Genetics

Question 1

Epistasis

Answer 1

One gene (at a specific locus) affects another gene at another locus
The epistatic gene is the one causing the effect

Question 2

Sex-limited Inheritance

Answer 2

Genes are located on autosomal chromosomes, but the genotype is modified by sex hormones (such as testosterone) to influence expression of the trait
Appearance is limited to one sex or the other

Question 3

Sex-influenced Inheritance

Answer 3

Genes are located on autosomal chromosomes, but the genotype is modified by sex hormones (such as testosterone) to influence expression of the trait
Appearance is usually similar in both genders but different in frequency

Question 4

Polygenic Inheritance

Answer 4

Trait encoded by multiple different genes

Additive effect of multiple alleles contributing to a phenotype (each allele having no dominance over one another

Question 5

Penetrance

Answer 5

The percentage of genotype individuals who express the expected phenotype (imperfect penetrance is observed when one has the correct genotype but does not show the phenotype)

Question 6

Expressivity

Answer 6

The degree of penetrance
Qualitative (mild, intermediate, severe, etc.)
Only some of the traits associated with a phenotype may be displayed, even if there is a 100% penetrance

Question 7

Multifactorial Inheritance

Answer 7

multiple phenotypes and environmental factors influence this trait

Question 8

Barr Body

Answer 8

An X-chromosome that is mostly inactivated
The number of Barr bodies is equal to the number of X-chromosomes subtracted by one
Most girls only have one (although some may have two) and boys do not have any
Every cell decides (in early development) which copy is a Barr Body, creating a mosaic