B1: You and Your Genes


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  • Created by: Kay
  • Created on: 27-04-11 15:38


In the CELL there is a NUCLEUS.

In the nucleus, there are 23 PAIRS of CHROMOSOMES.
>One type of chromosome from each of the parent.
>Thus, a total of 46 chromosomes are in the nucleus.

Each chromosome carries GENES.
>The coloured bands (shown below) are short lengths of gene which is a molecule of DNA. The DNA is coiled.

(http://2.bp.blogspot.com/_ucZFh1CYAOE/S7-Z7bWnbeI/AAAAAAAAAF8/6l3qKleHvak/s1600/chromosome.gif)< CHROMOSOME (Two of the X-shaped chromosomes would be a pair)

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When chromosomes come in pairs, they are for the same characteristics but are just a version from the mother, and another from the father. They are called alleles.

Genes will be used to make up proteins which in turn makes cells.

*Some of these proteins will be "structural". - Hair, skin, blood and cytoplasm (which is in our cells)

*Some of the proteins will be enzymes. The catalysts for chemical reactions - respiration and digestion.

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Egg and Sperm and Chromosomes

cells nucleus = 46 chromosomes
23 belong to the mother
23 belong to the father

Egg - from the female
Sperm - from the male

The above cells are different though.
They only have 23 chromosomes.

This is so, when the sperm and egg meet and fertilise they will have a total of 46 chromosomes (so, 23 pairs), the normal amount for a cell.

Each pair in a regular cell carry the same genes just one from each parent.

The alleles are the same genes that the chromosomes have in common which are slightly different. (Ie. Male allele = green eyes, the female allele = blue eyes)

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Chromosomes and Humans

Half of the chromosomes come from the male and the other half from the female.

A human will only have some alleles from each parent.


When humans produce sperm/egg cells, the pairs split up and go into different cells.
In a chromosome pair, neither one have identical genes because they have diffrerent allelels.
Thus, NO ONE IS IDENTICAL (unless you are an indentical twin).

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Jess Andrew


USEFUL. Thank you! 



This was really helpful. THANKS :)



Brilliant Help! 

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