bsc2010 chapter 15 DNA replication

purine

purine

adenine and guanine are these, where adenine pairs with thymine (DNA) OR uracil (RNA) and guanine pairs with cytosine

• GA

pyrimidine

cytosine, thymine, and uracil are these, where cytosine pairs with guanine, thymine pairs with adenine (DNA), and uracil pairs with adenine (RNA)

• CUT

s-phase of interphase

this is when DNA replication happens in a eukaryotic cell

replication fork

y-shaped region where new DNA strands are elongating

semi-conservative

DNA replication is _______________ because the new DNA is made of an old strand and a new strand

origin of replication

eukaryotic cells have 100+ to 1000+ of these, causing cells to duplicate slower, but only one or few in prokaryotic bacterial cells

helicase

this enzyme opens the double helix “unzips the jeans”

single-strand DNA-binding proteins (SSBP)

holds strands apart, stabilizing single-stranded DNA

primase

this is a short sequence of RNA tagged to start an RNA chain from scratch, adding RNA nucleotides one at a time to make a starting point for the DNA polymerases; moves in the 5’→3’ direction as DNA polymerase can only add to the 3’ end

topoisomerase

relieves tension/overwinding by the helicase

DNA polymerase

enzymes that add nucleotides for DNA, ONLY attaches nucleotides to a preexisting 3’ end

• a new DNA strand only grows from 5’→3’

• they can also “proofread” and replace incorrect/damaged nucleotides

leading strand

DNA polymerase continuously synthesizes DNA towards the replication fork, DNA growing from 5’→3’

sliding clamp

holds the DNA polymerase in place

lagging strand

DNA polymerase synthesizes DNA discontinuously, moving away from the replication fork; made up of okazaki fragments

okazaki fragments

found on the lagging strand, joined together by DNA ligase

DNA ligase

joins together okazaki fragments

DNA replisome

protein assemblies that replicate DNA

gene expression

DNA directs protein synthesis by transcription and translation, with proteins being the links between genes and observable traits

telomeres

found on the end of eukaryotic chromosome DNA, used as a buffer to protect the genetic material

telomerase

creates telomeres, makes short buffer sequences when DNA polymerase cannot

mutagen

something or some factor that causes a genetic mutation

thymine dimer

kink in DNA → stalls DNA polymerase/replication → cell death

• caused by UV light exposure

• DNA polymerase can repair the damage if minimal

mismatch repair

one of the jobs of the DNA polymerase is to replace wrong nucleotides in a process called

nucleotide excision repair

one of the jobs of the DNA polymerase is to replace/fix damaged DNA called thymine dimers, in a process called