Coding versus Noncoding DNA

Tandemly Repetitive DNA (Satellite DNA)

Shows repeated bands of satellite DNA on a chromosome next to a band of regular DNA.

Unknown source


Shows the location of telomeres and centromeres on a drawing of a chromosome. Zooms in on a picture of a telomere where the sequence TTAGGG is repeated.

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Tandemly Repetitive DNA Can Cause Diseases

Explains Fragile X syndrome. Explains Huntington's disease.

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Interspersed Repetitive DNA

Tandemly Repetitive DNA versus Interspersed Repetitive DNA

Tandemly Repetitive DNA Interspersed Repetitive DNA
Proportion of mammalian DNA 10–15 % 25–40 %
Length of each repeated unit 1–10 base pairs 100–10 000 base pairs
Relevant Numerical Characteristics Total length of repetitive DNA per site, in base pairs:
Regular satellite DNA 100 000–10 million
Minisatellite DNA 100–100 000
Microsatellite DNA 10–100
Number of repetitions per genome: 10–1 million
Notes Repeated units at a site are usually identical. “Copies” are very similar but not identical.

Some Repetitive DNA Sequences are Transcribed (But Don't Make Proteins): Multigene Families

Shows the processing of the genes for rRNA.

Figure 14.2, Purves's Life: The Science of Biology, 7th Edition


Pseudogenes are DNA sequences that are similar to real genes, but lack the regulatory sequences necessary for gene expression (e.g. promoters).

Transposons and Retrotransposons

Shows how a transposon can mess up a normal protein-coding gene. Shows the normal operation of a transposon.

Figure 14.3, Purves's Life: The Science of Biology, 7th Edition; Figure 19.5, page 350, Campbell's Biology, 5th Edition

Evolution of a Multigene Family: Hemoglobin Proteins

Demonstrates a hypothesis for the evolution of the two globin gene families.

Figure 19.3, page 349, Campbell's Biology, 8th Edition