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.
Egg and Sperm and Chromosomes
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)
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).