Topic 3-2

Question 1

what are the three main differences between eukaryotic and prokaryotic DNA?

Answer 1

• euk. DNA genome is much larger
• euk. DNA is associated with histones
• euk. DNA is linear rather than circular

Question 2

which is faster at synthesizing DNA: eukaryotic DNA polymerase or prokaryotic DNA polymerase

Answer 2

prokaryotic DNA polymerase

Question 3

how do eukaryotes overcome the limits of having slow DNA polymerase?

Answer 3

having multiple sites of origin of replication

Question 4

a unit of replication consisting of DNA independently replicated starting from one origin of replication

Answer 4

replicon

Question 5

how long is a typical replicon?

Answer 5

~200,000 - 300,000 base pairs in length

Question 6

origins of replication in replication in eukaryotes are called:

Answer 6

origin-recognition complex (ORC)

Question 7

during euk. DNA replication, how many times is the genome replicated?

Answer 7

once

Question 8

what is the origin of replication in yeast called?

Answer 8

autonomously replicatin sequences (ARS)

Question 9

during the initiation steps of euk DNA replication, the ORC attaches to each origin of replication with licensing factors to form:

Answer 9

MCM2-7 (minichromosome maintenance) and cofactors

Question 10

MCM2-7 and cofactors at the start of DNA replication form:

Answer 10

active helicase

Question 11

during what stage of the cycle is helicase activated and loaded onto the dsDNA?

Answer 11

S phase

Question 12

what is the difference between DNA helicase in prokaryotes and DNA helicase in eukaryotes?

Answer 12

in prok helicase must be loaded onto ssDNA, but in euk, DNA can be loaded onto dsDNA

Question 13

• has primase activity (synthesizes an RNA primer)
• DNA synthesis activity
  these are characteristics of:

Answer 13

DNA polymerase alpha

Question 14

how long are RNA primers in euk replication?

Answer 14

7-12 nucleotides

Question 15

synthesizes DNA on the lagging strand (euk)

Answer 15

DNA polymerase delta

Question 16

synthesizes DNA on the leading strand (euk)

Answer 16

DNA polymerase epsilon

Question 17

how are euk RNA-DNA primers removed?

Answer 17

unclear

Question 18

stitches okazaki fragments together

Answer 18

DNA ligase

Question 19

how is euk DNA replication terminated?

Answer 19

the replication forks of adjacent bubbles run into each other and the segments of DNA fuse

Question 20

to package the enormous size of euk chromosomes into a cell nucleus, its DNA must be:

Answer 20

highly organized and condensed

Question 21

helps to package DNA

Answer 21

histone proteins

Question 22

the fundamental unit of chromatin (2 tuns of DNA around a histone octamer)

Answer 22

nucleosome

Question 23

creation of nucelosomes requires:

Answer 23

• disruption of original nucleosomes on the parental DNA
• redistribution of preexisting histones on the new DNA
• the addition of newly synthesized histones to complete the formation of new nucleosomes

Question 24

abnormalities in DNA secondary structures are recognized by the:

Answer 24

mismatch repair system

Question 25

what is the end-replication problem in linear DNA?

Answer 25

if you get rid of the RNA primer at the 5' end, there is no way of filling in the gap (no exposed 3'OH)

Question 26

the ends of euk chromosomes, consisting of many repeats of a short sequence of DNA

Answer 26

telomeres

Question 27

an enzyme that elongates the ends of euk chromosomes - reverse transcriptases

Answer 27

telomerase

Question 28

what is reverse transcriptase activity?

Answer 28

synthesizing DNA using an RNA sequence

Question 29

true or false: linear DNA always has an overhanging end

Answer 29

true

Question 30

what is the main function of telomeres?

Answer 30

protects the DNA ends of chromosomes from degradation

Question 31

binds to telomeres and prevents DNA repair mechanisms from recgonizing telomere ends as a double stranded break

Answer 31

shelterin

Question 32

where is telomerase active?

Answer 32

- single celled eukaryotes - germ cells - early embryonic cells - proliferatice somatic cells (like bone marrow)

Question 33

where is telomerase not active?

Answer 33

most somatic cells

Question 34

what happened to the mice that were genetically engineered without telomerase?

Answer 34

they showed signs of premature aging after a few generations

Question 35

- autosomal recessive - mutation in the WRN gene - symptoms of premature aging in adolescence/ adulthood these are characteristics of:

Answer 35

Werner's syndrome

Question 36

what does the WRN gene code for?

Answer 36

telomerase replication

Question 37

what percent of cancer cells express telomerase?

Answer 37

90%

Question 38

expression of telomerase in cancer cells allows them to:

Answer 38

divide indefinitely