64 WJEC Biology AS Level - Study And Revision Guide - Neil Roberts (1.6 The Cell Cycle And Cell Division)

Question 1

Describe the key differences of meiosis 1 compared to mitosis?

Answer 1

Following interphase, meiosis 1 follows a series of steps similar to mitosis except for the following differences:

There is a modified prophase 1 when homologous pairs come together to form bivalents and crossing over may occur.
This increases genetic variation.

The other major difference occurs during metaphase 1, when bivalents align randomly at the equator.
This is known as independent assortment.
This gives a further 8388608 variants from 23 bivalents i.e. 2 to the power of 23.

Question 2

What are the stages in meiosis 1?

Answer 2

1. Interphase
2. Prophase 1 (Key difference - crossing over can occur)
3. Metaphase 1 (Key difference - bivalents align)
4. Anaphase 1 (Key difference - chromosomes are pulled to opposite poles)
5. Telophase 1
6. Cytokinesis

Question 3

Meiosis 1 - Interphase

Answer 3

Question 4

Meiosis 1 - Prophase 1

Answer 4

Question 5

Meiosis 1 - Metaphase 1

Answer 5

Question 6

Meiosis 1 - Anaphase 1

Answer 6

Question 7

Meiosis 1 - Telophase 1

Answer 7

Question 8

Meiosis 1 - Cytokinesis

Answer 8