Difference Between Repetitive DNA and Satellite DNA

Main Difference – Repetitive DNA vs Satellite DNA

Repetitive DNA and satellite DNA are two types of DNA found in the genome of most eukaryotes. The main difference between repetitive DNA and satellite DNA is that repetitive DNA is small sequences of DNA that are repeated hundreds or thousands of times whereas satellite DNA is highly repetitive DNA sequences, constituting a considerable part of the genome. The two types of repeats found in the genome are tandem repeats and interspersed repeats. Satellite DNA consists of many tandem repeats of a short basic repeating unit. It is located on specific chromosomes of the human genome and near the centromeres of the chromosomes.

Key Areas Covered

1. What is Repetitive DNA
     – Definition, Fats, Types
2. What is Satellite DNA
     – Definition, Facts, Types
3. What are the Similarities Between Repetitive DNA and Satellite DNA
     – Outline of Common Features
4. What is the Difference Between Repetitive DNA and Satellite DNA
     – Comparison of Key Differences

Key Terms: Interspersed Repeats, Microsatellites, Minisatellites, Repetitive DNA, Satellite DNA, Tandem Repeats

What is Repetitive DNA

Repetitive DNA refers to the stretches of DNA that repeat throughout the genome. It represents some amount of the non-coding DNA spread throughout the euchromatin. The repetitive unit may consist of few base pairs to hundreds of base pairs. The average size of the repetitive unit is 300 bp. It may be repeated for 10-10⁵ copies per genome. The two main types of repetitive DNA are tandem repeats and interspersed repeats. Tandem repeats are shown in figure 1.

Figure 1: Tandem Repeats

In tandem repeats, the copies of a repetitive sequence unit lie adjacent to each other, forming a block, or an array. Satellite DNA is a type of tandem repeats. In interspersed repeats, the repetitive sequences are dispersed throughout the genome as single units flanked by unique sequence. The transposable elements such as DNA transposons and retrotransposons are interspersed repeats.

What is Satellite DNA

Satellite DNA refers to short, repetitive, DNA sequences often found in centromeric regions of the genome. It is the main functional units of the centromere. Satellite DNA is also found in the heterochromatin as a major structural constituent.  In the human genome, satellite DNA can be found in chromosomes 1, 9, and 16 and the short arms of chromosomes 13-15, 21, and 22. Satellite DNA is a type of tandem repeats. It is composed of short nucleotide sequences around 60 bp that are repeated more than 10⁶ times in the genome. The two main types of satellite DNA are minisatellites and microsatellites. A minisatellite sequence is shown in figure 2.

Figure 2: Minisatellite DNA

Minisatellites consist of 10-60 base pairs in the repeating unit. They are located in many places in the genome including centromeres. Microsatellites consist of less than 10 base pairs in the repeating unit, and they are mainly found in the telomeres.

Similarities Between Repetitive DNA and Satellite DNA

• Repetitive DNA and satellite DNA are two types of DNA found in the eukaryotic genome.
• Both repetitive DNA and satellite DNA consist of repeating sequence units.
• Both repetitive DNA and satellite DNA are types of non-coding DNA.
• Both repetitive DNA and satellite DNA do not code for proteins.
• Both repetitive DNA and Satellite DNA are located in intergenic regions.
• Both repetitive DNA and satellite DNA are important in maintaining the structure of the genome.

Difference Between Repetitive DNA and Satellite DNA

Definition

Repetitive DNA: Repetitive DNA refers to the stretches of DNA that repeat throughout the genome.

Satellite DNA: Satellite DNA refers to the short repetitive DNA sequences often found in centromeric regions of the genome.

Types of Repetitive Sequences

Repetitive DNA: Repetitive DNA consists of either tandem repeats or interspersed repeats.

Satellite DNA: Satellite DNA consists of tandem repeats.

Size of the Repetitive Unit

Repetitive DNA: Repetitive DNA may consist of few base pairs to hundreds of base pairs in the repetitive unit.

Satellite DNA: Satellite DNA consist of short repeating units (up to 60 base pairs long). 

Degree of Repetition

Repetitive DNA: Repetitive DNA is moderately repetitive sequences (10-10⁵ repeats per genome).

Satellite DNA: Satellite DNA consists of highly repetitive sequences (>10⁶ repeats per genome).

Located in

Repetitive DNA: Repetitive DNA is located in the intergenic regions of the genome.

Satellite DNA: Satellite DNA is located on specific chromosomes and centromeres of the chromosomes.

Types

Repetitive DNA: The two main types of repetitive DNA are tandem repeats and interspersed repeats.

Satellite DNA: The two main types of satellite DNA are microsatellites and minisatellites.

Role

Repetitive DNA: Repetitive DNA serves as an evolutionary device, catalyzing the formation of new genes.

Satellite DNA: Satellite DNA have a major role in DNA fingerprinting.

In CsCl Density Gradient analysis

Repetitive DNA: Repetitive DNA appears as light bands.

Satellite DNA: Satellite DNA appears as small dark bands.

Conclusion

Repetitive DNA and Satellite DNA are two types of DNA repeats found in the genome. Repetitive DNA are moderately-repeated DNA sequences while Satellite DNA are highly-repeated, short DNA sequences. The main difference between repetitive and satellite DNA is the degree of repetition.

Reference:

1.López-Flores, I., and M.A. Garrido-Ramos. “The Repetitive DNA Content of Eukaryotic Genomes.” Karger Publishers, 25 June 2012, Available here.
2.Garrido-Ramos, Manuel A. “Satellite DNA: An Evolving Topic.” Genes, MDPI, Sept. 2017, Available here.

Image Courtesy:

1. “VNTR2individuals5or7repeats” By Madelyndotson – Own work (CC BY-SA 4.0) via Commons Wikimedia