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#repetitive DNA

3 public questions tagged with this topic.

Eukaryotic chromatin and chromosome

Constitutive heterochromatin is rich in:

Constitutive heterochromatin stays condensed throughout cell cycle, lacks protein-coding genes and replicates late in S phase. Molecularly it consists of tandem repetitive satellite DNAs clustered at centromeres, telomeres and secondary constrictions, such as alpha satellite, Satellite III and minor satellites. These repeats bind SUV39H1 methyltransferase generating H3K9 trimethylation that recruits HP1 oligomers and DNMT3B for DNA methylation, enforcing silencing and suppressing recombination. It forms visible chromocenters and provides structural roles in sister cohesion and segregation rather than encoding active transcripts, permanently repressed in all cell types.

Ref: NCBI Bookshelf, Molecular Biology of the Cell, Chapter 4: Constitutive Heterochromatin Satellite DNA; Lewin Genes XII

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Molecular Marker

Which of the following is noncoding and highly repeated?

Genomic composition includes low-copy coding sequences and high-copy repetitive fractions with distinct functions. Satellite DNA comprises tandemly repeated, noncoding sequences organized as large continuous arrays at centromeres, telomeres and constitutive heterochromatin, further subdivided into microsatellite, minisatellite and macrosatellite classes based on repeat unit length. Highly reiterated and largely transcriptionally inert, it contributes to centromere function, heterochromatin formation and chromosome segregation fidelity. SNPs are single-base variants, exons are coding regions, ESTs represent transcribed tags. Noncoding reiterated organization defines satellite DNA distinction from low-copy functional sequences.

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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