What is the function of SAT chromosome?

Satellite or SAT chromosomes are chromosomes that contain secondary constructs that serve as identification. They are observed in Acrocentric chromosomes. In addition to the centromere, one or more secondary constrictions can be observed in some chromosomes at metaphase.

Is heterochromatin transcribed?

Heterochromatin is not transcribed and comes in two forms: facultative heterochromatin and constitutive heterochromatin (Fig. 8.11).

Why is it called satellite DNA?

The name “satellite DNA” refers to the phenomenon that repetitions of a short DNA sequence tend to produce a different frequency of the bases adenine, cytosine, guanine and thymine, and thus have a different density from bulk DNA such that they form a second or ‘satellite’ band when genomic DNA is separated on a …

What are secondary constriction and satellite chromosomes?

Genes for 5S rRNA are present on chromosome 1. Due to secondary constriction, a knob-like structure is formed at the end called a satellite chromosome (SAT chromosome). DNA in a secondary constriction which forms rRNA is called rDNA.. NORs occur in SAT chromosomes (13,14,15,21,22).

What is the role of satellite DNA in DNA fingerprinting?

Satellite DNA shows polymorphism which forms the basis of DNA fingerprinting. There are short nucleotide repeats in the DNA which are specific in each individual and vary in number from person to person but are not inherited. These are called ‘variable number tandem repeats’ or mini-satellites.

What is the difference between satellite DNA and repetitive DNA?

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.

Is euchromatin or heterochromatin transcribed?

Euchromatin is the transcriptionally active form of chromatin. On the other hand, heterochromatin exists in condensed form and is usually present toward the end or pericentric region of the chromosome. Inside the nucleus, heterochromatin could be seen near the periphery and are often clumped.

Why are genes in heterochromatin not expressed?

The two types of chromatin, heterochromatin and euchromatin, are functionally and structurally distinct regions of the genome. Heterochromatin is densely packed and inaccessible to transcription factors so it is rendered transcriptionally silent (Richards and Elgin 2002).

What is minisatellite and microsatellite?

Conclusion. Microsatellite is a type of repetitive DNA in the eukaryotic genome with a 2-6 base pairs long repetitive sequences. They are widespread throughout the genome and can be used for paternity testing. On the other hand, minisatellite is a type of repetitive DNA with 10-100 base pairs long repetitive sequences.

What is the difference between primary and secondary constriction?

The centromere of chromosome is known as primary constriction. The chromatids of a chromosome may be attached together by the primary constriction region On the other hand, any other constricted region over a chromosome is called secondary constriction.

What is a satellite chromosome and kinetochore?

Satellite repeats are predominantly located in centromeric and pericentromeric regions of chromosomes. Centromeres are chromosomal sites for assembly of kinetochores, protein complexes that attach to spindle fibers and mediate separation of chromosomes during cell division.

Where is satellite DNA located on the chromosome?

Most satellite DNA is localized to the telomeric or the centromeric region of the chromosome. The nucleotide sequence of the repeats is fairly well conserved across species.

What is the monomer length of the satdna sequence?

The monomer length of satDNA sequences ranges from 150 to 400 bp in the majority of plants and animals. satDNA sequences are located at heterochromatic regions, which are found mostly in centromeric and subtelomeric regions in the chromosomes but also at intercalary positions.

What is the length of satellite DNA?

Length. Most satellite DNA is localized to the telomeric or the centromeric region of the chromosome. The nucleotide sequence of the repeats is fairly well conserved across species. However, variation in the length of the repeat is common. For example, minisatellite DNA is a short region (1-5kb) of repeating elements with length >9 nucleotides.

What are the two types of satellite DNAs?

Satellite DNAs are about 1.3kb and are of two types: the nanovirus-like DNA 1 or alphasatellites, and the DNA B-like DNA β or betasatellites. From: Viruses, 2018