Principles of Inheritance and Variation in Genetics and Evolution pdf
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The document discusses heredity and genetics, focusing on the mechanisms of inheritance, variation, and key experiments by Gregor Mendel, who is regarded as the father of genetics. It highlights Mendel's laws of inheritance, including dominance, segregation, and independent assortment, as well as concepts like alleles, genes, and mutations. Additionally, it covers the rediscovery of Mendel's work and the significance of genetic mapping and sex determination.
Principles of Inheritance and Variation in Genetics and Evolution pdf
- 1. Heredity It is the transmission of characters, resemblances as well as variation from one generation to the next. All right copy reserved. No part of the material can be produced without prior permission
- 2. Genetics • Genetics deals with: • the mechanism of inheritance by which characters pass from parents to offspring • variation of characters from parents to offsprings and their causes. All right copy reserved. No part of the material can be produced without prior permission
- 3. Gregor John Mendel • Formulated laws of heredity • Is regarded as father of genetics • His choice of subjects and aptitude for hybridization had a significant influence on his later work on inheritance. • He published his findings in 1866 in “ Annual Proceedings of the Natural History Society of Brunn” All right copy reserved. No part of the material can be produced without prior permission
- 4. Inheritance • It is the process by which characters are passed on from parent to progeny. All right copy reserved. No part of the material can be produced without prior permission
- 5. Variation • It is the degree by which progeny differ from their parents. All right copy reserved. No part of the material can be produced without prior permission
- 6. Our ancestors knew about inheritance • They exploited the variations that were naturally present in the wild populations of plants and animals to selectively breed and select for organisms that possessed desirable characters. For example Sahiwal cows in Punjab. All right copy reserved. No part of the material can be produced without prior permission
- 7. Salient features of Mendel’s experiments a. Statistical analysis and mathematical logic were applied to problems in biology. b. His experiments had a large sample size. c. He conducted artificial pollination experiments using several true-breeding pea lines. d. Mendel investigated characters in the garden pea plant that were manifested as two opposing traits. All right copy reserved. No part of the material can be produced without prior permission
- 8. Mendel selected pea plant ( Pisum sativum ) • It is a self fertilizing plant because of presence of closed flowers. • Large number of seeds are produced. • It is an annual plant. • In the garden pea plant characters are manifested as two opposing traits. • Artificial cross-pollination could be easily achieved. All right copy reserved. No part of the material can be produced without prior permission
- 9. True / pure breeding lines • A true breeding line is one that, having undergone continuous self-pollination, shows the stable trait inheritance and expression for several generations. All right copy reserved. No part of the material can be produced without prior permission
- 10. Contrasting characters studied by Mendel • stem height – tall / dwarf • flower colour – violet / white • flower position – axial / terminal • pod shape – inflated / constricted • pod colour – green / yellow • seed shape – round / wrinkled • seed colour – yellow / green All right copy reserved. No part of the material can be produced without prior permission
- 11. Monohybrid cross • A breeding experiment dealing with a single character is called monohybrid cross. All right copy reserved. No part of the material can be produced without prior permission
- 12. Monohybrid cross • Crossing tall and dwarf pea plants • Collection of the seeds produced as a result of this cross • Growing them to generate plants of the first hybrid generation called F1 generation. • All the F1 progeny plants are tall. • Self-pollination of the tall F1 plants • In the F2 generation, 3/4th of the F2 plants are tall and 1/4th of the F2 plants are dwarf. All right copy reserved. No part of the material can be produced without prior permission
- 13. Genes • Units of inheritance and contain information that is required to express a particular trait. All right copy reserved. No part of the material can be produced without prior permission
- 14. Alleles • Alleles are slightly different forms of a gene. These code for a pair of contrasting characters. All right copy reserved. No part of the material can be produced without prior permission
- 15. Homozygous • In a true breeding, the allelic pair of genes are identical. All right copy reserved. No part of the material can be produced without prior permission
- 16. Heterozygous • In a heterozygous individual, a pair of dissimilar factors is present. All right copy reserved. No part of the material can be produced without prior permission
- 17. Test cross • An organism showing a dominant phenotype ( and whose genotype is to be determined ) is crossed with the recessive parent. If all progenies show dominant trait, the unknown plant is homozygous and if both dominant and recessive characters are observed, the unknown plant is heterozygous. All right copy reserved. No part of the material can be produced without prior permission
- 18. Mendel’s laws of dominance • In a monohybrid cross, in the F1 generation only one of the parental characters is expressed. All right copy reserved. No part of the material can be produced without prior permission
