B1 Genes

Jeans for genes sounds familiar. This is where you wear jeans to raise money for research into genes.  But what are genes, where are they found and what to they do?

Well, lets start at the very beginning, let's zoom in on a cell.

First of all, you must be able to draw and label a plant and animal cell.

Inside the nucleus there are long strands of DNA. 

Each strand forms a chromosome.
Now chromosomes are divided up into genes.

So the chromosomes are found inside the nucleus. The nucleus contains different chromosomes and these are arranged in pairs. Humans have 23 pairs of chromosomes. Notice in the diagram below the chromosomes at the end are an X and a Y. This tells you that this is a male. If there were 2 X chromosomes it would be a female.

Different chromosomes contain different genes and each gene does a particular job. Eg. many of these genes control what we look like, hair and eye colour, ear lobes etc.

Variation caused by genes is called inherited variation - yes it's back to variation again! This is because we inherit our genes from our parents, 1/2 from mum and 1/2 from dad.

So genes carry the code or instructions for a certain characteristic. Some genes for the same characteristic may have 2 slightly different versions which give slightly different instructions to make differences and variations. These different forms of a gene are called alleles. There are different alleles for your eye colour eg. brown or blue.

Summarising all this then, there are 2 copies of each chromosome in the nucleus and there are 2 copies of every gene that makes up the chromosome called alleles.

Exam tip - if you are asked about characteristics and genetic then talk about alleles not just genes.