B1: You and Your Genes

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.

< CHROMOSOME (Two of the X-shaped chromosomes would be a pair)

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.

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

The SEX CELLS
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)

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.

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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).