- In prokaryotes, most of the DNA in a genome codes for protein products. A small amount exists as noncoding regulatory sequences like promoters. In contrast, 97 percent of the sequences in eukaryotic genomes do not sequence for protein products. Some of these noncoding sequences are made up of repetitive DNA. • Scientists can determine whether or not a sequence of DNA has multiple copies by denaturing the DNA and observing how fast the strands reanneal. DNA sequences that contain multiple repeats reanneal faster than sequences that exist as a single copy. • Two major types of repetitive DNA are tandemly repetitive DNA and interspersed repetitive DNA.

Tandemly repetitive DNA

- accounts for 10 to 15 percent of mammalian DNA. The lengths of the units are only 1-10 base pairs long, but the sequences may be repeated hundreds of thousands of times, one after the other. - Tandemly repetitive DNA is also referred to as satellite DNA because when genomic DNA is cut up into segments and centrifuged, pieces containing tandemly repetitive sequences will form a band separate from the rest of the DNA segments.

Interspersed repetitive DNA

- accounts for 25 to 40 percent of mammalian DNA. The length varies from 100 to 10,000 base pairs. Interspersed repetitive DNA sequences are scattered throughout the genome unlike tandemly repetitive DNA, which occurs one after the other. Often the dispersed sequences are similar rather than identical to each other.

Which of the following statements regarding repetitive DNA sequences is incorrect?

- Repetitive DNA sequences do not code for proteins.

Interspersed repeats account for

- more of the repetitive DNA than tandem repeats.

Tandemly repetitive DNA is also referred to as satellite DNA because

- it separates from the rest of genomic DNA when centrifuged.

6.9.2 Eukaryotic Genomic Organization: Repetitive DNA Flashcards by Irina Soloshenko

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6.9.2 Eukaryotic Genomic Organization: Repetitive DNA Flashcards

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