Repetitive DNA and Telomer Replication

What is classified as a non-protein coding region

Cis-regulatory elements, non-protein coding RNAs, repetitive elements

Highly repetitive DNA

Short sequences repeated a large number of times

What is the only type of highly repetitive DNA

Satellite DNA

Satellite DNA

Main component of centromeres and structural constituent of heterochromatin

Centromere

Constricted region of the chromosome; where sister chromatids are held together and are A-T rich

Variable Number Tandem Repeats (VNTRs)

Occur at many locations in the human genome

How to ID with VNTRs

Use primers to flank VNTR region, run on gel to see fingerprint and separate by size; more repeats means a longer PCR product

Short Tandem Repeats (STRs) compared to VNTR

Shorter (about 2-9 bp), but are repeated 7-40 times

Steps to STRs

Follows the same process as VNTRs, but may use capillary electrophoresis since they are smaller samples

How to use STRs to ID an individual

Usually look at three or more loci to convincingly identify a subject; loci come from a set of 20 established STR loci

Tandem repeats

Repeats are consecutive

Interspersed retrotransposons

Spread throughout the genome; repeat sequences are not right next to each other

Transposon

Consists of inverted terminal repeats flanking a transposase open reading frame

Where do transposable elements originate from

Viral organisms

Cut and paste interspersed retrotransposon

Transposase physically cuts the transposon out of the genome and inserts it into a new location

Copy and paste interspersed retrotransposon

Retrotransposon encodes reverse transcriptase and integrase

Reverse transcriptase

Makes a DNA copy of the retrotransposon RNA

Integrase

Inserts the new retrotransposon DNA copy into the genome

Function of the telomerase complex

Extends the ends (telomeres) of linear chromosomes

Function of telomerase RNA component (TERC) in telomere extension

Serves as a guide for telomerase by bringing it to the telomere and as a template for DNA synthesis

Function of telomerase reverse transcriptase (TERT) in telomere extension

Uses TERC as a template sequence to extend the DNA

Function of RNA primase and DNA polymerase in telomere extension

Synthesizes the lagging strand so the template sequence stays intact

Shelterin

Protein complexes that protect telomeres, along with a unique loop structure