lecture 6

Question 1

what is the process by which a parent cell divides into two daughter cells?

Answer 1

cell division

Question 2

what are some reasons why cells divide?

Answer 2

• 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

Question 3

what is the process by which genetic information is duplicated?

Answer 3

cell replication

Question 4

what are the FIVE phases of the cell cycle?

Answer 4

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

Question 5

what replication occurs semi-conservatively. what does that mean?

Answer 5

only half of the parental strand is conserved in the new strand

Question 6

what model of DNA replication involves both parental strands staying together after DNA replication and the daughter molecules containing all new nucleotides?

Answer 6

conservative model

Question 7

what model of DNA replication involves the parental and daugther DNA being interspersed in both strands?

Answer 7

dispersive model

Question 8

what experiment determined that the semi-conservative model was the correct theory for DNA replication?

Answer 8

Meselson-Stahl experiment

Question 9

what does high fidelity mean?

Answer 9

little to no error

Question 10

what are the FOUR stages of DNA replication?

Answer 10

initiation, unwinding, primer synthesis, elongation

Question 11

how is the origin of replication recognized during the initiation stage of DNA replication?

Answer 11

specific sequence of around 250 base pairs, rich in adenine and thymine because they have fewer hydrogen bonds

Question 12

what do initiator proteins do in DNA replication?

Answer 12

loosens DNA strands and takes the strain off

Question 13

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?

Answer 13

topoisomerase

Question 14

what enzyme breaks down hydrogen bonds between complementary nucleotides during the unwinding step of DNA replication?

Answer 14

helicase

Question 15

what are the purposes of single-strand binding proteins during the unwinding stage of DNA replication?

Answer 15

stabilizes the ssDNA until elongation begins and prevents re-bonding to the parental strand

Question 16

what is primase and what does it do?

Answer 16

it is a piece of RNA that adds a ribonucleotide primer to ssDNA

Question 17

what happens to primers after the elongation phase of DNA replication?

Answer 17

they are removed and replaced with DNA nucleotides

Question 18

what does DNA polymerase do in prokaryotic cells?

Answer 18

they are enzymes that catalyze the attachment of nucleotides to make new DNA during replication

Question 19

what does DNA polymerase do in eukaryotic cells?

Answer 19

alpha: synthesizes primer
delta: synthesizes leading strand
epsilon: synthesizes lagging strand

Question 20

what does DNA polymerase require to initiate DNA synthesis?

Answer 20

RNA primer

Question 21

what is the ONLY direction that DNA polymerase can synthesize DNA in?

Answer 21

5’ to 3’ direction

Question 22

what is the ONLY direction that DNA is read in?

Answer 22

3’ to 5’ direction

Question 23

is the sugar-phosphate backbone of DNA hydrophilic or hydrophobic?

Answer 23

hydrophilic - attracts water molecules - polar

Question 24

what is the molecule that becomes a DNA nucleotide called?

Answer 24

deoxyribonucleotide triphosphate

Question 25

what end of the nucleotide is the -OH group on?

Answer 25

3’

Question 26

what end of the nucleotide is the -PO4 phosphate group on?

Answer 26

5’

Question 27

what is cleaved from incoming dNTP so that it can be attached to the nucleotide strand during the elongation stage of DNA replication?

Answer 27

two phosphates

Question 28

what type of bond between nucleotides holds together the DNA backbone?

Answer 28

phosphodiester

Question 29

what is released when a phosphodiester bond is formed?

Answer 29

two phosphate ions

Question 30

what enzyme joins together newly synthesized DNA strands by creating a covalent phosphodiester bond?

Answer 30

DNA ligase

Question 31

what is the name of the parts of DNA that are synthesized in chunks on the lagging strand?

Answer 31

Okazaki fragments

Question 32

what is the name of the enzyme that backs up in the 3’ to 5’ direction to correct replication errors?

Answer 32

exonuclease

Question 33

what is the complex of repetitive DNA and proteins found at the end of eukaryotic chromosomes called?

Answer 33

telomeres

Question 34

what does telomerase do?

Answer 34

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

Question 35

what is cell senescence?

Answer 35

lack of cell division

Question 36

what is Werner Syndrome?

Answer 36

premature aging caused by cell senescence

Question 37

what is Bloom Syndrome?

Answer 37

brought on by a mutation in the gene that fixes repairs in the genome, resulting in more chromosome breaks and rearrangements

Question 38

what is the site of replication called?

Answer 38

replicon

Question 39

what must be the formed of DNA for it to be replicated?

Answer 39

single stranded

Question 40

in what direction does replication always occur?

Answer 40

5’ to 3’