, duplications, inversions, and translocations, and changes in chromosome number, such as aneuploidy (gaining or losing a chromosome) and euploidy (gaining or losing a full set of chromosomes). Specific examples of each type of structural change and number change are provided, along with their genetic effects and examples in humans and other organisms.
A Visual Guide to 1 Samuel | A Tale of Two HeartsSteve Thomason
These slides walk through the story of 1 Samuel. Samuel is the last judge of Israel. The people reject God and want a king. Saul is anointed as the first king, but he is not a good king. David, the shepherd boy is anointed and Saul is envious of him. David shows honor while Saul continues to self destruct.
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptxEduSkills OECD
Iván Bornacelly, Policy Analyst at the OECD Centre for Skills, OECD, presents at the webinar 'Tackling job market gaps with a skills-first approach' on 12 June 2024
Chapter wise All Notes of First year Basic Civil Engineering.pptxDenish Jangid
Chapter wise All Notes of First year Basic Civil Engineering
Syllabus
Chapter-1
Introduction to objective, scope and outcome the subject
Chapter 2
Introduction: Scope and Specialization of Civil Engineering, Role of civil Engineer in Society, Impact of infrastructural development on economy of country.
Chapter 3
Surveying: Object Principles & Types of Surveying; Site Plans, Plans & Maps; Scales & Unit of different Measurements.
Linear Measurements: Instruments used. Linear Measurement by Tape, Ranging out Survey Lines and overcoming Obstructions; Measurements on sloping ground; Tape corrections, conventional symbols. Angular Measurements: Instruments used; Introduction to Compass Surveying, Bearings and Longitude & Latitude of a Line, Introduction to total station.
Levelling: Instrument used Object of levelling, Methods of levelling in brief, and Contour maps.
Chapter 4
Buildings: Selection of site for Buildings, Layout of Building Plan, Types of buildings, Plinth area, carpet area, floor space index, Introduction to building byelaws, concept of sun light & ventilation. Components of Buildings & their functions, Basic concept of R.C.C., Introduction to types of foundation
Chapter 5
Transportation: Introduction to Transportation Engineering; Traffic and Road Safety: Types and Characteristics of Various Modes of Transportation; Various Road Traffic Signs, Causes of Accidents and Road Safety Measures.
Chapter 6
Environmental Engineering: Environmental Pollution, Environmental Acts and Regulations, Functional Concepts of Ecology, Basics of Species, Biodiversity, Ecosystem, Hydrological Cycle; Chemical Cycles: Carbon, Nitrogen & Phosphorus; Energy Flow in Ecosystems.
Water Pollution: Water Quality standards, Introduction to Treatment & Disposal of Waste Water. Reuse and Saving of Water, Rain Water Harvesting. Solid Waste Management: Classification of Solid Waste, Collection, Transportation and Disposal of Solid. Recycling of Solid Waste: Energy Recovery, Sanitary Landfill, On-Site Sanitation. Air & Noise Pollution: Primary and Secondary air pollutants, Harmful effects of Air Pollution, Control of Air Pollution. . Noise Pollution Harmful Effects of noise pollution, control of noise pollution, Global warming & Climate Change, Ozone depletion, Greenhouse effect
Text Books:
1. Palancharmy, Basic Civil Engineering, McGraw Hill publishers.
2. Satheesh Gopi, Basic Civil Engineering, Pearson Publishers.
3. Ketki Rangwala Dalal, Essentials of Civil Engineering, Charotar Publishing House.
4. BCP, Surveying volume 1
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
This document provides an overview of wound healing, its functions, stages, mechanisms, factors affecting it, and complications.
A wound is a break in the integrity of the skin or tissues, which may be associated with disruption of the structure and function.
Healing is the body’s response to injury in an attempt to restore normal structure and functions.
Healing can occur in two ways: Regeneration and Repair
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Complications of wound healing like infection, hyperpigmentation of scar, contractures, and keloid formation.
1. MULTIPLE INTERCHANGES
THEIR USE IN PRODUCING INBREDS, LINKED MARKER METHODS AND
TRANSFER OF GENES
SUBMITTED BY:
CHAVAN SONAL
PhD first year
RAD/2020-24
Dept. of Genetics and Plant Breeding
Professor Jayashankar Telangana State Agricultural University (PJTSAU)
Course Title: Cellular and Chromosomal Manipulations in Crop Improvement (GP-604)
2. INTERCHANGES
• Interchanges are those structural
changes in chromosomes, where
terminal segments of non-
homologous chromosomes have
exchanged positions.
• These changes are also called
reciprocal translocations.
• Interchanges also bring about changes
in linkage relationships and lead to
changes in chromosome structure and
behaviour.
