Flashcards in Lecture--Chapter 13 Deck (85)
DNA strands are _____ and _____.
template strand specifies its complement
DNA strands have a ____ phosphate end and ____ OH end, replication is _____.
5'; 3'; directional
The two DNA strands separate, with each strand used as a template for synthesis of _____.
Replication is _____.
Steps of bacterial replication:
Initiation of DNA replication starts at the ______.
origin of replication (oriC)
site where parental DNA strands have separated and new daughter strands are being made
Elongation and ___ of new DNA.
Replication is _____.
replication forks meet on opposite side of the circle and chromosomes separate
motifs that bind proteins
controls timing of replication
Initiation of DNA replication: _____ initiators, separation of ____ region.
dnaA protein; AT-rich
Initiation of DNA replication: Binding of _____, establishing the _____.
helicase; 2 replication forks
Initiation of DNA replication: ____ and other proteins bind and unwind DNA.
Initiation of DNA replication: ____ generates positive supercoiling ahead of each replication fork.
Initiation of DNA replication: _____ travels ahead of the helicase and relieves positive supercoils.
DNA gyrase (topoisomerase II)
Initiation of DNA replication: ______ bind to the separated strands to keep them apart.
single-strand DNA binding proteins
enzymes that copy DNA
the primary polymerase of replication
DNA polymerase III (DNA Pol III)
has a role in "lagging strand" replication
DNA polymerase I (DNA Pol I)
DNA polymerases are:
1. primer dependent
DNA polymerases: only can add nucleotides to a primer
DNA polymerases: can only synthesise 5' to 3'
DNA polymerases: remain on the strand and catalyse consecutive reactions
___ enters catalytic site
Base pairing according to _____ rule.
A phosphodiester bond forms between:
5'-P of entering dNTP and 3'-OH of the sugar of the previous deoxynucleotide
Outer 2 phosphates of a phosphodiester bond are ____.
occurs at the replication fork
part of elongation: binds to ssDNA, synthesises short complementary RNA strands
part of elongation: complex of helicase, primase, and Pol III.
part of elongation: short, newly synthesised DNA fragments that are formed on the lagging template strand
Elongation: DNA Pol III: On leading strand, moves continuously towards the ____ and covalently bonds the next ____.
replication fork; nucleotide
Elongation: DNA Pol III: On lagging strand, periodically releases the strand, then reforms ____ at replication fork.
Elongation: DNA Pol III: adds ~___ nucleotides per second.
Elongation: DNA Pol I: Removes RNA primers by ____ activity.
Elongation: DNA Pol I: fills in segment with ___
Elongation: DNA Pol I: ____ makes final seal.
Termination: termination sequences on chromosome, opposite oriC.
Termination: proteins bind to ___.
Tus (termination utilisation substance)
Termination: Replication forks stop when they encounter ___.
Termination: ____ dissociates, ____ seals the new strands.
replisome; DNA ligase
2 intertwined DNA molecules
DNA gyrase ___ the molecules.
DNA synthesis has very high ____, 1 error per 108 bases.
Mismatched ___ is unstable.
DNA Pol III has 3' to 5' exonuclease activity
General features of Eukaryotic DNA replication: more complex, though includes many of the same ____.
General features of Eukaryotic DNA replication: Eukaryotic chromosomes are large, linear, and packed in ____.
General features of Eukaryotic DNA replication: Multiple ____ per chromosome.
origins of replication
Numerous polymerases with specialised roles
eukaryotic DNA polymerases
catalyse by-pass segments around damaged DNA
Elongation: removes the RNA primers
Elongation: ___ fills in the gap.
DNA pol delta
repetitive tandem arrays of 12-16 at the ends of chromosomes
Importance of telomeres: The ___ end cannot be otherwise replicated.
Importance of telomeres: Protect the chromosome from ____, ____, or ____.
degradation; fusions; rearrangements
have a 3' overhang at the ends of chromosomes
synthesises telomeres on one strand using its own RNA template
gradually shorten, which limits cellular life-spans
the exchange of DNA between similar or identical segments is found in all species
Homologous recombination is best understood in ____.
In eukaryotes, homologous recombination usually occurs in ____.
Exchange of DNA between non-sister ____ of homologous chromosomes.
Proposed by Robin Holliday in 1964 based on studies of fungi
The Holliday Model
a mobile junction that forms between 4 strands of DNA
The Holliday junction must be ___ to restore duplex DNA.
The Holliday Model: homologous chromosomes align and are ____.
The Holliday Model: a single strand separates from its complementary strand, and basepairs with its complement in the sister chromatid
The Holliday Model: ______ formation between the 4 strands.
The Holliday Model: ____ can continue for some distance along the chromatid and form a ____. This is known as ___.
strand swap; heteroduplex; branch migration
The Holliday Model: eventually another nick may stop the process and the strands are rejoined
The Holliday Model: both chromatids are nicked at _____ locations.
The Holliday Model: The DNA strands to the ___ of the nicks invade the homologous chromosomes and attach to the strands to the ___ of the nicks.
The Holliday Model: The Holliday junction migrates from ___ to ____. This is called ____. It creates 2 ____ regions.
left; right; branch migration; heteroduplex
The Holliday Model: Two heteroduplex regions that have a few base _____.
mismatches (heteroduplex DNA)
Double-Strand Break Model: both backbones are broken in one ___, and some DNA is degraded.
Double-Strand Break Model: ____ uses the other chromatid as a template for replacing lost DNA.
Gap repair function
Double-Strand Break Model: Gap repair function produces 2 _____.
one allele can replace the alternate allele
Gene conversion: DNA ___ repair or DNA ___ repair.
Gene conversion: DNA repair will _______.
correct the mismatches of heteroduplexes