lecture 3

allelic interactions

presence of more than one gene occupying the same locus

genetic interference

genes are not independent but rather linked on one chromosome

what are the cases of allelic interference

1. incomplete dominance

2. Codominance

3. lethal allele

4. deactivate gene

incomplete Dominance

lack a dominance and recessive interactions among themselves

example of Incomplete Dominance

Antirrhinum majus

Dominance meaning in biochem

if the amount of the enzyme is sufficient for the enzyme to do it full role then its complete dominance if not its incomplete dominance

Co-Dominance

each allele has the ability to express to a certain degree

example of of co-dominance

short-horned cows and andalusian chicken

lethal allele

causes death of a carrier if its found in pure form

example of dominant lethal gene

yellow mice

example of recessive lethal gene

maize seedling

lethal genes in human

1. Ichthyosis vulgaris

2. Brachphalangy

3. Idiocy

Ichthyosis vulgaris

recessive inherited skin disorder

Brachphalangy

recessive short fingers

Inheritance of Idiocy

recessive neurodegenerative disorder

epistatic gene

a gene that makes the phenotypic effect of another gene

hypostatic gene

whose phenotype is altered by expression of an allele at a separate locus

F2 generation of deactivate gene

9:3:3:1

phenotype ratio of recessive epistasis

4yellow:3green:9red

phenotype ratio of dominant epistasis

1blue: 3yellow: 12red

phenotype ratio of duplicate recessive epistasis

7green : 9red

phenotype ratio of duplicate dominant epistasis

1blue : 15red

phenotype ratio of dominant recessive interaction

3yellow : 13red

phenotype ratio of polymeric gene interaction

1blue : 6green : 9red