3. Occurrence of Interchanges
• Belling for the first time found semisterility in hybrid plants of Stizolobium
deeringianum, obtained due to intraspecific hybridization.
• Semisterility was manifest by 50% pollen sterility and 50% seed set.
• In the progeny of hybrid plants showing semisterilty, 50% individuals were
semisterile and 50% were fertile.
• Blakeslee on Datura stramonium, explained semisterility in Stizolobium on the
basis of ‘segmental interchanges’ between non-homologues.
• Rings of four chromosomes in meiosis were observed in Datura and were
associated with semisterility.
• Example of naturally occurring interchanges was available in Oenothera
lamarckiana. These were complex interchanges.
• Later recorded in Tradescantia and Rhoeo discolor also.
4. • Interchanges in plants are usually associated with semisterility of gametes.
There can be plants which have same
interchange in both sets of chromosomes,
called as interchange homozygotes and
would exhibit complete fertility.
Semisterility is observed only in those
plants which have translocations in only one
set of chromosomes, the other set being
normal. These plants are called Interchange
heterozygotes.
7. Selfing of Translocation heterozygote
• When an interchange heterozygote is
selfed, it yields normal, interchange
heterozygote and interchange
homozygote in 1:2:1 ratio, suggesting
that under ordinary situation,
translocation heterozygosity is not a
stable feature.
• The genus Oenothera, and to a lesser
extent other genera of Onagraceae,
like Gaura and Clarkia are some
examples where mechanisms have
been evolved to maintain permanent
hybridity.
8. Oenothera
• Hugo de vries in 1901
• Isolated some new
distinct true breeding
types of Oenothera.
• 1920’s, Cleland observed
in Euoenothera the
chain or ring of
chromosomes instead of
normal bivalent
formation.
9. Multiple interchanges
• Interchanges may involve more
than two non-homologous
chromosomes producing rings of 6
or more chromosomes in the
heterozygotes.
• In case of three non-homologous
chromosomes are involved, a ring
of six chromosomes will be
produced
• While a ring of eight chromosomes
would result if four non-
homologous chromosomes were
involved.
10. Oenothera
• In most of the Oenothera races,
two to all of the seven non-
homologous chromosomes are
involved in interchanges.
• In Oenothera lamarckiana, six
non-homologous chromosomes
are involved in reciprocal
translocations producing a ring
of 12 and one bivalent at MI.
11. Chromosome behaviour at meiosis
• Euoenothera -2n=14 with median centromeres and with very little
difference in chromosome size.
• They all are self compatible and capable of self fertilization, although
some of them may be often cross pollinated.
• The chromosomes associate in multiple chain or ring configurations.
• Whenever complex rings are formed at anaphase I, adjacent chromosomes
regularly passed to opposite poles.
• That the complex ring formation may be attributed to interchange
heterozygosity was suggested first by Belling.
12.
13. Translocations, which are maintained permanently in heterozygous stage,
keep their genes tightly linked, though located on non-homologous
chromosomes by pairing of homologous segments located on non-homologous
chromosomes.
Genes lying close to a centromere will not only be linked to each other (due to
lack of crossing over between the genes and centromere), but will also be linked
to other genes lying close to centromere of the other non-homologous
chromosome involved in translocation.
This device becomes rather important in plants like Oenothera, where all
chromosomes are involved in a ring and genes located on different
chromosomes, but close to centromeres, are linked together, this thus leads to
two gene complexes or linkage groups, one with translocated chromosomes and
the other with normal chromosomes.
14. Multiple interchanges
• The above device of maintaining, not
only interchromosomal linkage, but also
permanent hybridity, would be
successful only when the chromosomes
of concerned organism have the
following features:
1. Centromeres must be median or
submedian in position
2. Chiasma formation should be confined
to chromosome ends, so that the ring
configurations are flexible and can
easily assume a zig-zag shape which
would result in alternate disjunction.
15. Belling’s Interchange hypothesis
• Applied to complex rings of Oenothera
• The associated ends of adjacent chromosomes are homologous.
• Two ends of a particular chromosome are thus homologous to the ends of
two different chromosomes.
• The rings of chromosomes orient themselves at metaphase I in a zigzag
manner so that only alternate chromosomes go to same pole.
• This alternate disjunction led to reduction in sterility and its combination
with balanced lethal system, gave rise to successful permanent hybrids.
16. Breeding behaviour- Renner complexes
• Permanent hybrids forming rings and
undergoing alternate disjunction form only two
types of functional gametes.
• These results were explained by assuming
presence of two gene complexes in each race,
associated with two types of functional gametes
formed due to alternate disjunction.
