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1. Beskrive hvordan generne er organiseret i det mammale (humane) genom

The haploid human genome consists of 3 x 10⁹ base pairs. Only about 2-4% of all these base pairs are structural gene, while the rest is junk-, telomere and centromere DNA. There are all in all 30.000 genes in the human genome.

The genes constitute of exons (expressing sequences) and introns (intervening sequences). The introns need to be spliced out and are not expressed in the finished protein. The expression of each gene is controlled by sequences lying prior to the gene (promoters) or thousands of base pairs away from it (enhancers).  

The genes lie on chromosomes – a DNA-helix lying in the nucleus.  There are 46 chromosomes in the human genome (22 pairs of autosomes and 1 pair of sex chromosomes). One of the chromosomes is of paternal origin, the other one of maternal.

Each individual has two copies of each gene, one of each parent. Which gene is expressed depends on the inheritance type.

At the end of the chromosomes there are telomeres, which prohibit loss of genetic material. During replication of the DNA, a centromere holds the two DNA-helices together.

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