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Biol 207 > Topic 3-2 > Flashcards

Topic 3-2 Flashcards

1
Q

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

A
  • euk. DNA genome is much larger
  • euk. DNA is associated with histones
  • euk. DNA is linear rather than circular
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2
Q

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

A

prokaryotic DNA polymerase

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3
Q

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

A

having multiple sites of origin of replication

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4
Q

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

A

replicon

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5
Q

how long is a typical replicon?

A

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

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6
Q

origins of replication in replication in eukaryotes are called:

A

origin-recognition complex (ORC)

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7
Q

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

A

once

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8
Q

what is the origin of replication in yeast called?

A

autonomously replicatin sequences (ARS)

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9
Q

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

A

MCM2-7 (minichromosome maintenance) and cofactors

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10
Q

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

A

active helicase

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11
Q

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

A

S phase

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12
Q

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

A

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

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13
Q
  • has primase activity (synthesizes an RNA primer)
  • DNA synthesis activity
    these are characteristics of:
A

DNA polymerase alpha

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14
Q

how long are RNA primers in euk replication?

A

7-12 nucleotides

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15
Q

synthesizes DNA on the lagging strand (euk)

A

DNA polymerase delta

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16
Q

synthesizes DNA on the leading strand (euk)

A

DNA polymerase epsilon

17
Q

how are euk RNA-DNA primers removed?

A

unclear

18
Q

stitches okazaki fragments together

A

DNA ligase

19
Q

how is euk DNA replication terminated?

A

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

20
Q

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

A

highly organized and condensed

21
Q

helps to package DNA

A

histone proteins

22
Q

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

A

nucleosome

23
Q

creation of nucelosomes requires:

A
  • 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
24
Q

abnormalities in DNA secondary structures are recognized by the:

A

mismatch repair system

25
Q

what is the end-replication problem in linear DNA?

A

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)

26
Q

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

A

telomeres

27
Q

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

A

telomerase

28
Q

what is reverse transcriptase activity?

A

synthesizing DNA using an RNA sequence

29
Q

true or false: linear DNA always has an overhanging end

A

true

30
Q

what is the main function of telomeres?

A

protects the DNA ends of chromosomes from degradation

31
Q

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

A

shelterin

32
Q

where is telomerase active?

A
  • single celled eukaryotes
  • germ cells
  • early embryonic cells
  • proliferatice somatic cells (like bone marrow)
33
Q

where is telomerase not active?

A

most somatic cells

34
Q

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

A

they showed signs of premature aging after a few generations

35
Q
  • autosomal recessive
  • mutation in the WRN gene
  • symptoms of premature aging in adolescence/ adulthood
    these are characteristics of:
A

Werner’s syndrome

36
Q

what does the WRN gene code for?

A

telomerase replication

37
Q

what percent of cancer cells express telomerase?

A

90%

38
Q

expression of telomerase in cancer cells allows them to:

A

divide indefinitely

Biol 207 (34 decks)

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