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Biology > Chapter 9: DNA and It's Role in Heredity > Flashcards

Chapter 9: DNA and It's Role in Heredity Flashcards

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1
Q

Who was Frederick Griffith?

A

a physician trying to find a vaccine for pneumonia

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2
Q

What did Frederick Griffith do?

A

He would heat kill bacterial and inject them into mice to see if the mice would become immune to the pneumonia-causing bacteria

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3
Q

What did Griffith find and how?

A

Found two strains of bacteria but culturing samples from mucus; characterized them as smooth and rough

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4
Q

What strain of pneumonia was dangerous? Why?

A

Smooth (S) was dangerous, rough (R) was not; S strain bacteria had a polysaccharide capsule (which hinders the ability of the immune system to detect them) around their cells and R did not

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5
Q

T/F Chemicals from dead R strains transformed live R cells into virulent S cells

A

F Chemicals from dead S strains transformed live R cells into virulent S cells

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6
Q

What did Avery et al. try to identify?

A

The transforming principle of pneumonia

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7
Q

How did Avery et. al perform their experiments?

A

Treated S bacteria samples to selectively destroy different types of macromolecules

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8
Q

What were Avery et. al hypothesis

A

If macromolecule X is the transforming material, when it is destroyed, the transforming activity will be lost

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9
Q

What did Avery et. al find? What was their conclusion?

A

R strain was still transformed when S-RNA or S-protein was destroyed, but was not transformed if the S-DNA was destroyed

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10
Q

What was Avery et. al conclusion?

A

Because only DNase destroyed the transforming substance, the transforming substance is DNA

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11
Q

In ______, Alfred Hershey and Martha Chase used ________, viruses which attack bacteria, to explore their ideas; What were they trying to determine?

A

1952
Bacteriophage
Determine whether DNA, or protein, is the genetic material

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12
Q

How did Hershey and Chase conduct their experiment

A

they grew cultures of virally infected bacteria with either radioactive phosphate or sulfur. DNA should have the radioactive P and protein would have the radioactive S, so you can see which radiation is transferred to the bacteria

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13
Q

what did Hershey and Chase conclude

A

DNA contained the information needed to make the next generation of phage; the proteins were just there as a package

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14
Q

What is Chargaff’s Rule?

A

DNA molecule has the same amounts of purines and pyrimidines present

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15
Q

What are purines, what are pyrimidines?

A

Purines (Adenine and Guanine)
Pyrimidines (Thymine and Cytosine)

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16
Q

X-ray crystallography showed DNA was a ________

A

right-handed helix of uniform diameter

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17
Q

What can be inferred from the diffraction pattern of X rays passing through the substance?

A

positions of atoms

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18
Q

Who prepared crystallographs of DNA in the early 1950s and what did they discover?

A

Rosalind Franklin
Suggested that DNA is a spiral or helical molecules and that nitrogenous bases are interior

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19
Q

What did Francis Crick and James Watson do?

A

They combined all the knowledge of DNA to determine its structure and built a model

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20
Q

Antiparallel strands

A

The polarity of strand is determined by the sugar-phosphate bonds

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21
Q

What do phosphate groups in DNA connect to?

A

The 3C of one sugar and the 5C of the next sugar

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22
Q

What group is on the 5 end of DNA? What group is on the 3 end?

A

Phosphate on 5
Hydroxyl on 3

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23
Q

In what order is the DNA sequence written for a single strand?

A

5 to 3

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24
Q

What defines the chemical polarity of a strand?

A

Deoxyribose sugar

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25
Q

What causes major and minor grooves?

A

Because of base pairing, the sugar-phosphate backbones are closer together on one side of the double helix

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26
Q

Which groove has atoms more available for hydrogen bonding and protein interaction?

A

major grooves

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27
Q

What is the key to protein-DNA interactions

A

Binding of proteins to specific base-pair sequences

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28
Q

Why do proteins bind to DNA

A

to alter its structure, regulate its transcription or replication

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29
Q

What are the four key structures of DNA structure

A

Double-stranded helix of uniform diameter
Right-handed
Strands are in antiparallel orientation based of 5’ and 3’ carbons
Outer edges of nitrogenous bases are exposed in the major and minor grooves

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30
Q

What are the four important functions of DNA

A

genetic material…
stores genetic information
is suceptible to mutation through a simple alteration in the sequence
is precisely replicated in cell division by complementary base pairing
expressed as the phenotype

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31
Q

Nucleotide sequence dtermines …

A

the sequence of amino acids in protiens

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32
Q

Joined sister chromatids are ___________ that are produced by semi-conservative DNA replication

A

two DNA molecules

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33
Q

Where is there circumstantial evidence for DNA

A

that is present in the nucleus and chromosomes, doubles during the s phase, and there is twice as much in diploid cells as in haploid

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34
Q

DNA amounts…
prior to S phase
following S phase
after Mitosis

A

1 pair of homologous chromosomes
1 pair of replicated homologous chromosomes
2 identical daughter cells

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35
Q

Where are new nucleotides added to a DNA strand

A

At the 3 end

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36
Q

What determines the nucleotide sequence

A

complementary base pairing with the template strand

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37
Q

What direction is the template strand read by DNA polymerase

A

3 -> 5 direction

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38
Q

What does DNA polymerase create?

