chromosomes

Definition: The self-replicating genetic structures of cells containing the cellular DNA that bears in its nucleotide sequence the linear array of genes. In prokaryotes, chromosomal DNA is circular, and the entire genome is carried on one chromosome. Eukaryotic genomes consist of a number of chromosomes whose DNA is associated with different kinds of proteins.

During 97% of a cell’s life its DNA is streched out into a thread like structure. Along the DNA strand several enzymes and other proteins are attached like beads on a string. When the cell is preparing to duplicate, it condenses all of its DNA by folding and twisting these structures into small packages called chromosomes. Every cell in the human body contains 46 chromosomes, of those 46 chromosomes 23 are inherited from each parent.

Chr.1	Chr.2	Chr.3	Chr.4	Chr.5	Chr.6	Chr.7	Chr.8	Chr.9
Chr.10	Chr.11	Chr.12	Chr.13	Chr.14	Chr.15	Chr.16	Chr.17	Chr.18	Chr.19
Chr.20	Chr.21	Chr.X	Chr.Y

Structure

Each human chromosome contains two specialized structures, a centromere and two telomeres .

The centromere divides the chromosome into short (p) and long (q) arms and is essential for the segregation of chromosomes during cell division.

The telomeres "cap" the p and q arms and are important for the structural integrity of the chromosome, for complete DNA replication at the ends of the chromosome, and for the establishment of the three-dimensional architecture of the nucleus.

Visualization

Chromosomes are isolated at the metaphase or prometaphase stage of the cell cycle and are treated chemically (e.g., by enzymatic digestion and staining with a DNA-binding dye) to reveal specific patterns of light and dark bands that are microscopically visible.

Analysis of the distribution of bands on individual chromosomes allows the identification of structural chromosomal abnormalities.

Types

 metacentric chromosome
 acrocentric chromosome

Pathology

 chomosomal anomalies

See also

 chromosomal rearrangements

• chromosomal translocations
• chromosomal deletions

 chromosomal instabilities
 chromosome positioning

Chromosomes

humpath	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
ensembl	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
hugo	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
ncbi	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
CGAP	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y

Oncogenetics

humpath	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
cancer-genetics.org	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
AGCOH	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y
progenetix	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	X	Y

Links

 Chromosomes at HUGO

Pathology

 chromosome-centric mapping of disease-associated genes

References

 Mechanisms of chromosome behaviour during mitosis. Walczak CE, Cai S, Khodjakov A. Nat Rev Mol Cell Biol. 2010 Feb;11(2):91-102. PMID: 20068571

 Gartler SM. The chromosome number in humans: a brief history. Nat Rev Genet. 2006 Aug;7(8):655-60. PMID: 16847465

 Harman OS. Cyril Dean Darlington: the man who ’invented’ the chromosome. Nat Rev Genet. 2005 Jan;6(1):79-85. PMID: 15630424

 Belmont AS. Visualizing chromosome dynamics with GFP. Trends Cell Biol. 2001 Jun;11(6):250-7. PMID: 11356361