Lec. 23 - Chromosomes

Question 1

Describe a test cross and a dihybrid cross.

Answer 1

A test cross is a genetic cross btwn. and organism displaying a dominant phenotype of unknown genotype and a homozygous recessive organism for the same trait. Dihybrid cross is a genetic cross involving two traits that are located on different gene pairs.

Question 2

Differentiate btwn. female and male genotypes.

Answer 2

Female genotypes have two X chromosomes, male genotypes only have one X chromosome.

Question 3

Differentiate btwn. somatic vs. sex-linked mutations.

Answer 3

Somatic mutations are genetic alterations that occur in somatic cells. Sex-linked mutations occur in the sex chromosomes.

Question 4

Explain x-inactivation and why it occurs.

Answer 4

It’s a process that occurs in females to compensate for the double dose of XX chromosomes. One of the two X chromosomes is randomly inactivated in each cell of the embryo.