DNA and Nucleic Acids Flashcards
What group varies between ribose and 2-deoxyribose?
Ribose contains a hydroxyl group on carbon 2, whereas 2-deoxyribose does not
What are the components of a nucleoside?
A base plus a pentose sugar
What are the components of a nucleotide?
A base, a pentose sugar and a phosphate group(s)
What are the 5 bases of DNA and RNA?
Adenine
Guanine
Cytosine
Thymine
Uracil
Which bases are Purines?
Adenine
Guanine
Which bases are Pyrimidines?
Uracil
Thymine
Cytosine
What is the nucleoside of adenine?
Adenosine
What is the nucleoside of cytosine?
Cytidine
What is the nucleoside of guanine?
Guanosine
What is the nucleoside of thymine?
Thymidine
What is the nucleoside of uracil?
Uridine
What are the 5 building blocks of DNA and RNA?
dATP (deoxy-adenosine-triphosphate)
dCTP (deoxy-cytidine-triphosphate)
dGTP (deoxy-guanosine-triphosphate)
dTTP (deoxy-thymidine-triphosphate)
dUTP (deoxy-uridine-triphosphate)
Which group on DNA allows joining of nucleotides?
Free 3’ (on carbon 3) Hydroxyl group
In which direction can DNA grow?
It only grows in the 3’ direction
How do triphosphate nucleotides join onto DNA?
A phosphate anhydride bond breaks and the remaining phosphate group joins to the free 3’ OH of the DNA strand. A pyrophosphate is formed (2 phosphates)
What is meant by antiparallel?
DNA strands run in opposite directions
Which anti-retroviral drug is an analogue of thymidine?
Zidovudine (ZDV) / Azidothymidine (AZT) / Retrovir (Brand)
How does ZDV/AZT work?
AZT is incorporated into the viral DNA during reverse transcription. The OH group on carbon 4 allows it to be attached to the DNA strand, however it has a 3 Nitrogen chain on carbon 3, so the chain can’t continue as there is no OH.
Why does AZT not affect human DNA?
Viral reverse transcriptase has a higher affinity for ZDV than human DNA polymerase
What is an origin of replication?
An area in which the unzipping of DNA begins, forming a replication bubble
What are the 2 types of strand during DNA replication?
Leading and lagging
What is a leading strand?
A new strand that grows towards the replication fork, and so towards the 5’ end of the template strand
What is a lagging strand?
A new strand that grows away from the replication fork, so must be formed in segments called Okazaki fragments
What is an Okazaki fragment?
A section of DNA that forms up to the next DNA strand on the lagging strand
What joins Okazaki fragments?
DNA Ligase
What forms a primer?
A primase enzyme
What is a primer?
A short section of DNA that is formed to begin a strand. It later degenerates
What enzyme is responsible for proofreading?
DNA polymerase
What enzyme is responsible for unzipping the DNA strand?
DNA helicase
