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BIOL 1000 > DNA Replication > Flashcards

DNA Replication Flashcards

1
Q

What is DNA composed of?

A

nucleotides

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2
Q

What are nucleotides composed of?

A

pentose sugar, phosphate group, nitrogenous base

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3
Q

What is the difference in the sugar of DNA and RNA?

A

DNA has deoxyribose sugar (no OH group)

RNA has ribose sugar (has OH group)

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4
Q

What is the difference between purines and pyrimidines?

A

purines are double ring, pyrimidines are single ring

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5
Q

How are nucleotides linked? What type of reaction is this?

A

phosphodiester bonds

condensation

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6
Q

What is the structure of DNA? How are strands arranged?

A

double helix, antiparallel

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7
Q

What is the inside vs the outside of the double helix?

A

inside in nitrogenous bases, outside is sugar phosphate backbone

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8
Q

Why do purines only pair with pyrimidines?

A

because if two purines, not enough room and two pyrimidines, too much room

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9
Q

Is an adenine-thymine bond stronger than a cytosine-guanine bond? Why?

A

No, C-G is stronger

three hydrogen bonds and A-T only has 2

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10
Q

What is antiparallel?

A

5’ end of one strand aligns with 3’ end of other strand of DNA

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11
Q

What is chromatin?

A

mixture of DNA and associated proteins

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12
Q

What are histones?

A

proteins that DNA wrap around in order to fit into the nucleus

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13
Q

What is euchromatin? What does it mean?

A

loosely packed DNA

transcription is occurring (genes are expressed)

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14
Q

What is heterochromatin? What does it mean?

A

tightly packed DNA

transcription is not occurring (genes are not expressed)

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15
Q

What is semiconservative DNA replication mean?

A

each newly made strand is composed of one parent strand (old) and one daughter strand (new)

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16
Q

What are chromosomes?

A

Nuclear units of genetic information that are divided
and distributed by cell division.

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17
Q

Why is replication of DNA important for the cell cycle?

A

ensures that each daughter cells gets the same DNA as parent cell

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18
Q

What is the origin of replication?

A

sequence of DNA (mostly A-T bonds) where replication is initiated

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19
Q

How many times is DNA replicated? Why?

A

once

too much energy, and cells would get too much DNA

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20
Q

What is a replication bubble?

A

area of unwound and open dna

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21
Q

What is a replication fork?

A

ends of the replication bubble where DNA is still in double helix

22
Q

What is helicase?

A

enzyme that unwinds and separates the DNA strands at the Replication Forks

23
Q

What is single strand binding proteins? (SSBS)

A

Proteins that stabilize separated strands by preventing them from rebinding to eachother

24
Q

What is topoisomerase?

A

Relieves twisting pressure on still-wound DNA ahead of the replication fork by making small cuts in the backbone

25
Q

Can DNA polymerase bind anywhere on the template strand?

A

no it needs a starting point (primer)

26
Q

What are RNA primers? What creates them?

A

starting point for DNA polymerase to start building from

primase

27
Q

What is DNA polymerase III? Where does it start from?

A

catalyze the addition of nucleotides to the template strand in a complementary manner

3’ end of RNA primer

28
Q

What direction is DNA created? What direction is parent strand read?

A

5’ to 3’ direction

3’ to 5’ direction

29
Q

What does the sliding clamp of DNA polymerase do?

A

keeps attached to DNA strand until replication is finished

30
Q

What strand does DNA polymerase add bases to?

A

both template strands

31
Q

What are three rules of DNA replication?

A
  1. always elongates from a 3’ end
  2. always add bases in a complementary manner
  3. leading strand, polymerase moves towards fork, lagging strand, polymerase moves away from fork
32
Q

What is the leading strand?

A

elongates towards the replication fork, continuous, only one primer needed, begins from 3’ end of rna primer

33
Q

What is the lagging strand?

A

elongation away from replication fork, not continuous, multiple primers needed, begins from 3’ end of primer

34
Q

What are Okazaki fragments?

A

fragments of dna created on lagging strand

35
Q

What is DNA polymerase I?

A

removes RNA primers and replaces them with DNA nucleotides

36
Q

What attaches okazaki fragments together?

A

DNA ligase by linking the sugar-phosphates (phosphodiester bonds)

37
Q

What happens to eukaryotic DNA after replication? Why?

A

it gets shorter

5’ end of complementary DNA cannot be completed because DNA polymerase
always needs a 3’ end to work from

38
Q

Does DNA loss occur in circular bacterial DNA?

A

no

39
Q

How is gene loss prevented?

A

Non-coding DNA called telomere is at end of DNA (5’TTAGGG3’)

telomeres are removed instead of coding dna

40
Q

What is telomerase? Where is it active? Why?

A

catalyzes the lengthening of telomeres

germ cells (sperm/egg)

these genes are passed to offspring, not as active in somatic cells because they die instead

41
Q

How does telomerase extend?

A

by adding telomere sequence repeats to the 3’ end

Carries an RNA template and has reverse transcriptase activity (RNA to DNA)

42
Q

How is some kinds of cancer linked to telomerase?

A

DNA will not shorten and therefore not die leading to uncontrolled cell division

43
Q

What happens when telomeres get short and eventually coding DNA is not replicated?

A

cell death

44
Q

What are mutations? How are they caused?

A

errors in replication or DNA damage

natural/synthetic chemicals, radioactivity, x-rays, UV

45
Q

What is a thymine dimer?

A

UV light can cause adjacent thymines to bind and create a bend in dna

46
Q

How are mutations avoided during replication?

A

DNA polymerases proofread and repair errors

47
Q

How are mutations fixed after replication occurs?

A

mismatch repair, enzymes identify mismatch, remove it and polymerase replaces it, ligase repairs and joins it to rest of strand

48
Q

What are glycosylases?

A

scan for and recognize specific base alterations

49
Q

What are nucleases?

A

cut the DNA on either side of the error

50
Q

How do repair enzymes know which DNA strand should be cut after replication?

A

original template strand is methylated and has methyl groups attached

new one doesn’t yet

51
Q

What are checkpoints in cell cycle? Why do we have them?

A

where it is checked that everything occurred properly and nothing is damaged

do not want to pass on incorrect DNA to daughter cells

BIOL 1000 (12 decks)

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