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#DNA repeats

2 public questions tagged with this topic.

Molecular Marker

Which repeat type is >100 base pairs?

Tandem repetitive DNA is classified by repeat unit length and array size. Microsatellites, SSR or STR, contain 1-6 bp motifs, minisatellites or VNTR contain 10-100 bp motifs, while macrosatellites exceed 100 bp and can span kilobases, forming large heterochromatic blocks at centromeres, telomeres and heterochromatic regions. The greater than 100 base pair definition distinguishes macrosatellite organization, which often shows higher-order repeat structure, epigenetic silencing and copy number variation. Such large repeats are unsuitable for standard PCR microsatellite assays but crucial for ch

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Molecular Marker

Microsatellites vary in:

Microsatellites consist of tandemly repeated units of one to six base pairs dispersed throughout genomes. Variation among individuals originates from difference in copy number of repeat motifs at orthologous loci, caused by replication slippage leading to expansion or contraction of repeats. Base composition of repeat motif remains constant, for example CA dinucleotide, and genomic location is conserved. Length variation is secondary consequence of repeat number change. Therefore, allelic diversity at microsatellite loci directly reflects hypervariability in number of repeat iterations.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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