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2.1.8 ­ Meiosis

In sexual reproduction, the offspring are genetically different from each other and from the parents.
Each parent produces special reproductive cells, called gametes. Gametes (one from each parent) fuse
together during fertilisation to produce a zygote.

The chromosome number must be halved
When two gametes fuse to…

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Meiosis II
This division is in a plane at right angles to meiosis I.

Prophase II
If a nuclear envelope has reformed it breaks down again.
The nucleolus disappears, chromosomes condense, and spindles form.

Metaphase II
The chromosomes arrange themselves at the equator of the spindle. They are attached to…

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Fertilisation
In humans only one ovum is released from an ovary at a time (usually). There are about 300 million
spermatozoa, all genetically different and any one of them can fertilise the ovum, genetic material
from the two unrelated individuals is combined to make the zygote.

Mutation
DNA mutation may…

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