NON-MENDELIAN PATTERNS OF INHERITANCE.pptx

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1. NON – MENDELIAN PATTERNS OF INHERITANCE

2. Allele pairs may have a variety of dominance relationships. There are often many different alleles of a gene in a population.

3. Non- Mendelian inheritance - is a general term that refers to any pattern of inheritance which does not follow Mendel’s laws.

4. Non- Mendelian inheritance Incomplete Dominance Codominance Multiple Alleles

5. 1. INCOMPLETE DOMINANCE Occurs when the dominant alleles does not completely mask the phenotypic expression of the recessive alleles. Neither of the alleles present is dominant or recessive. A heterozygote phenotype appears which is intermediate between the two homozygote phenotypes.

6. Sample Problem: In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (W). What if two pink- flowered snapdragon plants were crossed, what will be the resulting offspring?

7. 2. CODOMINANCE Occurs when both alleles are dominance. Both alleles are simultaneously expressed in the heterozygote.

8. Sample Problem: In some cows, the gene for coat color is controlled by codominance. The alleles for black coat is B and the allele for white coat is W. Show the resulting offspring when a black cows is crossed with a white cow. What if two spotted cows were crossed, what will be resulting offspring?

9. 3. Multiple Alleles Most human genes have more than two normal versions or alleles. Although individual humans (and all diploid organisms) can only have two alleles and individuals in the population may have different pairs of these alleles. EXAMPLES: Coat color in rabbit – is determined by a single gene that has at least four different alleles. Different combinations of alleles result in the four colors you see here.

10. Sample Problem: If a pure rabbit is crossed with another rabit with chinchilla coloration, what will be the resulting offspring?