DNA Synthesis, Repair & Recombination 2 Flashcards
DNA recombination is the process that includes breakage, exchange, and rejoining of 2 parental DNA molecules to produce new DNA molecules. What are the two known types of recombination?
homologous - complementary strands of homologous DNA moluecules
nonhomologous - nonhomolohous DNA molecules
What is the potential consequence of not being able to keep homologous chromosomes together prior to Anaphase I of meiosis?
Abnormal numbers of chromosomes
ex: trisomy for chromosomes 15, 18, and 21
In response to a double stranded break, one of the first alterations to occur is a degradation of the 5’ end. What protein is responsible for this?
Exonuclease
Once the exonuclease has degraded the 5’ end, what enzyme is responsible for elongating the 3’ end? What does this result in?
DNA polymerase
migration of branch point
Once the gap has been filled in by DNA polymerase there is one final step in repairing the ds break. What is that step?
DNA ends are joined by ligation
Without referring to ploidy what is/are the product(s) of a diploid cell with one pair of homologous chromosomes after chromosome duplication and meiosis?
Produces (haploid) cells with chromosomes that have crossed over
Which of the following occurs during a double-stranded break DNA repair?
Homologous chromatid is used as a template
This conformation of DNA is four-stranded and produced by homologous recombination. What is the name of this conformation?
Holliday Junction
Once DNA ligase has joined the DNA strands (post DNA polymerase), there is the potential for (double) holliday junction to occur. In order to resolve the holliday junction(s) the structure(s) is cleaved and re-ligated forming two chromosomes that exchanged segments. What is the state of the new chromosomes regarding their genetic diversity?
Resolution of Holliday Junction(s) can result in chromosomes with or without crossover.
During meiosis there becomes the possibility of forming what is known as a heteroduplex (Double-stranded DNA in which the two strands are derived from different DNA molecules). What is the process by which this occurs?
Gene conversion
“The one way transfer of information resulting in an allele on one parental chromosome being changed to the allele from the other homologous chromosome”
*dont need to memorize exact definition just know what’s going on*
Should reciprocal translocation take place, there is a 50/50 chance the product will be stable or unstable in mitosis. What needs to happen in order to yield a stable product? Unstable?
Exchange of 2 acentric parts will yield a product that is stable in mitosis
Exchange of one centric and one acentric piece will yield an unstable product.
In Robertsonian translocation the products are acentric and dicentric chromosomes. Which of these products are stable in mitosis?
Dicentric = stable
Acentric = unstable
On which chromosomes does robertsonian translocation exclusively occur?
The short arm of chromosomes: 13, 14, 15, 21, 22
In comparing and contronstating repicrocal and robertsonian translocation, the gametes produced can give rise to unique genotypes. What are the genotypes in common and what are the genotypes that differ between the two processes?
Genotypes in common:
Normal
balanced carrier
Unique genotypes:
partial/ubalanced - reciprocal => ex: partial trisomy
Full monosomy or trisomy - Robertsonian => ex: monosomy 14, trisomy 21
What is a transposon?
A segment of DNA that can move from its original position in a genome to a new location
*can cause genetic instability by insertions or rearrangements*
