4.-NON-MENDELIAN-PATTERNS-OF-INHERITANCE.pptx

Non-mendelian genetics involves the pattern of inheritance that does not follow Mendel's laws. It describes the inheritance of traits linked to a single gene on chromosomes. When scientists began exploring more and more test crosses, they observed that there are several traits that do not match up with Mendel's laws

1. NON-MENDELIAN PATTERNS OF INHERITANCE

2. OVERVIEW TOPICS Law of Incomplete Dominance Law of Codominance Law of Multiple Allelism

3. MENDELIAN VS NON-MENDELIAN GENETICS Mendelian traits are determined by dominant and recessive alleles of one gene. Non-Mendelian traits are not determined by dominant and recessive alleles and can be governed by more than one gene.

4. NON-MENDELIAN GENETICS It involves the pattern of inheritance that does not follow Mendel’s laws.

5. It is not determined by dominant and recessive alleles but governed by more than a single gene.

6. INCOMPLETE DOMINANCE The heterozygote displays a phenotype that is an intermediate between the phenotypes of both homozygote parents.

7. In snapdragon plant, if a homozygous white flower is crossed with a homozygous red flower, a pink flower is obtained.

8. Chestnut brown Creamy white Palomino X

9. Sometimes, neither of a pair of alleles is completely dominant or completely recessive. Instead of one of them completely hiding the effect of the other in a heterozygote, they both have an effect on the phenotype . This is called codominance . The result is that there can be three different phenotypes.

10. CODOMINANCE Occurs when the phenotypes of both parents are simultaneously expressed in the same offspring.

11. Most of the genes exist in two alternative forms having different phenotypic effects called alleles which occupy the same locus in the homologous chromosome.

12. However, there are several genes that exist in more than two alternative forms called multiple alleles, which control alternative forms of the same character and they occupy the same locus in a pair of homologous chromosomes.

13. MULTIPLE ALLELES Refers to the existence of more than two different alleles for a single gene in a population.

14. These alleles can have various effects on an organisms phenotype.

15. Four alleles exist for the c gene. The wild-type version, C+C+, is expressed as brown fur. The chinchilla phenotype, cchcch, is expressed as black-tipped white fur. The Himalayan phenotype, chch, has black fur on the extremities and white fur elsewhere. The albino, or “colorless” phenotype, cc, is expressed as white fur.

16. In cases of multiple alleles, dominance hierarchies can exist. In this case, the wild-type allele is dominant over all the others, chinchilla is incompletely dominant over Himalayan and albino, and Himalayan is dominant over albino. This hierarchy, or allelic series, was revealed by observing the phenotypes of each possible heterozygote offspring.

17. Inheritance of A, B, AB and O Blood Group - an example of codominance

18. In humans, there are 4 blood types (phenotypes): A, B, AB, and O . Blood type is controlled by 3 alleles: IA, IB, IO (the base letter = I stands for immunoglobulin).

19. Can a child with blood type O be produced from parents with blood types A and B?

20. What blood types are possible among the children of a cross between a man who is blood type A and a woman of blood-type B?

21. In 1941, Charlie Chaplin met a young actress named, Joan Barry with whom he had an affair. The affair ended in February 1942 but 20 months later, Barry gave birth to a baby girl and claimed that Chaplin was the father. Barry then sued for child support. At this time, blood typing had just come into widespread use, and Chaplin’s attorney had Chaplin, Barry, and the child blood-typed. Barry had blood type A, her child had blood type B and Chaplin had blood type O. Could Chaplin have been the father of Barry’s child?

22. A mother and her child have blood type O. Which blood group can the father NOT belong to?

23. THANK YOU