Meiosis

Question 1

What are the results of mitosis?

Answer 1

One cell becomes two genetically identical daughter cells with the same number of chromosomes.

Question 2

What is the result of meiosis? (General)

Answer 2

Genetic diversity among offspring!

Question 3

Haploid/Diploid (Ploidy)?

Answer 3

Refers to number of chromosome sets in a cell; Haploid - single set of unpaired chromosomes (n) & Diploid - two complete sets of chromosomes, one from each parent (2n)

Question 4

Homologous Chromosomes?

Answer 4

Two chromosomes in a pair - normally one inherited from the mother and one from the father; same size, shape, organization; they have the same genes, but may have different version of that gene

Question 5

Alleles?

Answer 5

One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

Question 6

Result of meiosis (Specific)

Answer 6

One diploid cell becomes four genetically unique haploid cells; gametes are produced via meiosis

Question 7

What happens in Interphase, Meiosis 1, and Meiosis 2?

Answer 7

Interphase: chromosomes duplicate, forming 2 identical sister chromatids

Meiosis 1: Homologous chromosomes “cross over” some genetic information, then separate

Meiosis 2: sister chromatids separate

Question 8

Prophase I

Answer 8

Homologous chromosomes pair up and crossing over occurs.

Question 9

What is crossing over?

Answer 9

A source of genetic variability. After interphase, the chromosomes have been duplicated and the sister chromatids are held together by proteins called cohesins.

Early in prophase I, the two members of a homologous pair associate loosely along their length. Each gene on one homolog is aligned precisely with the corresponding allele of that gene on the other homolog.

The DNA of two nonsister chromatids—one maternal and one paternal—is broken by specific protein complex at precisely matching points.

Next, the formation of a zipper-like structure called the synaptonemal complex holds one homolog tightly to the other. The chromatin continues to condense.

During this association, called synapsis, the DNA breaks are closed up so that each broken end is joined to the corresponding segment of the nonsister chromatid. Thus, a paternal chromatid is joined to a piece of maternal chromatid beyond the crossover point, and vice versa.