What is Chromosome 3?

By Dr. Ananya Mandal, MDReviewed by Sally Robertson, B.Sc.

Chromosome 3 is the third largest of the 23 pairs of chromosomes found in humans. It spans nearly 200 million base pairs, the building blocks of DNA, making up around 6.5% to 7% of the genetic material in the human genome.

Image Credit: NIH

Structure and functions of chromosome 3

Chromosome 3 is metacentric, meaning its centromere is positioned somewhere around its centre. There are several vital and important genes located on this chromosome including certain gene clusters that code for the olfactory receptors (involved in sense of smell) as well as chemokine receptors that aid inflammatory processes. Genetic research is focused on identifying the genes on our chromosomes and estimates suggest that chromosome 3 contains around 1100 to 1500 genes.

Some of the important genes that are present on chromosome 3 include:

On the short or "p" arm of the chromosome

• ALAS1 - codes for aminolevulinate, delta-, synthase 1 enzyme)
• BTD - (codes for biotinidase enzyme)
• CCR5 - codes for chemokine C-C motif receptor 5
• CNTN4 - codes for Contactin 4
• COL7A1 - codes for collagen type VII, alpha 1
• MITF - mutations result in microphthalmia-associated transcription factor
• MLH1 - mutatinos lead to colon cancer, nonpolyposis type 2
• PTHR1 - codes for parathyroid hormone receptor 1
• SCN5A - codes for voltage-gated, type , alpha sodium channel and mutation leads to Long QT syndrome 3
• SLC25A20 - codes for carnitine/acylcarnitine translocase
• TMIE - codes for transmembrane inner ear
• VHL - codes for von Hippel-Lindau tumor suppressor

On the long or "q" arm

• CPOX - codes for coproporphyrinogen oxidase
• HGD - codes for homogentisate 1,2-dioxygenase
• MCCC1 - codes for methylcrotonoyl-Coenzyme A carboxylase 1 alfa
• PCCB - codes for programmed cell death 10
• PIK3CA - codes for phosphoinositide-3-kinase, catalytic, alpha polypeptide
• RAB7 - an oncogene or cancer causing gene
• SOX2 - a transcription factor
• USH3A - mutation causes Usher syndrome 3A
• ZNF9 - codes for zinc finger protein 9 and nucleic acid binding protein

Further Reading

• All Chromosome 3 Content