FOM 5.1.2 Flashcards
Only 30% of conception events lead to live births, what is one of the main causes for this?
Chromosomal abnormalities leading to early spontaneous abortions
What pattern does DNA replication follow?
semi-conservative
DNA is always polmerized in what direction? What must be present?
5’ to 3’, template strand
In what phase does DNA replication occur? How long does it take?
S phase, 6-12 hours
What are the 5 main steps of DNA synthesis?
See image
What is some important info about human origins of replication?
Some sequence bias: AT-rich CpG islands, variable depending on cell, transcriptionally active
Describe the directionality of human DNA replication.
Bidirectional, leading strand and lagging strand
An increased # of origins leads to what result?
Faster transcription
What binds the ORI?
ORC (origin recognition complex)
What couples w/ ORC to attract the helicase? What are the two components of the helicase?
cdc6; MCM helicase w/ cdt1 After MCM is bound w/ ORC, cdt1 and cdc6 dissociate
What is the name of the inhibitor of Cdt1?
Geminin
What are the three machinery involved in the replicative complex?
1)Primase enzyme (RNA->DNA) 2)DNA Polymerase deta/epsilon 3) Topoisomerase I
What binds to ssDNA to protect it after DNA is unwound by MCM?
RPA (replication protein A)
What are the two steps in the synthesis of the primer for replication?
1) Primase: 10-15 nt RNA 2) DNA pol alpha ~30 nt DNA onto RNA
What interacts w/ DNA pol d/e to help it stay bound to ssDNA?
PCNA
The leading strand creates a continuous strand whereas the lagging strand is discontinuous and makes ____.
Okazaki fragments
What does topoisomerase I do?
It creates a single stranded nick that allows for unwinding, which prevents “overwinding”
What links together the okazaki fragments?
DNA ligase by creating a phosphodiester bond
What removes and moves histones during DNA replication?
Chaperones
What problem is solved by telomerase?
It’s a reverse transcriptase that can preserve telomere length on the lagging strand.
Describe the telomere length over time in the three cell types (germ, stem, normal somatic)
See image
What is true about telomere length in persons with an increased mortality risk?
Shorter
As perceived affluence increases, what happens to the telomeres?
Longer
What is the mechanism of action of Acyclovir in the treatment of herpes? Foscarnet?
Chain terminator; DNA polymerase inhibitor (noncomp - blocks pyrophosphate binding site)