A

A phosphodiester bond between internal phosphate at 5 carbon and hydroxyl at 3 carbon

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39
Q

What are semiconservative, conservative, and dispersive replication? Which is the way DNA actually replicates

A

semiconservative: each parental strand is a template for a new strand (this is the way it replicates)

conservative: the two parental strands remain together in one daughter molecule while serving as a template for another daughter molecule

dispersive: parent molecule is dispersed among both strands in the two daughter molecules

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40
Q

What did the Meselson-Stahl Experiment do?

A

Grow Ecoli with N15, a heavy isotope that makes DNA denser, then transferred to a medium with N14; discovered that resulting densities could only be explained by the semi-conservative model

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41
Q

What were the results of the Meselson-Stahl Experiment?

A

After one round of replication, DNA had intermediate weight
After subsequent rounds, light-weight DNA and intermediate-weight DNA were present

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42
Q

Why did the data from Meselson-Stahl Experiment provide that DNA replication isn’t conservative or dispersive

A

if conservative, the first generation would have been both high and low density with no intermediate

if dispersive, all the the density of the first gen would have been intermediate, but all future generations would shift closer to being only light

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43
Q

What are the 6 ingredients for PCR

A

DNA template, primers, dNTPs, DNA polymerase, salts and a buffer

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44
Q

What are the three steps to DNA replication

A

Initiation, Elongation, Termination

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45
Q

What happens during the initiation step DNA replication?

A

unwinding (denaturing) the DNA double helix and synthesizing RNA primers

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46
Q

What happens during the elongation step DNA replication?

A

synthesizing new strands of DNA using each of the parental strands as templates

47
Q

What happens during the termination step of DNA replication?

A

synthesis ends

48
Q

What is ori?

A

Origin of replication

49
Q

Where does initiation of DNA replication in prokaryotes occur? How does that impact replication?

A

At a single ori site; one origin of replication means one replication complex per chromosome

50
Q

Initiation in _____ involves many – up to tens of thousands – of ori sites on each chromosome

A

eukaryotes

51
Q

What enzyme separates DNA strands? What does it produce?

A

DNA helicase; it produces a replication fork

52
Q

What does topoisomerase?

A

protects the rest of the DNA molecule from being wound tighter while the strands separate

53
Q

What are single-stranded binding proteins (SSBs)?

A

Keep DNA strands separate during initiation by binding to the single-stranded portions of the DNA

54
Q

Are DNA strands more stable together or separate?

A

Together

55
Q

What gets DNA polymerase to start adding nucleotides?

A

Primase; connects a few complimentary RNA bases to the template strand (RNA primers)

Once RNA primers are in place, DNA polymerase can add DNA bases, copying the template strand

56
Q

Why does DNA copying also proceed in the opposite direction

A

Because it is composed of anti-parallel strands

57
Q

What happens in Elongation

A

Each of the two strands now acts as a template to synthesize a new complimentary strand; new DNA is extended from the primer by DNA polymerase

58
Q

Is the replication fork bidirectional or monodirectional?

A

Bidirectional from origin; leading and lagging strand in both directions

59
Q

What is a replication fork, what happens within in?

A

the site where DNA unwinds to expose bases; the leading strand can grow continuously at its 3’ end as the fork opens, the lagging strand cannot be made this way

60
Q

How is the lagging strand made?

A

Made in Okazaki fragments in the 5 –> 3 direction; cannot begin until the fork has advanced a little ways so it is oriented so that its 3’ end gets farther from the fork

61
Q

What does DNA replication begin with? Which of these is required for the leading strand and each Okazaki fragment?

A

a short primer, RNA complementary to the DNA
RNA is required for the leading strand and each Okazaki fragment

62
Q

What does the enzyme primase do? What happens after it acts?

A

synthesizes the primer RNA on nucleotide at a time; DNA polymerase adds nucleotides to the 3 end of the RNA primer

63
Q

DNA polymerase is ______; what does that mean?

A

processive
catalyzes many polymerizations each time they bind to DNA very rapidly

64
Q

On the lagging strand, synthesis is in the _________ direction to fork movement and requires constant ________

A

opposite
re-priming

65
Q

Synthesis occurs ______ in a series of fragments called ________

A

discontinuously
Okazaki

66
Q

After synthesis of Okazaki fragments…

A

A different DNA polymerase replaces RNA primers with DNA

67
Q

What catalyzes the final phosphodiester linkage between fragments

A

DNA ligase

68
Q

What is termination?

A

the two replication forks meet

69
Q

what happens during termination?

