Module 5—The Molecular Basis of Inheritance Flashcards

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1
Q

Friedrich Miescher

A

accidentally isolated DNA for the first time

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2
Q

Albrecht Kossel

A

discovered 4 nitrogenous bases

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3
Q

Phoebus Levene

A

tetranucleotide hypothesis - incorrect belief that the pattern of bases repeated, making DNA unlikely to be the genetic information

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4
Q

Griffith experiment

A

first demonstration of heredity by something abiotic (DNA from dead cells)

combination of dead pathogenic cells with live harmless cells yielded pathogenic cells (“transformation”)

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5
Q

Avery, Macleod & McCarty

A

showed DNA to be the molecule assimilated into a “transformed” cell

destroying DNA prevented transference, but destroying RNA & protein did not

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6
Q

Hershey & Chase

A

showed that DNA is the genetic material

radiolabelled DNA and protein of phage T2; labels showed DNA in E. coli, but not protein

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7
Q

radiolabelling of phage protein

A

radioactive sulfur

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8
Q

radiolabelling of phage DNA

A

radioactive phosphorus

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9
Q

deoxyribose vs ribose

A

ribose has OH groups at 2’ and 3’

deoxyribose has H at 2’ position instead of OH

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10
Q

purines

structure

A

2 rings

adenine & guanine

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11
Q

pyrimidines

structure

A

1 ring

cytosine, thymine, uracil

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12
Q

Chargaff

A

found that base composition of DNA varies between species, but all species have equal ratios of A to T, and C to G

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13
Q

Franklin & Wilkins

A

produced x-ray crystallography images of DNA helical pattern

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14
Q

Watson & Crick

A

deduced structure of DNA:

  • double helix structure
  • double strand
  • complementary base pairing (only A + T and C + G provided uniform width)
  • antiparallel backbones
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15
Q

3 forms of DNA

A

A form

B form

Z form

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16
Q

most important/normal form of DNA

A

B form

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17
Q

2 areas of DNA where base pairs are accessible

A

major & minor grooves

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18
Q

diameter of DNA

A

2 nm

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19
Q

each base is ___ nm apart

A

3.4

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20
Q

DNA makes a complete turn every ___ bases, or every ____ nm

A

10

34

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21
Q

dehydration of DNA produces…

A

A form

no grooves; tighly wound

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22
Q

tension on DNA produces…

A

Z form

left handed

transient

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23
Q

2 DNA strands are linked by…

A

hydrogen bonds between base pairs

24
Q

bonds between stacked base bairs

A

van der waals

25
Q

___ H bonds between A & T

A

2

26
Q

___ H bonds between C & G

A

3

27
Q

correct model of duplication

A

semiconservative

daughter molecule composed of a new one and an old one

28
Q

Meselson & Stahl

A

tested semiconservative model of duplication & found it to be correct

29
Q

location of DNA duplication

A

the replication bubble

30
Q

at the center of the replication bubble

A

origin of replication

31
Q

where two ends of the replication bubble meet

A

replication fork

32
Q

helicase

A

unwinds parental double helix at replication forks

33
Q

single strand binding proteins

A

bind to strand of parental DNA just inside bubble

keep hydrogen bonds from reforming

34
Q

topoisomerase

A

relieves overwinding strain ahead of replication forks (outside of bubble)

breaks, swivels and rejoins strands

35
Q

primase

A

lays down RNA primers at 5’ ends of leading strand and Okazaki fragments

36
Q

DNA pol III

A

synthesizes new DNA strands by adding new nucleotides to the primers

37
Q

DNA pol I

A

removes primers & replaces them with DNA nucleotides

38
Q

DNA ligase

A

joins Okazaki fragments

joins 3’ end of former primer location to the rest of the leading strand

39
Q

DNA polymerization direction

A

5’ → 3’

40
Q

new nucleotides added to…

A

OH group at 3’ location on deoxyribose

41
Q

free nucleotide

structure

bond name

what is released after binding to new strand? purpose?

A

DATP

has 3 phosphates

binds to DNA strand by phosphodiester linkage

pyrophosphate (two PO4) released, providing energy to “pay” for synthesis of large polymer

42
Q

complex of all DNA duplication enzymes

A

DNA replication machine

43
Q

trombone model

A

DNA replication complex is anchored/stationary in the nucleus

DNA is passed through it and duplicated

1 helix enters, 2 helices exit

44
Q

mismatch repair occurs during..

A

duplication

45
Q

steps of mismatch repair

A

enzymes detect mismatched base pairs

nuclease excises damaged segment

DNA pol fills in missing nucleotides correctly

ligase seals the free end (3’)

46
Q

repair enzymes discovered in humans

A

107

47
Q

problem for eukaryotes that prokaryotes do not have

solution

A

duplication leads to degeneration of the ends of chromosomes - loss of genes

telomerases lay down telomeres (RNA templates)

telomeres postpone erosion of chromasomes by providing a buffer region that can safely be lost

48
Q

first level of DNA packing

A

histones

49
Q

help control nucleosome position/packing

A

H1 histones

histone tails

50
Q

organize chromatin into dense loops during division

A

condensins

51
Q

condenses are activated by…

A

mitotic cyclin-cdk complexes

52
Q

period of greatest chromosome density

A

metaphase

53
Q

densely packed chromatin

A

heterochromatin

54
Q

loosely packed chromatin

A

euchromatin

55
Q

suggests order in the organization of the genome during interphase

A

fluorescent labelling