17.8 Epistasis

Question 1

what is epistasis

Answer 1

• the allele of one gene affects or masks the expression of another in the phenotype
• occurs when genes on different chromosomes interact to influence the same phenotype

Question 2

what is a hypostatic gene

Answer 2

the gene whose expression is blocked by the epistatic gene

Question 3

what is recessive epistasis

Answer 3

• the epistatic gene must be homozygous recessive to block the expression of the hypostatic gene

Question 4

what is dominant epistasis

Answer 4

• the epistatic gene is dominant and actively modifies or blocks the expression if the hypostatic gene

Question 5

example of epistasis

Answer 5

• coat colour in mice
  1. gene A controlled the banding pattern of black pigment
• dominant allele produces agouti coat colour
• recessive causes black coat colour
  2. gene B controlled overall melanin production
• dominant allele allows melanin production
• recessive allele blocks melanin production resulting in albino white coat masking the effect of gene A alleles