lecture 6 Flashcards
dna replication
what is the process by which a parent cell divides into two daughter cells?
cell division
what are some reasons why cells divide?
- cell size is limited due to the ability to transport food and oxygen from the cell membrane to the interior of the cell
- SA:V; surface area should be bigger
- outside of the cell unable to keep up with what it is trying to contain
what is the process by which genetic information is duplicated?
cell replication
what are the FIVE phases of the cell cycle?
G0: resting phase; cell senescense
G1: growth phase; prepares for DNA synthesis
S: DNA synthesis
G2: growth phase; prepares for mitosis
M: divides into two daughter cells
what replication occurs semi-conservatively. what does that mean?
only half of the parental strand is conserved in the new strand
what model of DNA replication involves both parental strands staying together after DNA replication and the daughter molecules containing all new nucleotides?
conservative model
what model of DNA replication involves the parental and daugther DNA being interspersed in both strands?
dispersive model
what experiment determined that the semi-conservative model was the correct theory for DNA replication?
Meselson-Stahl experiment
what does high fidelity mean?
little to no error
what are the FOUR stages of DNA replication?
initiation, unwinding, primer synthesis, elongation
how is the origin of replication recognized during the initiation stage of DNA replication?
specific sequence of around 250 base pairs, rich in adenine and thymine because they have fewer hydrogen bonds
what do initiator proteins do in DNA replication?
loosens DNA strands and takes the strain off
what enzyme binds to areas of DNA where the strand has been relaxed, thereby reducing torsional strain and causing the unwinding of the double helix?
topoisomerase
what enzyme breaks down hydrogen bonds between complementary nucleotides during the unwinding step of DNA replication?
helicase
what are the purposes of single-strand binding proteins during the unwinding stage of DNA replication?
stabilizes the ssDNA until elongation begins and prevents re-bonding to the parental strand
what is primase and what does it do?
it is a piece of RNA that adds a ribonucleotide primer to ssDNA
what happens to primers after the elongation phase of DNA replication?
they are removed and replaced with DNA nucleotides
what does DNA polymerase do in prokaryotic cells?
they are enzymes that catalyze the attachment of nucleotides to make new DNA during replication
what does DNA polymerase do in eukaryotic cells?
alpha: synthesizes primer
delta: synthesizes leading strand
epsilon: synthesizes lagging strand
what does DNA polymerase require to initiate DNA synthesis?
RNA primer
what is the ONLY direction that DNA polymerase can synthesize DNA in?
5’ to 3’ direction
what is the ONLY direction that DNA is read in?
3’ to 5’ direction
is the sugar-phosphate backbone of DNA hydrophilic or hydrophobic?
hydrophilic - attracts water molecules - polar
what is the molecule that becomes a DNA nucleotide called?
deoxyribonucleotide triphosphate
what end of the nucleotide is the -OH group on?
3’
what end of the nucleotide is the -PO4 phosphate group on?
5’
what is cleaved from incoming dNTP so that it can be attached to the nucleotide strand during the elongation stage of DNA replication?
two phosphates
what type of bond between nucleotides holds together the DNA backbone?
phosphodiester
what is released when a phosphodiester bond is formed?
two phosphate ions
what enzyme joins together newly synthesized DNA strands by creating a covalent phosphodiester bond?
DNA ligase
what is the name of the parts of DNA that are synthesized in chunks on the lagging strand?
Okazaki fragments
what is the name of the enzyme that backs up in the 3’ to 5’ direction to correct replication errors?
exonuclease
what is the complex of repetitive DNA and proteins found at the end of eukaryotic chromosomes called?
telomeres
what does telomerase do?
it replaces the telomere “cap” at the end of the DNA by binding to the overhand using a complimentary RNA primer; synthesizes DNA to make it double stranded; DNA polymerase bonds to this new double stranded segment and fills in the rest as usual
what is cell senescence?
lack of cell division
what is Werner Syndrome?
premature aging caused by cell senescence
what is Bloom Syndrome?
brought on by a mutation in the gene that fixes repairs in the genome, resulting in more chromosome breaks and rearrangements
what is the site of replication called?
replicon
what must be the formed of DNA for it to be replicated?
single stranded
in what direction does replication always occur?
5’ to 3’
