20897342
Description
Flashcards by Blen Abate, updated more than 1 year ago
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Created by Blen Abate
almost 5 years ago
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| Question | Answer |
| What are histones used for? | they are used by the cell to package DNA into nucleosomes |
| Nucleosome | consists of a central core of 8 histone proteins with DNA coiled around them |
| What is supercoiling good for? | it allows a great length of DNA to be packed into a small space in the nucleus |
| How does replication happen on the leading strand? | the strand is made continuously following the fork as it opens |
| How does replication happen on the lagging strand? | the strand is made in fragments moving away from the fork |
| Direction of replication | 5' to 3' |
| coding sequences | the DNA sequences that code for the production of polypeptides |
| Helicase | unwinds and separates the double-stranded DNA by breaking the hydrogen bonds b/n base pairs, this happens at the origins of replication, creating a replication fork of two strands running in antiparallel directions |
| DNA gyrase | reduces the torsional stain created by the unwinding of DNA by helicase through negative supercoiling |
| Topoisomerase | releases the strain that develops ahead of the helicase |
| single-stranded binding proteins | bind to the DNA strands after they've been separated and prevent the strands from re-annealing, they also help prevent the single-stranded DNA from being digested by nucleases, they will be dislodged from the strand when a new strand is synthesized |
| DNA primase | generates a short RNA primer (~ 10-15 nucleotides) on each of the template strands, it provides an initiation point for DNA polymerase III, which can extend a nucleotide chain but not start one |
| DNA polymerase | covalently links the deoxyribonucleotide monophosphate to the 3' end of the growing strand |
| DNA polymerase III | attaches to the 3' end of the primer and covalently joins the free nucleotides together in a 5' to 3' direction, it moves in opposite directions on the two strands |
| DNA polymerase I | removes the RNA primers from the lagging strand and replaces them with DNA nucleotides |
| DNA ligase | joins the Okazaki fragments together to form a continuous strand, it does this by covalently joining the sugar-phosphate backbones together with a phosphodiester bond |
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