In plant and animal cells, DNA is securely wrapped into structures called chromosomes that resemble threads. This is in contrast to bacteria, whose DNA is free to circulate throughout the cell.
A single strand of DNA is wrapped several times around a large number of proteins called histones to form nucleosomes.
These nucleosomes then firmly wrap up to form chromatin loops. The chromatin loops are subsequently intertwined to form a whole chromosome.
Each chromosome is comprised of two short arms (p arms), two longer arms (q arms), and a centromere at its centre.
One set of 23 chromosomes is inherited from the mother and the other set is inherited from the father.
One pair of these 23 pairings are sex chromosomes, which differ depending on whether a person is male or female (XX for female or XY for male).
The remaining 22 pairs of chromosomes are autosomes, which appear identical in males and females.
Each of our chromosomes' DNA is composed of thousands of genes.
At the ends of each of our chromosomes are telomeres, which are pieces of DNA. During DNA replication, telomeres safeguard the ends of chromosomes by forming a cap, similar to the plastic tip on a shoelace.