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Chromosomes

A cellular structure containing genes. Excluding sperm and egg cells, humans have 46 chromosomes (23 pairs) in each cell.

PubMed Health Glossary
(Source: NIH - National Institute of General Medical Sciences)

Image of chromosome inside the nucleus of a cell Click to enlarge

Parts of a chromosome and chromosomes inside the nucleus of a cell National Institutes of Health

About Chromosomes

A chromosome is an organized package of DNA found in the nucleus of the cell.

Different organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes - 22 pairs of numbered chromosomes, called autosomes, and one pair of sex chromosomes, X and Y.

Each parent contributes one chromosome to each pair so that offspring get half of their chromosomes from their mother and half from their father.

(More about Chromosomes)
NIH - National Human Genome Research Institute

Terms to know

Base Pairs
A base pair is two chemical bases bonded to one another forming a "rung of the DNA ladder." The DNA molecule consists of two strands that wind around each other like a twisted ladder.
Cells
The basic subunit of any living organism; the simplest unit capable of independent life. Although there are some single-celled organisms, such as bacteria, most organisms consist of many cells that are specialized for particular functions.
Centromere
A centromere is a region of a chromosome that separates it into a short arm (p) and a long arm (q). The chromosome consists of two identical structures called sister chromatids, which are joined at the centromere.
Chromatid
A chromatid is one of two identical halves of a replicated chromosome. The chromosome consists of two identical structures called sister chromatids, which are joined at the centromere.
Deoxyribonucleic Acid (DNA)
The molecular basis of heredity; encodes the genetic information responsible for the development and function of an organism and allows for transmission of that genetic information from one generation to the next.
Genes
A unit of genetic material (DNA) inherited from a parent that controls specific characteristics. Genes carry coded directions a cell uses to make specific proteins that perform specific functions.
Nucleus
In biology, the structure in a cell that contains the chromosomes. The nucleus has a membrane around it, and is where RNA is made from the DNA in the chromosomes.
P Arm
The chromosome's short arm.
Q Arm
The long arm on the chromosome.
Sperm
The male reproductive cell, formed in the testicle. A sperm unites with an egg to form an embryo.
Telomeres
The ends of a chromosome. Each time a cell divides, the telomeres lose a small amount of DNA and become shorter. Over time, the chromosomes become damaged and the cells die.

Related conditions

Terms to know

Base Pairs
A base pair is two chemical bases bonded to one another forming a "rung of the DNA ladder." The DNA molecule...
Cells
The basic subunit of any living organism; the simplest unit capable of independent life. Although there are s...
Centromere
A centromere is a region of a chromosome that separates it into a short arm (p) and a long arm (q). The chrom...
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