Genetic Variation (II)

Question 1

Discontinuous variation

Answer 1

• A few distinct and discrete phenotypes
• Caused by different alleles of a single gene
• Generally unaffected by environment
• Represented by bar charts

Question 2

Continuous variation

Answer 2

• Phenotypes vary along a continuum (no distinct groupings)
• Polygenic: involves multiple genes with an additive effect on the phenotype
• Influenced by environment
• Bell-shaped normal distribution curve

Question 3

def. Epistasis

Answer 3

Epistasis is a form of gene interaction in which a gene at one locus affects the phenotypic expression of a gene at a second locus.

• Recessive epistasis: recessive allele of one gene, present in the homozygous condition, masks the phenotypic effects of alleles of the other gene.
• Dominant epistasis: dominant allele of one gene, present in either homozygous or heterozygous condition, masks the phenotypic effects of alleles of the other gene.