Meiosis

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  • Created by: zoolouise
  • Created on: 24-04-16 14:28
Where does meiosis take place and what does it produce?
It takes place in the reproductive organs of plants, animals and some protoctistants, before sexual reproduction. It produces four genetically distinct haploid gametes.
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Why is the diploid number halved to haploid?
When the 2 haploid gametes fuse during fertilisation, zygote has 2 sets of chromosomes from each gametes. Restores haploid number, if halving didn't happen, the number of chromosomes would double every generation.
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What is Prophase I?
Homologous chromosomes form a bivalent Crossing over of sister chromatids causes a chiastmata to form. Chromosomes will coil, shortening and thickening. Spindle fibres will form. Nuclear envelope disintegrates.
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What is Metaphase I?
The bivalents arrange themselves on the equator of the cell. Chromosomes are attached to the spindle fibres by their centromeres.
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What is Anaphase I?
The spindle fibres shorten and the chromosomes separate going to opposite poles of the cell.
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What is Telophase I?
Nuclear envelope forms around each set of chromosomes and chromosomes start to uncoil. Spindle fibres start to break down.
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What occurs in Cytokinesis after Meiosis I?
The division of the cytoplasm making two haploid cells.
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What is Prophase II?
The centrioles separate and organsie a new spindle at right angles to the old spindle
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What is Metaphase II?
Chromosomes align themselves on the equator, each chromosome is attached to the spindle fibres by their centromere. Independent assortment happens as the chromatids of the chromosome can face either pole.
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What is Anaphase II?
Centromeres divide. Spindle fibres shorten, pulling chromatids to opposite poles of the cell.
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What is Telophase II?
The chromatids uncoil and lengthen. The spindles disintegrate and the nuclear envelope and nucleoli re-form.
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What is Cytokinesis after Meiosis II?
The cytoplasm splits creating four haploid daughter cells.
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Other cards in this set

Card 2

Front

Why is the diploid number halved to haploid?

Back

When the 2 haploid gametes fuse during fertilisation, zygote has 2 sets of chromosomes from each gametes. Restores haploid number, if halving didn't happen, the number of chromosomes would double every generation.

Card 3

Front

What is Prophase I?

Back

Preview of the front of card 3

Card 4

Front

What is Metaphase I?

Back

Preview of the front of card 4

Card 5

Front

What is Anaphase I?

Back

Preview of the front of card 5
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