Final (ch 20) Flashcards
The 3’-5’ exonuclease activity of E.coli DNA polymerase III accounts for this of polymerization
low error rate
An okazaki fragment is
small segment of DNA that is an intermediate in the synthesis of the lagging strand
what effect does topoisomerases have upon DNA
changes the supercoiling of DNA
Replication of eukaryotic DNA must be this
controlled to coordinate with the cell cycle
single strand binding proteins are important for preventing this
single stranded DNA from rewinding and protecting it from degradation
in most organisms replication proceeds in this mannor from here
bidirectional
replication origin
An E.coli has this many replication forks on ints ingle chromosome: humans have this many replication forks on each chromosome
2
many
These attack ssDNA
nucleases
3 features of NDA replication
semiconservative
bidirectional
semi-discontinuous
what does semi discontinuous mean
leading strand copies continuously
lagging strand copies in segments which must be joined
DNA molecules are supercoiled in this mannor in vivo
negatively
why are they negatively supercoiled
helps replication machinery gain access to the two template strands
which phase is DNA replicated in
S
Which phase has rapid grown and metabolic activity
G1
which phase has grown and preparation for cell division
G2
How long to replicate DNA in eukaryotes
8 hours
This alters DNA supercoiling
topoisomerases
this is the site where DNA strands separate and new strands are synthesized
replication fork
Bacterial DNA replication is done in this mannor
bidirectional
this is the machinery for replication in bacterial DNA
replisome
how long to duplicate E.coli dna
38 min
convert dsDNA to ssDNA
helicase
binds ssDNA
single-stranded binding protein
makes RNA primers
primase
extends the new chain through polymerization of dNTP’s
DNA polymerase
removes the RNA primer
Rnase
joins the two DNA (Okazaki) fragments
DNA ligase
anti parallel strands of dna are replicated simultaneously
T
DNA can only extend a prexisting chain
T
RNA primers are this long
10-60 nucleoties long
involved in repairing and patching DNA, single polypeptied chain
DNA polymerase I
strictly a repair enzyme, multi subunits
DNA polymerase II
major DNA replication enzyme, responsable for chain elongation
DNA polymerase III
This strand is formed semidiscontinuously
lagging strand
This is the leading most compound in DNA synth
DNA gyrase
How often does DNA polymerase make an error
only once in ever 10^9 ro 10^10
This compound does both proofreading and repair functions
DNA polymerase I
Cut and patch process
nick translation
Discontinuous segments of the lagging strand are joined by this, requiring hydrolysis of high energy bonds
ligase
This repeatedly adds nucleotides to the 3’ end of DNA called this
telomerase
telomeres
an alteration in a cell’s DNA is call a
mutation
cells with badly damaged DNA are susceptible to this
apoptosis
cells with damaged DNA that excape normal growth-control and proliferate excessively often result in this
cancer
only macromolecule that can be repaired
DNA
Lesions may be fixed by this which does not require breaking the phosphodiester backbone of DNA
direct repair
These are common culprits for DNA damage
reactive oxygen species
nucleotide substitution is this
point mutation
changing a purine to a different purine or pyrimidine to a different pyrimidine
transition mutation
chaning a purine to a pyriumidine or vice versa
transverse mutation
DNA base is removed
Abasic mutation
These can also alter base identity
deamination
This can remove meythl groups from DNA bases
methyltranferase
a damaged base is excised from sugar-phosphate back bone by this (most common DNA lesion)
DNA glycosylase
Recombination can do this
restore broken DNA molecules by splicing two peices of DNA together