• Each gene complex segregates as a whole at
meiosis and passes on to one gamete.
• Each complex is given a specific name and they
are collectively called Renner complexes.
• In Oenothera lamarckiana, complexes are
gaudens and velans.
• These gene complexes
differ in different races.
• Some of these
complexes are lethal in
either of the α (alpha)
and β (beta) gametes,
others are lethal when
homozygous in zygotes.
17.
18. Gaudens and Velans
In Oenothera a ring of twelve and a bivalent is produced.
Alternate segregation results in the viable gametes and has the same
seven chromosomes in all the gametes. i.e. the seven chromosomes form
one linkage group.
Each set of seven chromosomes inherited as a single unit called-Renner
complex.
Gaudens – Genes for green buds, non punctate stems, broad leaves, Red
flecks on rosette leaves.
Velans – Genes for red buds, punctate stems, narrow leaves, no red flecks
on rosette leaves
Arrangement of chromosomes in Velans set is 1-2, 3-4, 5-8, 7-6, 9-10, 11-
12 and 13-14.
Gaudens set is 1-2, 3-12, 5-6, 7-11, 9-4, 8-14 and 13-10.
Chromosomes with ends 1 and 2 pair and form bivalent. The other pair at
their ends and form a ring of 12 chromosomes
On selfing of G/V gives 1GG: 2GV: 1VV
19. • Oenothera lamarckiana is a heterogametic species in which one haploid set of
chromosomes is not identical with the other.
• Of the seven chromosomes making up each set, only one is common to both;
the remaining six chromosomes of one set represent translocations of the six
remaining chromosomes of the other set
• Hence, in the ordinary diploid form of this species there are thirteen
chromosomes of more or less different homologies, only one of which is
represented in duplicate.
20.
21.
22.
23. Balanced lethals
• First reported by Muller (1917)
in Drosophila
• If dominant alleles of two traits,
each associated with a recessive
lethal effects, are present in
heterozygous repulsion phase,
homozygotes will not survive
and permanent hybridity will be
maintained.
• Similar balanced lethal system
operates in Euoenotheras
24. • In Oenothera lamarckiana, the
lethality is zygotic as in the
balanced lethal systems of
Drosophila and would therefore
lead to 50% ovule abortion or
seed set. It is therefore a wasteful
mechanism.
• In several other species of
Oenothera, therefore more
efficient reproductive mechanism
has been evolved to maintain
permanent hybridity i.e., gametic
lethality.
Gametic lethals
Zygotic lethals
Balanced lethals
25. Gametic lethals
• In Oenothera two gametic complexes
• Α (alpha) present in all functional egg cells and eliminated
in pollen
• Β (beta) present in all functional pollen grains and
eliminated in eggs.
• Elimination is due to failure of development of gametes
containing these respective gametic complexes leading to
50% pollen abortion but a full seed set.
• Only that megaspore functions which carries alpha
complex.
26. • Since alpha complex in the egg always
unites with beta complex in pollen,
plants breed true for heterozygous
condition.
• Thus there are two balanced lethal
mechanisms, one involves zygotic
lethality and the other involving
gametic lethality.
Zygotic Lethals
27. Production of Inbred lines
• Burnham (1946) suggested the use of multiple translocation rings for
estabilishing homozygous lines and called it ‘Oenothera’ method of gamete
selection.
Steps involved :
1. Synthesize a line, in which all chromosomes of a haploid set are linked
together by interchanges. They should have complete alternate disjunction
in heterozygous condition, and have a balanced lethal system.
2. Cross the above complex interchange stock with a source to be used for
gamete selection. Each F1 plant would have a different gamete from the
source, but the same gamete from translocation stock, so that the F1 will
form a ring of all chromosomes at meiosis.
28. Cont…
3. Self the F1 plants and grow F2.
4. F2 plants will consist of plants with multiple interchanges and those with
normal chromosomes. These latter plants will be the Inbred lines.
Burnham (1946) also suggested that homozygous lines from promising
hybrids can be obtained by the above method in only those species which
have a relatively low number of chromosomes and where a relatively high
degree of fertility can be maintained in plants heterozygous for interchanges.
In view of the above he suggested barley to be a suitable material, since it
has n=7 and has high fertility (75%) in an interchange heterozygote.
29. Degree of structural heterozygosity
Lowest degree of heterozygosity- large flowers, often outcrossed- bivalents
or rings due to 1 or 2 interchanges.
eg: O. hookeri, O.grandiflora and O.argillicola
Intermediate degree of translocation heterozygosity- large flowers, open-
pollinated, rings of numerous interchanges.
eg: O.irrigua
Permanent hybridity- self pollinated, small flowers, highly inbred- complex
translocation ring, due to alternate disjunction and balanced lethal system.
eg: O. lamarckiana
30. Origin and evolution of Oenothera races
1. Ancestral populations were outcrossing, heterozygous and polymorphic and
carried characteristics like median centromeres, heterozygous and proximal
segments, etc. which favoured accumulation of translocations.
