3.14- Chromosomes

Recall that the nucleus of a cell contains chromosomes on which genes are located

Chromosomes:

• Contains genetic information within a cell, in a nucleus of a cell. 
• Chromosomes is composed of DNA and this forms a shape known as a double helix. Sections of this molecule are called genes. 
• One chromosome will have many genes. Each gene carries the information for the construction of a protein.
• This gives the characteristic associated with a gene. For instance- blood group.
• Different organisms have a different amount of chromosomes: 
• Cat- 38
• Chicken- 78
• Chimpanzee-42
• Human-46
• Chromosomes operate in homologous pairs and the nature depends upon the length of the chromosomes.

If we look at a gene, the position is known as a gene loci. If we go to the same position on the homologous we find the same gene loci. Therefore we have 2 versions of each gene. This version is called alleles.