In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Chromosomes are not visible in the cell’s nucleus—not even under a microscope—when the cell is not dividing. However, the DNA that makes up chromosomes becomes more tightly packed during cell division and is then visible under a microscope. Most of what researchers know about chromosomes was learned by observing chromosomes during cell division.
Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes.
Genetic terms glossaries.
Common genetic disorders This list of genetic, orphan and rare diseases is provided for informational purposes only and is not comprehensive.
A-Z of Genetic Diseases (External)
Frequently Asked Questions
- Have question on Chromosome? Ask in the Question portal.
- FAQ's on Chromosome
- Frequently Asked Questions
Find something you can improve? Join WikiMD as an an editor and help improve this page or others.
- UpToDate on Chromosome
- Medline Plus Chromosome
- Most recent articles on Chromosome
- Most cited articles on Chromosome
- Ongoing Trials on Chromosome