Meiosis

Question 1

What are the steps associated with Meiosis I?

Answer 1

1. Interphase
2. Prophase I
3. Metaphase I
4. Anaphase I
5. Telophase/Cytokinesis

Question 2

What happens during Interphase I?

Answer 2

The DNA in the cell is copied resulting in two identical sets of chromosomes.

Outside of the nucleus are two centrosomes, each containing a pair of centrioles (critical for the process of cell division).

Microtubules extend from these centrosomes.

2n = 6

Question 3

What happens during Prophase I?

Answer 3

The copied chromosomes condense into X-shaped structures. Each chromosome is composed of two sister chromatids containing identical genetic information. The chromosomes pair up and exchange bits of DNA in a process calling recombination or crossing over.

At the end, the membrane around the nucleus in the cell dissolves, releasing the chromosomes. The meiotic spindle then extends across the cell between the centrioles.

Question 4

What happens during Metaphase I?

Answer 4

The chromosome pairs line up next to each other along the center (equator) of the cell. The centrioles are now at opposite poles of the cell with the meiotic spindles extending from them. The meiotic spindle fibers attach to one chromosome of each pair. There are 2^n possibilities

Question 5

What happens during Anaphase I?

Answer 5

Sister chromatids are pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole.

Question 6

What happens during Telophase I/Cytokinesis?

Answer 6

The chromosomes complete their move to the opposite poles of the cell and a membrane forms around each set of chromosomes to create two new daughter cells.

n = 3

Question 7

What are the steps associated with Meiosis II?

Answer 7

1. Prophase II
2. Metaphase II
3. Anaphase II
4. Telophase II/Cytokinesis

Question 8

What happens during Prophase II?

Answer 8

The nuclear membrane dissolves and spindles form. The centrioles begin to move to opposite sides of the cell.

Question 9

What happens during Metaphase II?

Answer 9

The sister chromatids are lined up in the middle of the cell by spindle fibers. This is different from Metaphase I where the homologous pairs lined up side-by-side.

Question 10

What happens during Anaphase II?

Answer 10

The sister chromatids are pulled apart by the spindles towards opposite sides of the cell.

Question 11

What happens during Telophase II/Cytokinesis?

Answer 11

The spindles dissolve and new nuclear envelopes appear. A cleavage furrow forms and the cytoplasm separates until fou rhaploid cells are produced. They are unique and different from one another.