dna replication + recombination quiz Flashcards
Which enzyme unwinds the parental DNA molecule by breaking the hydrogen bonds that hold the two strands together?
DNA helicase
Because DNA polymerase III can only act from 5’ to 3’, continuous strand growth can be achieved only along one of the template strands (leading strand), and strand growth along the other strand must occur discontinuously resulting in the production of a series of short sections of new DNA. What are these sections called?
Okazaki fragments
Replication occurs once every cell generation during?
S phase
what are most of the mistakes during DNA replication are corrected by?
DNA polymerase III
which enzymes joins Okazaki fragments?
DNA ligase
true or false
Because of the antiparallel nature of the DNA double helix, the direction of DNA synthesis for leading and lagging strand are opposite. Because of this, the two DNA polymerase molecules involved physically move in opposite directions
false
what is the role of dna topoisomerases?
relieve supercoils that accumulate in front of active replication forks
true or false
DNA polymerase III builds new strands from scratch during DNA replication.
false
why is dna replication said to be semiconservative?
a new double helix contains one old and one new strand
Why is an RNA primer necessary for DNA replication?
DNA polymerase can only add nucleotides to an existing strand
In DNA recombination, the junction that forms is called a…
holliday junction
what are the features of dna recombination?
- 4 strands of DNA are involved (i.e. 2x double strands)
- Genetic exchange (%cross-over%) takes place between a pair of homologous DNA sequences
- Heteroduplex regions (areas of mismatch) are formed
- Heteroduplex regions are repaired by mismatch repair
- Horizontal cleavage of the junction will not produce recombinants.
when does recombination occur?
during meiosis
