1. Lecture 11
LTRs
Properties of Chromatin
Telomeres

2. Human Genome is ‘over-inflated’

3. Two types of transposons

4. LTR retrotransposons constitute 8% of human DNA
443,000 endogenous retrovirus-related LTRs
(LTR = long terminal repeats)
Reverse transcriptase, Integrase, etc.

5. Very common LTR elements in yeast (Ty elements)

6. Retrotransposons without LTRs
Long interspersed elements (LINES), ~6 kb long, 21% of human DNA
A lot of them are silent, but there are ~60 active. The event of transposition occurs once in every 8-10 individuals.
Short interspersed elements (SINES), ~300 bp long, 6% of human DNA
Both are particularly abundant in mammals
Integrate into A-T rich regions, without using LTRs
Alu elements are most common SINES (~300 pb) scattered throughout the genome (named after the restriction enzyme, for which they have a site)
Processed pseudogenes are spliced mRNAs, back-transcribed into DNA and randomly inserted into the genome

7. Mobile DNA elements: role in evolution
Dispersed equal elements led to unequal crossover and gene duplication
Exon shuffling via recombination between homologous interspersed Alu repeats

8. Integration of an exon into another gene via LINE transposition

9. Please read “Evolvability”

11. Extended “Beads-on-a-string” chromatin
(low-ionic strength buffer)
Condensed Chromatin
(0.15 M KCl buffer)

19. SEM picture of a chromosome and Giemsa-stained caryotype

21. Three functional elements are required for replication and stable inheritance of chromosomes
ARS (autonomously replicating sequences)
CEN (centromeres) and TEL (telomeres)