QuestionSBA
QuestionChoice
Primer addition is a vital process in DNA replication in both bacteria and eukaryotes and is mediated by DnaG in bacteria and primase in eukaryotes. In eukaryotes, there is an extra step in which a DNA primer is added by DNA Pol-alpha. Further differences exist such as the removal of primers in bacteria by DNA Pol-1 via nick translation, compared to the removal of RNase H1 and flap endonuclease-1 then replacement by DNA pol-delta in eukaryotes.
10001114
d
Primase adds RNA primers to DNA strands, providing a basis for DNA polymerase activity on the leading strand and Okazaki fragments
QuestionChoice
The 5' m7G cap of mRNA is required by most mRNAs for binding to the small ribosomal subunit. This can however be overcome by internal ribosome entry sites on some eukaryotic and viral mRNAs resulting in cap-independent translation.

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10001115
e
The 5' m7G cap of mRNA mediates binding to the 40S subunit of the eukaryotic ribosome
QuestionChoice
This is the spindle assembly checkpoint (SAC). When the SAC is satisfied, CDC20 is released and bound to APC/C, allowing it to ubiquitinate securin (and cyclin B) for degradation. Securin inhibits separase, so the ubiquitination of securin dis-inhibits separase which then cleaves the Scc1 component of cohesin. This allows chromatid separation by the contractile forces of kinetochore-microtubule depolymerisation, initiating anaphase.
10001113
c
Once each kinetochore is attached to two microtubules from opposite poles, anaphase can begin
QuestionChoice
This is replication licensing, the process by which a finite number of the available origins are selected to be utilised before DNA replication begins to avoid under-replication or re-replication of the DNA.
10001111
a
Loading of MCM2-7 helicases onto origins of DNA replication
QuestionChoice
This occurs during the signalling that initiates replication, but is not replication licensing. Once Myc is activated, it promotes the transcription of Cyclin D which binds to CDK4 which in turn phosphorylates the retinoblastoma protein so that it can dissociate itself from E2F1. E2F1 then promotes Cyclin E transcription, moving the cell cycle from the G0 to G1 stage.
10001112
b
Mitogens act through tyrosine kinase receptors, activating Ras-Raf-Mek-MAPK signalling which activates pro-mitogenic transcription factors such as Myc
Concept
Chapter
2693
3885
Processes in mitosis
Topic
156
Medical Genetics
12769
Initiated by CyclinE/CDK2, which of the following describes replication licensing?
a