ch.12 mendelian genetics

Question 1

What is the difference between a gene and a locus?

Answer 1

gene: factor that determines character
locus: position on chromosome responsible for character

Question 2

What is a genotype? How about a phenotype?

Answer 2

genotype: indicates what genes are present (AaBb)
phenotype: indicates what genes are physically expressed (AB)

Question 3

Describe what happens in nondisjunction.

Answer 3

In a nondisjunction, a mistake in meiosis occurs. Both homologues of one of the 23 chromosomes are pulled to the same side of the dividing cell, which results in no copy of one gamete and two copies in the other.

Question 4

Know the three ways that meiosis (and fertilization) promote variation in offspring.

Answer 4

1. independent assortment: metaphase I
2. crossing over: prophase I
3. random fertilization: fertilization occurs after meiosis

Question 5

Be able to describe what crossing over is and know when it occurs (phase of meiosis).

Answer 5

crossing over occurs in prophase I of meiosis, in which DNA breaks from each parent’s sister chromatid and recombines with each others DNA to create a new combination of both parent’s DNA

Question 6

Be able to do the same as in (9) for 2 loci that are close together on the same chromosome

Answer 6

Genes on the same chromosome, you can’t separate when finding genotypes