3.3 and 10.1 Meiosis

Question 1

In what way is meiosis a reduction division?

Answer 1

Meiosis involved a halving of the chromosome number from 2n to n and is thus a reduction.

Question 2

Why is meiosis important to sexually reproducing organisms?

Answer 2

• Halving of chromosome number allows a sexual life cycle with fusion of gametes
• allows for genetic diversity
• fertilization doubles the number of chromosomes each time it occurs so meiosis prevents each generation having double the amount of chromosomes.

Question 3

Are the sister chromatids of one chromosome identical to each other?

Answer 3

Initially, yes, but DNA replication mistakes change that.

Question 4

Are the two homologous chromosomes identical to each other?

Answer 4

No, they are homologous but not identical and so map the same genes but can have different alleles.

Question 5

Define bivalents.

Answer 5

In early stages of meiosis, homologous pairs form bivalents. This consists of four sister chromatids and two homologous chromosomes. Bivalents are also called tetrads.

Question 6

What is the process of forming bivalents called? What occurs then?

Answer 6

It is called synapsis. During this time, crossing over occurs.

Question 7

When does crossing over occur? What is its effect?

Answer 7

• Crossing over occurs during Meiosis I.

- It yields chromatids with new combinations of alleles.