Back to AI Flashcard MakerBiology /BIOL1020 - Lecture 4 - DNA structure and replication
what are nucleic acids?
deoxyribonucleic acid (DNA) - ribonucleic acid (RNA)
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Key Terms
Term
Definition
what are nucleic acids?
deoxyribonucleic acid (DNA) - ribonucleic acid (RNA)
describe DNA
stores information for the synthesis of specific proteins directs RNA synthesis directs protein syntheis through RNA
what are the possible methods of DNA replication?
semiconservative, conservative and dispersive
know the concepts and how the meselson-stahl experiment works
C14 and carbon 15
how does bacterial DNA replication (schematic) work?
replication starts at the origin - and proceeds in BOTH DIRECTIONS until the entire chromosome has been copied.
how do you unwind the DNA double helix without creating knots? (HINT KEY ENZYMES AND PROTEINS USED)
> helicase - untwists the DNA helix to give single stranded DNA, but increases coiling ahead of the replication fork topoisomerase - ‘fixes’ the incre...
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| Term | Definition |
|---|---|
what are nucleic acids? | deoxyribonucleic acid (DNA) - ribonucleic acid (RNA) |
describe DNA | stores information for the synthesis of specific proteins directs RNA synthesis directs protein syntheis through RNA |
what are the possible methods of DNA replication? | semiconservative, conservative and dispersive |
know the concepts and how the meselson-stahl experiment works | C14 and carbon 15 |
how does bacterial DNA replication (schematic) work? | replication starts at the origin - and proceeds in BOTH DIRECTIONS until the entire chromosome has been copied. |
how do you unwind the DNA double helix without creating knots? (HINT KEY ENZYMES AND PROTEINS USED) | > helicase - untwists the DNA helix to give single stranded DNA, but increases coiling ahead of the replication fork topoisomerase - ‘fixes’ the increase coiling in the DNA template by transiently nicking both strands and allowing the two strands to rotate around each other. single-stranded binding protein -stabilises the single strand template. |
how is new DNA synthesised? | uses nucleotide building blocks ALWAYS proceeds in 5’ to 3’ direction + energy for polymerisation is supplied by incoming triphosphate nucleotide DNA polymerase catalyse DNA synthesis |
how does synthesis work on the leading strand? | to start DNA synthesis the enzyme DNA primase synthesises an RNA primer the RNA primer is then extended by DNA polymerase III the RNA primers are removed by the action of the 5’ exonuclease activity of DNA polymerase I, with DNA synthesised in their place at the same time. |
describe DNA synthesis on the lagging strand | the basic mechanism of DNA synthesis is the same (5’-3’) BUT: new RNA primers have to be made frequently to keep DNA synthesis going this creates lots of DNA fragments (OKAZAKI fragments) DNA polymerase I removes the RNA primers DNA ligase joins the Okazaki fragments to create a continuous DNA strand |
what is the mechanism involved in DNA synthesis to correct mistakes? | DNA polyermases have exonuclease activities enables proofreading and editing Mismatched pair - DNA polymerases correct mismatched bases Nucleotide excision repair - requires the enzyme nuclease to remove bulky, damaged DNA components |
what leads to mutations? | if mismatched/damaged bases are not removed |
for non-circular DNA, where do you start/stop replication? | at multiple origins along the chromosome |
how do eukaryotic chromosomes remain full length? | the ends of chromosomes are called ‘telomeres’ telomeres usually do not contain coding regions the last part of linear DNA strand cannot be synthesised during ‘normal’ DNA replication. telomerase is an enzyme that creates an extension to the unreplicated end of the DNA strand. DNA primase and DNA polymerase III can then synthesis the lacking piece of DNA |
What is telomerase? | > An enzyme that creates an extension to the end of the un replicated end of the DNA strand. DNA primase and polymerase III can then synthesise the lacking piece of DNA |