Role of repitive sequences

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Lumi
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Role of repitive sequences

Post by Lumi » Fri Aug 26, 2005 6:34 pm

50% of the human genome is repititive DNA which also do not encode for proteins. What is then their role in the genome?

ushishir
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Post by ushishir » Sat Aug 27, 2005 11:05 am

This extremely large fraction of human DNA is composed of many different types of sequence and so serves many different roles and none.

These roles include the regulation of the expression of genes - when and where genes are turned 'on' and 'off'

There are genes that code for RNAs only - these small 'micro-RNAs' are typically about 22 nucleotides long and play roles in regulating gene expression and development, although most of their functions are not known.

There are also various self replicating genetic elements that exist in huge numbers in the human genome alu alone numbers about 500,000 compared to about 30,000 protein coding genes. About 45% of the human genome is composed of these elements. These elements can play many roles in the human including disrupting genes, promoting certain types of mutation and they can be co-opted to play a role in gene expression, although most seem to have no effect on the host.

telomeres are repeats that serve a special role at the ends of chromosomes, stopping the ends from being lost.

There are also microsatellites
"A class of repetitive DNA that is made up of repeats that are 2–8 nucleotides in length. They can be highly polymorphic and are frequently used as molecular markers in population genetics studies."

and minisatellites
"A class of repetitive sequences, 7–100 nucleotides each, that span 500–20,000 bp, and are especially located throughout the genome, towards chromosome ends."

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