Biology - B1 - You and your genes

You should know :

- Most of your features are affected by your environment and your genes.

That you inherit a lot of features such as eye colour, but weight is a characteristic that is down to what you eat, and so is environmental.

- Genes are found in the nuclei of cells and are instructions for making proteins.

Cell - Nucleus - Chromosomes - Genes - DNA. They can code to make structural proteins or enzymes, which speed up reactions.

- Your chromosomes, and genes are in pairs.

23 pairs. That's 46 chromosomes. 23 from your mother, and 23 from your father. The genes are in pairs, so they are in the same part of the chromosome of both chromosomes.

- Genes have different versions, called alleles.

Variations of a gene. So the gene for blue eyes is an allele (pronounced al - ee - al) of the gene for eye colour.

- The difference between dominant and recessive alleles.

Dominant alleles are written with a capital letter, for example, T. If you have a dominant gene, then you will have what it codes for. An example would be Huntingdon's disease. It is caused by a dominant allele. Recessive alleles are written in lower case, t. You need both recessive alleles to have what it codes for. Cystic Fibrosis is an example of a disease caused by recessive alleles. You can be a carrier of a recessive alleles, but you can't be a carrier of a dominant allele, only a sufferer.

- Men and women have different sex chromosomes.

Women have ** chromosomes, and men have XY. 

-How a gene on the Y chromosome causes an embryo to develop as a man.

SRY gene. (sex determining region of the y chromosome). This gene causes you to produce androgen (a hormone), which triggers the development of testes. If the gene isn't present, then neither is androgen and so the sexual organs become female.

-Why you may look like your parents.

You inherit your genes from your parents, and therefore you are quite likely to inherit ones that make you look quite similar to your parents. Because half your genes come from your…