Genetics

The human genome is stored on 23 chromosome pairs. The haploid human genome has a total of 3 billion DNA base pairs, making up an estimated 20,000- 25,000 protein-coding genes.

1.5% encodes protein, while 98.5% has regulatory or unknown function.

A typical gene has the following:

• a promoter that binds RNA polymerase
• a transcriptional start site, where production of RNA begins
• exons - which contain the coding sequence
• introns - non-coding sequence between exons
• a transcriptional stop site

Repeat sequences in DNA

Although the function, if any, of many repeat sequences is not known, some repeats, such as microsatellites and minisatellites, have been exploited by molecular biologists.

Minisatellites are used in 'DNA fingerprinting' and microsatellites have been employed as genetic markers owing to the variability of their length.

Minisatellites:

9-24 bp repeats often several kb in length; frequently subtelomeric, may function as recombination hotspots

Microsatellites (Short Tandem Repeats - STRs):

1-6 bp tandem repeats, usually several hundred bp long, randomly distributed, unknown function

Some uses of knowledge in molecular biology and genetics

• PCR
• DNA sequencing - including whole genome and exome sequencing