2. Drastic oscillations of climate helped evolution towards permanent structural
hybridity in a gradual manner.
3. Similar translocations were established due to their adaptive superiority and
isolation of populations.
4. Origin of ring formers is attributed to migration from an original centre
followed by hybridization between races from new and the old habitats.
31. Cont…
Immigrants – O. argillicola, O. grandiflora
Hybrids between immigrants – O. parvifloras
Later migrations included narrow leaved strigosa type race, which on crosses with
‘grandiflora’ like race gave biennis I and biennis II.
The ring forming strigosa and biennis III arose from hybrids between biennis I and
biennis II.
32. Cytogenetics localization of genes using
interchanges
• Linkage between marker genes and semi-sterility (interchange breakpoints)
• Once the association of genes are linkage groups with individual chromosomes
has been established, breakpoints in interchanges can be used as markers for
chromosome mapping of genes.
• This has been most successfully done in maize.
33. Uses of Interchanges
• Induced chromosome interchanges, with great potential for generating and
maintaining specific gene combinations, are usually identified by the presence of
characteristic multivalent associations at metaphase in meiotic I followed by
partial pollen and ovule abortion.
• Along with aneuploids and other structural chromosomal alterations,
chromosomal interchanges served as excellent cytogenetic tools for identification
and mapping of various linkage groups in plants.
• Reciprocal translocations help in better understanding of meiotic chromosome
pairing, chiasma influence and formation of trisomics in a number of plants.
• Multiple translocations, in particular, create structural and numerical chromosome
variations more rapidly than simple ones and thus, can be efficiently utilized for
future crop improvement through mutation breeding programmes.
34.
35. A. roylei is an important species of the genus Allium. Because of its compatibility with A. cepa, it has been used as a
donor of genes imparting resistance against leaf blight and downy mildew to latter (de Vries et al. 1992). It has also
been used as a bridge species to transfer genes from A. fistulosum into A. cepa (Khrustaleva and Kik 1998).
36.
37. Fig. 1 Meiotic stages in control (a, b) and interchange
heterozygotes (T-1, T-2 and T-3) of Hordeum vulgare L. (c–l)
in M1 generation.
a)Diakinesis with normal seven bivalents (n = 7).
b) Normal segregation (7:7) at anaphase-I.
c) Two open ring quadrivalents (one attached to
nucleolus).
d) One open ring and one 8-shaped quadrivalents. e) One
8-shaped ring and one chain quadrivalent.
f) One 8-shaped ring and one chain (attached to nucleolus)
quadrivalent.
g) One open ring and one chain quadrivalent.
h) Lagging chromosomes at anaphase-I.
i)Unequal segregation at anaphase-I.
j, k) Single and double chromatin
bridge formation at anaphase-I.
l) Unequal segregation at anaphase II.
38. Fig. 2 Meiotic stages in T-4 interchange
heterozygote of Hordeum vulgare L. (2n = 2x = 14) in
M1 and M2 generation. a) One open ring
hexavalent with four bivalents,
b) one 8-shaped ring hexavalent and four bivalents,
c) one chain hexavalent with four bivalents,
d) a frying pan shaped hexavalent and four
bivalents,
e) one pentavalent along with four bivalents and a
univalent,
f) One quadrivalent and five bivalents,
g) One open ring quadrivalent with five bivalents,
h) One 8-shaped quadrivalent with five bivalents,
i) one chain quadrivalent with five bivalents,
j) triad formation,
k) micronuclei in tetrad and
l) Fertile (stained) and sterile (unstained) pollens.
39. Plants heterozygous for translocations experience significant pollen abortion primarily due to
orientation behaviour of interchange multiples and their disturbances during separation.
For example, alternate disjunction leads to balanced and fertile gamete formation, whereas
adjacent segregation causes sterile gamete formation due to deficiencies and duplication of
chromosome segments.
The inability of the multivalents to separate properly at anaphase or telophase I/II creates various
irregularities like laggards, bridges, unequal chromosome segregation, micronuclei and others.
Interestingly, multiple interchanges have been found to cause unequal chromosome segregation
more frequently than simple interchanges [2] and hence, could be employed for rapid isolation of
trisomics and tetrasomics.
Laggard chromosomes often fail to reach the opposite poles in time and lead to micronuclei
formation later. Ultimately, more abnormalities accumulate which cause nonviable gametes and plant
fertility reduction.