Chromosomes are thin strands of DNA (deoxyribonucleic acid).

They are subdivided into genes.

In most cells, chromosomes are located in functional pairs in the nucleus.


Humans have 46 chromosomes arranged in 23 pairs.

In contrast, gametes do not have pairs of chromosomes in their nuclei and bacterial cells do not have a nucleus.

The entire genetic material of an organism is known as the genome.


A gene is a short length of DNA found on a chromosome that codes for a particular characteristic or protein.

Alleles are variations of the same gene. For example, eye colour is the gene but blue, green, brown etc. are alleles.