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Chromosome 7

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Chromosome 7

Chromosome 7 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 7 spans more than 158 million base pairs (the building material of DNA) and represents between 5 and 5.5 percent of the total DNA in cells.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 7 is likely to contain between 1,000 and 1,400 genes. It also contains the Homeobox A gene cluster.

Diseases and disorders

The following diseases are some of those related to genes on chromosome 7:

Chromosomal disorders

The following conditions are caused by changes in the structure or number of copies of chromosome 7:

  • Williams syndrome is caused by the deletion of genetic material from a portion of the long (q) arm of chromosome 7. The deleted region, which is located at position 11.23 (written as 7q11.23), is designated as the Williams syndrome critical region. This region includes more than 20 genes, and researchers believe that the characteristic features of Williams syndrome are probably related to the loss of multiple genes in this region.

While a few of the specific genes related to Williams syndrome have been identified, the relationship between most of the genes in the deleted region and the signs and symptoms of Williams syndrome is unknown.

  • Other changes in the number or structure of chromosome 7 can cause delayed growth and development, mental disorder, characteristic facial features, skeletal abnormalities, delayed speech, and other medical problems. These changes include an extra copy of part of chromosome 7 in each cell (partial trisomy 7) or a missing segment of the chromosome in each cell (partial monosomy 7). In some cases, several DNA building blocks (nucleotides) are deleted or duplicated in part of chromosome 7. A circular structure called ring chromosome 7 is also possible. A ring chromosome occurs when both ends of a broken chromosome are reunited.

References

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