- 19. Mendel’s law of segregation • During gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors. All right copy reserved. No part of the material can be produced without prior permission
- 20. Mendel’s law of independent assortment • When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters. All right copy reserved. No part of the material can be produced without prior permission
- 21. Law of incomplete dominance • F1 generation progenies show an intermediate character, none of the parental traits is expressed. For example in a cross between true breeding red flower ( RR ) and true breeding ( rr ) , the F1 is pink ( Rr ). All right copy reserved. No part of the material can be produced without prior permission
- 22. Law of co-dominance • F1 generation resembles both parents. For example when IA and IB are present together they both express own types of sugars. All right copy reserved. No part of the material can be produced without prior permission
- 23. A gene which produces normal enzyme gets modified / mutated , the possible outcomes are: • the normal / less efficient enzyme. • a non – functional enzyme • no enzyme at all All right copy reserved. No part of the material can be produced without prior permission
- 24. Multiple alleles • ABO blood groups are controlled by the gene I. The gene I has three alleles IA, IB and i. Each person possesses any two of the three alleles. Due to six different combinations of these three alleles, a total of six different genotypes of human blood types are possible. All right copy reserved. No part of the material can be produced without prior permission
- 25. A single gene product produces more than one effect • homozygous ( BB ) produce large round seeds because of effective starch synthesis. • homozygous ( bb ) have lesser efficiency in starch synthesis , hence produce small, wrinkled seeds. • heterozygotes ( Bb ) produce round seeds of intermediate size All right copy reserved. No part of the material can be produced without prior permission
- 26. Chromosomal theory of inheritance • Proposed by Walter Sutton and Theodore Boveri • Chromosomes as well as genes occur in pairs. • The two alleles of a gene pair are located on homologous sites on homologous chromosomes. • Pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried. All right copy reserved. No part of the material can be produced without prior permission
- 27. Mendel’s work remained unrecognized • Communication was not easy in those days. • His concept of factors as stable and discrete units that controlled expression of traits and, of the pair of alleles which did not blend with each other was not accepted by his contemporaries. • Mendel’s approach of using mathematics to explain biological phenomena was totally new and unacceptable to many of the biologists of his time. • Mendel could not provide any physical proof for the existence of factors. All right copy reserved. No part of the material can be produced without prior permission
- 28. Rediscovery of Mendel’s work • Hugo De Vries, Karl Correns and Eric Von Tshermak independently rediscovered Mendel’s work. All right copy reserved. No part of the material can be produced without prior permission
- 29. Morgan selected Drossophila melanogaster • They could be grown on simple medium in the laboratory. • They complete their life cycle in about two weeks, and a single mating could produce a large number of progeny flies. • There was a clear differentiation of the sexes. • It has many types of hereditary variations that can be seen with low power microscope. All right copy reserved. No part of the material can be produced without prior permission
- 30. Linkage • Physical association of genes on a chromosome All right copy reserved. No part of the material can be produced without prior permission
- 31. Recombination • Formation of non parental combinations All right copy reserved. No part of the material can be produced without prior permission
- 32. Exception of law of independent assortment • When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combinations is much higher than the non-parental types. All right copy reserved. No part of the material can be produced without prior permission
- 33. Creation of genetic maps • Recombination frequency between gene pairs on the same chromosome is used as a measure of the distance between genes. More is the distance between genes, more is the recombination frequency. By determining recombination frequency we can map genes on the chromosomes All right copy reserved. No part of the material can be produced without prior permission
- 34. Sex determination • XX-XO type • XX-XY type • ZZ-ZW type All right copy reserved. No part of the material can be produced without prior permission
- 35. Pedigree analysis All right copy reserved. No part of the material can be produced without prior permission
- 36. Mendelian disorders • Haemophilia • Cyctic fibrosis • Sickle cell anemia • Colour blindness • Phenylketonuria • Thalesemia All right copy reserved. No part of the material can be produced without prior permission
- 37. Chromosomal disorders • Klinefelter’s syndrome • Down syndrome • Turner syndrome All right copy reserved. No part of the material can be produced without prior permission
- 38. Mutation • Mutation results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism All right copy reserved. No part of the material can be produced without prior permission
- 39. Frame shift mutation • Deletions and insertions of base pairs of DNA, causes frame-shift mutations. All right copy reserved. No part of the material can be produced without prior permission
- 40. Point mutation • Change in a single base pair of DNA All right copy reserved. No part of the material can be produced without prior permission
- 41. Mutagen • Physical and chemical factors that induce mutations All right copy reserved. No part of the material can be produced without prior permission