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Recombination quiz #1

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  • Which type of bacterial mating is most likely to yield a recombinant cell?
    An Hfr x F- mating is most likely to yield a recombinant cell because the Hfr cell can transfer chromosomal genes to the F- cell through homologous recombination, resulting in new genetic combinations.
  • Which structures can be involved in homologous recombination?
    Structures involved in homologous recombination include single-strand nicks (breaks), double-strand breaks, cross bridge structures, and Holliday junctions, all of which facilitate the exchange of genetic material between homologous chromosomes.
  • What is branch migration in the context of homologous recombination?
    Branch migration is the movement of the cross bridge structure up and down the chromosome, allowing the region of genetic exchange to expand or contract.
  • What role does the RecA protein play during double strand break recombination?
    RecA helps process the double strand break by creating a 3' overhang and facilitating strand invasion for homologous pairing and repair.
  • How does a 3' overhang form during double strand break recombination?
    A 3' overhang forms when nucleotides are removed from one end of the broken DNA strand, creating a single-stranded region that can invade a homologous chromosome.
  • What is a Holliday Junction and what is its significance in recombination?
    A Holliday Junction is a cross-shaped structure formed during homologous recombination, allowing the exchange of genetic material between chromosomes and its movement along the DNA.
  • How can homologous recombination result in new allele combinations on chromosomes?
    By exchanging genetic material between homologous chromosomes, recombination can introduce different alleles or mutations into new genetic contexts.
  • What distinguishes gene conversion from standard homologous recombination?
    Gene conversion is a nonreciprocal exchange between closely linked but not identical genes, whereas homologous recombination involves reciprocal exchange at equivalent positions.
  • How does gene conversion affect allele ratios in gametes?
    Gene conversion can skew allele ratios, resulting in unequal distribution of dominant and recessive alleles, such as 3:1 instead of the expected 1:1.
  • What causes gene conversion during recombination?
    Gene conversion is caused by base pair mismatches during duplex formation, leading to nonreciprocal genetic exchange between similar but non-identical sequences.