Telomers

Question 1

Telomers

Answer 1

Repeated DNA sequence at ends of chromosomes: TTAGGGn; forms loops at ends to avoid DNA repair mech and protects ends. Permits complete replication of chrom DNA and length determines number of replications. Telomerase maintains telomers = germ cells and react in cancers

Question 2

Telomerase

Answer 2

Protein RNA complex with 2 components
TERC - RNA template for synth telomere DNA repeats
TERT - reverse transcriptase. synth telomere DNA by copying telomere repeats encoded in RNA template (made of DNA)

Question 3

Telomerase reactivation

Answer 3

In cancers, not initiating event but important in cancer progression. Allows survival despite continuous and rapid divisions

Question 4

Dyskeratosis Congenita

Answer 4

1 mutated telomerase allele. Premature shortened telomers; affects rapidly dividing cells. Progressive BM failure leading to pancytopenia and immunosupp (death at 16). Epidermal structure abnormal (skin, hair, nails) and malignancy (chrom instab)

Question 5

Shortened Telomers

Answer 5

Somatic cell telomers shorten during succesive cell divisions. Reaching threshold tiggers senescence (G0) or arrest in G1, chromo instab if it continues. Telomere dmg activates p53 cell cycle arrest frequently followed by apoptosis

Question 6

Lack of Telomers

Answer 6

Lack of repeats leads to chromo instability and fusions = cell death/tumorgenesis (dicentric chromo formation)