Mendelian Inheritance.ppt
- 2. Let’s Review
- 3. Mendelian Inheritance Presented by Aeman Adnan M.Mubashir Fatima Manzoor Maryam Sadiq Mubashir Hussain
- 4. “Introduction to Mendelian Inheritance" • Gregor Mendel, an Austrian monk, is renowned for his pioneering work in the field of genetics. • Mendel's research, conducted in the mid-19th century, laid the foundation for our modern understanding of heredity.
- 5. Why Mendel choose Pea plant • Pea plants were ideal for controlled breeding due to their easily distinguishable traits. • Mendel observed several traits including Seed color (yellow or green) Seed shape (round or wrinkled) Flower color (purple or white) Flower position ( axial or terminal) Pod color (green or yellow) Pod shape (inflated or constricted) plant height (tall or short) • He meticulously conducted controlled crosses, controlling which plants were bred with each other.
- 6. Mendel's Discoveries: • Mendel introduced the concept of dominant and recessive alleles. • Dominant alleles are expressed when present, while recessive alleles are only expressed when two recessive alleles are inherited. • He identified specific ratios for trait inheritance, such as the 3:1 ratio for dominant to recessive traits. • Mendel's discoveries demonstrated that heredity follows specific rules and can be predicted mathematically.
- 7. The Implications of Mendel's Work : • Mendel's work has broad implications in genetics. In agriculture, it underpins crop breeding by selecting for desirable traits. • In medicine, understanding Mendelian inheritance is essential for studying genetic disorders and inherited diseases. • In evolutionary biology, Mendelian inheritance explains how genetic diversity within species is maintained.
- 8. Mendelian Inheritance and Modern Genetics: • Mendel's legacy endures in modern genetics as his laws continue to be a cornerstone of genetic research. • His meticulous approach to experimentation and his foundational discoveries have shaped the field of genetics for over a century.
- 9. Three laws of Hereditary There are three laws proposed by Mendel Law of segregation Law of independent Assortment Law of Dominance
- 10. Law of Dominance Definition When two organisms homozygous pure for two different trait, their offspring hybrid is heterozygous in which one allele suppress the effect of another allele. The traits are controlled by two factors that can be called ‘’dominant’’ or ‘’recessive.’’ A ‘’dominant’’ trait that shows if the offspring inherits at least one dominant factor from one Parent. A ‘’recessive’’ trait that shows only if the offspring inherits two recessive factors, one from each Parent.
- 11. Example when pea plants with Yellow color seeds (gg) are crossed with plants with green color seeds (GG), all seeds in F1 generation were found to be round (Gg). All seven traits studied by Mendel.
- 12. Limitations The law is not applicable for all living organisms as it is only valid in the case of diploid organisms and the organisms that undergo sexual reproduction.
- 13. Principle The law (or the principle) of dominance states that the presence of a dominant allele will always mask the presence of a recessive allele. Complete dominance is a form of dominance in the heterozygous condition wherein the allele that is regarded as dominant completely masks the effect of the allele that is recessive.
- 14. Law of Segregation Also known as First law of inheritance. It describes How a alleles for a particular trait segregate or separate during the formation of gametes (sex cells: sperms and egg) in sexually reproducing Organisms
- 15. Example Results Purple is dominant over white Phenotypic ratio of F2 generation is 3:1 Genotypic ratio of F2 generation is 1:2:1
- 16. Limitations Law of segregation applies only to traits that completely control a single gene pair in which one of the two alleles is overriding the other. Therefore, the law of segregation does not apply to incompletely dominant or co-dominant alleles.
- 17. Law of Independent Assortment Introduction Law of independent assortment is stated that When two contrasting pairs of traits are followed in the same cross, their alleles assort Independently into gametes. The distribution of alleles of one trait into gametes has no influence on the distribution Of alleles of the other trait. Law of independent assortment was developed by studying dihybrid cross.
- 18. Phenotypic and genotypic expression
- 19. Limitations Genes are located on chromosomes at specific loci. Independent assortment of genes depends upon independent assortment of their chromosomes. All the genes present on a homologous pair of chromosomes are linked to each other in the form of a linkage group. These cannot assort independently. Those traits assort independently whose alleles are riding non homologous chromosomes
- 20. Exceptions of Mendelian Inheritance Mendelian inheritance refers to the patterns of inheritance described by Gregor Mendel, such as dominant and recessive alleles. There are several exceptions to Mendelian inheritance, including: Incomplete dominance Codominance
- 21. Incomplete Dominance Both alleles are expressed Partially Intermediate between both homozygotes Have different expressions e.g. R1 and R2 Same Phenotypic and Genotypic Ratio No need of test cross Example: Flower color in 4O’ clock plant
- 22. A cross between Red and white flowered plants produced plants with intermediate flower color e.g. pink color Ratio 1 : 2 : 1 Red: Pink: White Example
- 23. Codominance Both alleles are expressed fully. Distinct from both homozygotes Different expression e.g. M and N Have same Phenotypic and genotypic Ratio No need of test cross.
- 24. Example
- 25. Conclusion Why Mendelian Inheritance is important? • Gregor Mendel's pioneering work with pea plants provided us with the fundamental principles of heredity. • Understanding Mendelian inheritance is essential for comprehending how traits are passed from one generation to the next and how genetic diversity is maintained.