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Look them up in the online glossary .

 

For AQA syllabus A AS module 2 make sure that you can answer the following questions.

In meiosis one cell divides into;
2
 8
 4
 3

 

The number of chromosomes at the end of meiosis is;
half the original number
 the same as the original number
 double the original number
 varies
The term haploid means;
the cell has the wrong number of chromosomes
 the cell has double the correct number of chromosomes
 the cell has homologous pairs of chromosomes
 the cell has one chromosome from each homolgous pair

 

 

Try to follow the stages of meiosis in this animation. Look how the homologous chromosomes separate in the first meiotic division and the chromatids separate in the second meiotic division.

 

Happy with this? Try the Biology Project tutorial from the University of Arizona

MEIOSIS

 

In meiosis diploid cells divide to produce four daughter cells each of which is haploid. It is the type of cell division requires to produce gametes.

For AQA syllabus AS Module 2 you do not need to know the details of cell division in meiosis. This is part of A2 Module 5.

First Meiotic Division

1. Prophase 1 The homologous chromosomes pair up, each chromosome consists of two chromatids. Chiasmata and crossing over occurs. The homologous chromosomes exchange portions of chromosome.

2. Metaphase 1. The chromosomes line up in pairs at the spindles equator. Chiasmata may continue.

3. Anaphase 1 The homologous chromosomes separate to opposite poles while the chromatids of each chromosome stay together.

4. The daughter nuclei from the first division contain a chromosome from each homologous pair. No DNA synthesis or chromosome duplication has taken place (telophase 1)

5. In the second meiotic division the chromosomes behave as in mitosis. One chromatid of from each chromosome goes to each of the poles (metaphase II, anaphase II). Two spindles have formed in the one cell.

6. Thus each cell entering meiosis produces four daughter cells. Each homologous chromosome segregates independently of the other.