Biology - Genetics

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  • Created by: Smartieee
  • Created on: 29-12-12 13:58

Diploid = 46
Haploid = 23

Women have two X chromosomes (in their 23rd pair)
Men have an X and a much smaller Y chromosomes (in their 23rd pair)
In the first 22 pairs the chromosomes in men and women are the same shape and size.

Allele - a version of a gene.

Each allele codes for a different form of the same character, e.g. earlobes that are free or earlobes that are attached.

Mutations - a sudden change in the DNA (i.e. chromosome or gene) of a cell
Mutations take place as the DNA is replicated as a cell divides.

Many mutations are harmful e.g.  Cancers
Many a neutral the same protein is made, so there is not much difference.
And some are beneficial
They are random and natural. Some factors increase the RATE of mutations, e.g. Ionising radiation.

If a mutation takes place in the 23rd pair (I.e. sex cell) it maybe passed on to the next generation - genetic disorder.

Whole chromosome mutations often results in the death of a cell, too many or too few chromosomes are passed onto the next generation
E.g. 3 copies of chromosome 21 results in downs syndrome

Young animals…


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