Meiosis

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What is meiosis?

A form of nuclear division vital for sexual reproduction which takes place in the reproductive organs
What does meiosis result in?

It results in the formation of four haploid gametes from one diploid cell
Meiosis involves _____ consecutive cell divisions?

two
The _____ ____ ____ divides in two and the two divide again?

gamete mother cell
Meiosis produces four genetically _______ gametes?

different
Each of the four gametes formed contains ____ the number of chromosomes present in the original gamete mother cell?

half
Describe this stage of meiosis:
- Each chromosome doubles (DNA replication) to form two identical chromatids
- Each chromosome becomes thicker - forming a short coiled chromosome
Describe this stage of meiosis:

Homolgous chromosomes pair up
- Homologous chromosomes touch at certain points called chiasma
- Crossing over occurs at these points - the exchange of genetic material between the two homologous chromosomes
- Nuclear membrane disappears
- Spindle fibres form from the centrioles and attach at the centromeres of the chromosomes
- Homolgous chromosomes line up at the equator of the cell - independent assortment
Chromosomes are pulled apart by contraction of the spindle fibres and move to different poles
- The nuclear membrane reforms round each group of chromosomes
- The cytoplasm divides
- Two haploid cells are formed at the end of the first meiotic division
- Nuclear membrane disappears
- Spindle fibres form from the centrioles and attach at the centromeres of the chromosomes
- Chromosomes line up at the equator of the cell
Chromatids are pulled apart and move to different poles
Cytoplasm divides
- Nuclear membrane reforms
- Four genetically different haploid gametes are formed at the end of the second meiotic division

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Card Set

Meiosis

Description

Higher Biology - Unit Two - Meiosis

Updated

2011-11-30T14:53:52Z