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General Biology 1 > Chapter 14 > Flashcards

Chapter 14 Flashcards

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1
Q

Why did biologists in the early 1900’s think that proteins were the source of genetic information?

A
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2
Q

What is meant by polarity in reference to DNA?

A

Refers to directional orientation of DNA strands. DNA is read in the 5-3 direction and 3-5 direction

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3
Q

What are Chargaff’s rules?

A
  1. Amount of adenine always equals amount of thymine (A = T); amount of guanine always equals cytosine (G = C)

2.

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4
Q

What was Rosalind Franklins contribution to understanding the structure of DNA?

A

Used X-ray crystallography to study 3D structure of DNA

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5
Q

Describe the antiparallel configuration of the double helix.

A
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6
Q

Why is it important that DNA polymerases also have nuclease activity?

A
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7
Q

T or F. Both DNA and RNA polymerases require primers

A

False. Only DNA polymerase requires primers

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8
Q

In what way is DNA replication semidiscontinuous?

A

Replication in leading strand is always continuous; Lagging strand has to be replicated in small chunks - requires many primers

This together makes DNA replication semicontinuous

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9
Q

Why is the lagging strand replicated differently than the leading strand?

A
  • More complicated because its discontinuous
  • Primase is needed to make primers for each Okazaki fragment
  • Okazaki fragments must be stitched together
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10
Q

What is an Okazaki fragment?

A

DNA fragment synthesized on lagging strands

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11
Q

How does the sliding clamp and clamp loader work - what is their function?

A
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12
Q

Why is replication of eukaryotic chromosomes more complicated than prokaryotic? And how do eukaryotic cells overcome these challenges?

A

Eukaryotes:
- multiple replication origins on each chromosome
- multiple, linear chromosomes

Prokaryotes:
- one origin of replication
- singular, circular chromosome

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13
Q

What DNA polymerases are involved in eukaryotic replication? How are they different than those in prokaryotes?

A

DNA pol epsilon - synthesizes leading strand

DNA pol delta - synthesizes the lagging strand

  • Greater division of labor in eukaryotes
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14
Q

Compare specific and non-specific repair mechanisms.

A
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15
Q

What is a thymine dimer, and how are they repaired?

A

Thymine dimer - adjacent thymines become covalently linked

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16
Q

How does excision repair work?

A
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17
Q

A-T base pair

A

Adenine (A) can form two hydrogen bonds with thymine (T)

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18
Q

G-C base pair

A

Guanine (G) can form three hydrogen bonds with cytosine (C)

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19
Q

T or F: Strands are indentical

A

F: Strands are NOT identical; they are COMPLEMENTARY

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20
Q

What are the components of DNA replication?

A

Template – the parent DNA strand

Polymerase enzyme - does the actual ‘copying’

Nucleotides – the building blocks to make the new strand

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21
Q

What are the three stages of DNA replication?

A

Initiation – start of replication

Elongation – where the building blocks are added

Termination – replication ends

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22
Q

DNA polymerase

A

class of enzymes that all synthesize DNA

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23
Q

What are the common features that DNA polymerases share?

A
  • add new bases to 3’ end of existing strands
  • synthesize in 5’-to-3’ direction
  • require a primer of RNA
24
Q

RNA polymerase

A

enzyme that synthesizes primers

25
Q

the origin of replication (oriC)

A

spot on chromosome where replication begins

26
Q

Initiation of DNA replication in prokaryotes begins when:

A
  1. DnaA (protein) binds to oriC
  2. Causes the two strands at this region to separate
  3. Allows the enzymatic machinery for replication to attach to a strand, begin replication
  4. After initiation, replication proceeds bidirectionally –> elongation
27
Q

Nuclease

A

enzyme that breaks down nucleotides

28
Q

Endonuclease

A

enzymes capable of cleaving phosphodiester bonds between nucleotides internally in a DNA strand

29
Q

Exonuclease

A

enzymes capable of cleaving phosphodiester bonds between nucleotides located at the ned of a DNA strand

30
Q

DNA Pol I, II, and II have ________ activity

A

exonuclease

31
Q

DNA polymerase I

A

acts on lagging strand to remover primers and replace them with DNA

32
Q

DNA polymerase II

A

Involved in DNA repair

33
Q

DNA polymerase III

A

Main replication enzyme

34
Q

Helicase

A

enzyme that unwinds DNA (breaks hydrogen binds that hold nucleotides together)

35
Q

T or F: Helicase breaks phosphodiester bonds when unwinding DNA

A

F: Helicase breaks HYDROGEN BONDS

36
Q

Topoisomerase

A

enzyme that relieves torsional strain caused by unwinding

37
Q

DNA gyrase

A

topoisomerase involved in DNA replication

38
Q

Leading strand

A

Continuous strand

39
Q

Lagging strand

A

discontinuous strand

uses multiple primers

40
Q

Replication fork

A

Where DNA synthesis is occurring

41
Q

DNA primase

A

RNA polymerase that makes the necessary primers

42
Q

Primers

A

Short stretched of RNA (10-20 bp)

43
Q

Leading strand synthesis

A
44
Q

Lagging strand synthesis

A

Primase needed to make primers for each Okazaki fragment

DNA Pol I: removes primers and replaces them with DNA

DNA Pol III: synthesizes lagging strand

DNA ligase: Joins Okazaki fragments

45
Q

Replicons

A

areas where replication is occurring on eukaryotic chromosomes

46
Q

DNA pol a (and primase)

A

Involved in priming

47
Q

DNA pol e (epsilon)

A

synthesize leading strand

48
Q

DNA pol d (delta)

A

synthesizes lagging strand

49
Q

Mutagen

A

Agent that induces changes in DNA (mutations)

50
Q

Specific repair

A
51
Q

Nonspecific repair

A
52
Q

Mismatch repair (MMR)

A

removes incorrect bases and replaces them with correct base by copying template strand

53
Q

Thymine dimer

A

Adjacent thymines become covalently linked together

54
Q

What occurs during photorepair

A

UV light causes damage to DNA

Causes thymine dimers

55
Q

Photolyase

A

enzyme that binds to thymine dimers

56
Q

Excision repair

A

Damaged region is removed (excised) then replaced by DNA synthesis

57
Q

What are the three steps in excision repair?

A
  1. Recognition of damage
  2. Removal of damaged region
  3. Synthesis using undamaged strand as template

General Biology 1 (13 decks)

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