Module 02 - Section 04 Flashcards
DNA Repair
What is a karyotype
Visualization of the number and appearance of the chromosome within a cell, where each chromosome pair is labelled with a different colour
What is recombination?
Rearrangement of genetic material, especially by crossing over in chromosomes
What are two prime examples of problems that occur within a cancer cell?
(1) Aneuploidy
(2) Chromosomal translocation
What is aneuploidy?
Presence of an abnormal number of chromosomes in a cell
What causes aneuploidy? (2)
Mitotic segregation defects or chromosomal non-disjunction.
What is chromosomal non-disjunction?
Failure of one or more pairs of homologous chromosomes or sister chromatids to separate nomrally during and after mitosis
What is chromosomal translocations?
Abnormality caused by rearrangement of parts between non-homologous (not part of the same pair)
- can be direct swtiching of material between 2 chromosomes of large scale deletions/insertions
What generally causes chromosomal translocations?
Errors during homologous recombination or double strand break repair
What is a DSB?
Double-strand break is a break in the phosphodiester backbone on both strands of DNA at the same site
When and why do DSBs occur?
(1) During replication, when replication fork encounters a single-strand break in the template strand, which then become a DSB because DNA breaks make it impossible for DNA replication to continue
(2) Exposure to UV or gamma radiation - result goes beyond a simple mutation that may or may not affect cellular function, typically lead to cell death
Which bacteria can withstand tremendous amounts of radiation because of its DNA regeneration?
Deinococcus Radiodurans
How does deinoccocus radiodurans deal with radiation?
It contains many copies of its DNA to ensure there is always a back up template for repair. After radiation, overlapping DNA fragments are spliced together and the entire genome is reconstituted accurately within a few hours.
What is inherent to every free-living organism?
Capacity for the enzymatic repair of DSBs
What is recombinational DNA repair?
Group of recombination processes directed at the repair of DNA strand breaks or cross links, especially at inactivated replication forks.
What does recombinational DNA repair require?
Another undamaged, homologous, double stranded DNA – either the second copy of the chromosome or the sister chromatid