A

The last primer is removed from the lagging strand, no DNA synthesis occurs because there is no 3’ end to extend – a single strand bit of DNA is left at each end (end-replication)

70
Q

What is the problem with end-replication? What is the solution?

A

the new chromosome has a short region of single-stranded DNA overhang at one end, so the chromosome becomes shorter; telomeres

71
Q

What are telomeres?

A

repetitive sequencees (TTAGGG) at the ends of eukaryotic chromosomes; they do not encode proteins

72
Q

What are the functions of telomeres?

A

protect protien-coding DNA from being lost
Extend the chromosome to prevent DNA from being cut off
Prevent DNA repair mechanisms from joining chromosome ends

73
Q

What does Telomerase do? How?

A

adds telomeres back on the end of the chromosome; some; has RNA template that base-pair with the single-strand overhang; works as a DNA polymerase to synthesize new DNA

74
Q

What causes apoptosis? What is it?

A

Too many telomeres are lost, causes cell death

75
Q

Telomers tend to shorten with _____

A

aging

76
Q

In human cells, telomeres are so short after _________ that they die. _____ cells express telomerase

A

30 generations
cancer

77
Q

DNA replication proeeds at a __________ requiring many proteins for distinct patterns of synthesis of ______ and ____ strands

A

replication fork
leading and lagging

78
Q

What does PCR generate and how?

A

generates a large number of copies of a targeted genome region thorough cycles of DNA replication

79
Q

What are mutations?

A

changes of the nucleotide sequence of the genome of an organism

80
Q

What are mutations caused by?

A

any agents that damage DNA; UV light, certain chemicals, viruses, random mistakes

81
Q

What do mutations alter?

A

phenotypes by generating a non-functional protein, changing how a protein works, altering when and where a gene is expressed

82
Q

What are the repair mechanisms for replication mistakes? What enzyme makes these mistake?

A

Proofreading, Mismatch repair, Excision repair
DNA polymerases

83
Q

Proofreading

A

As DNA polymerase adds a nucleotide to a growing strand, it checks if bases are paired incorrectly and fi they are DNA polymerase removes the nucleotide

84
Q

Mismatch repair; what happens if it fails?

A

recognizes old and new strands by modifications present on the template strand; if it fails the DNA sequence may change

85
Q

How are mismatched bases recognized?

A

abnormal hydrogen bonding

86
Q

Point mutation

A

a single base is changed, inserted, or deleted

87
Q

What do mismatches lead to?

A

base-pair substitutions
in some cases the old strand is removed instead of the new

88
Q

Excision Repair

A

Enzymes constantly scan DNA for damaged bases – they are excised and DNA polymerase adds the correct ones

89
Q

How does UV radiation disrupt DNA replication?

A

its absorbed by thymine causing it to form covalent bonds with adjacent nucleotides

90
Q

What are thymine dimers

A

Covalent linkages between adjacent thymines formed on exposure to UV radiation

91
Q

What are spontaneous mutations caused by

A

polymerase errors or spontaneous chemical changes in bases

92
Q

Tautomeric shift

A

Bases have two isomers (tautomers); when a base temporarily forms it’s rare tautomer it can pair with a different base, leading to a mismatch

93
Q

Deamination

A

loss of an NH2 group in cytosine, forming uracil; A will be inserted into the new DNA strand (A pairs with U) instead of G

94
Q

Somatic mutations

A

occur in somatic (body) cells; are not passed to offspring

95
Q

Germ Line Mutations

A

occur in germ line cells (gametes) and are passed to offspring

96
Q

T/F Mutations always affect the phenotype

A

False

97
Q

Silent mutations

A

Do not affect protein function

98
Q

Loss of function mutations

A

prevent gene transcription or produce nonfunctional proteins; nearly always recessive

99
Q

Gain of function mutations

A

lead to a protien with an altered function; usually dominant, common in cancer cells

100
Q

Missense mutation

A

A point mutation in which a single nucleotide change results in a coon that codes for a different amino acied

101
Q

Conditional mutations

A

affect the phenotype only under certain environmental conditions

102
Q

Chromosomal mutations

A

extensive changes in genetic material involving long DNA sequences

103
Q

Why are chromosomal mutations more extensive?

A

It doesn’t affect 1 gene, but 1 chromosome that has hundreds of genes

104
Q

What do chromosomal mutations provide?

A

genetic diversity but can be deleterious

105
Q

What do chromosomal rearrangements involve?

A

double strand breaks

106
Q

What is a cause of chromosomal rearrangements?

A

an aberrant crossover between homologous or nonhomologus chromosomes

107
Q

What does radiation cause?

A

Double strand breaks; repair mechanisms may join non-homologous ends

108
Q

Why will a cell die if there are many chromosome breaks?

A

many pieces are lost of apoptosis is triggered

109
Q

Deletions

A

loss of a chromosome segment; can have severe or fatal consequences

110
Q

Duplications

A

a portion of a chromosome is replicated, resulting in multiple copies

111
Q

Extra copies of genes may lead to _____ of genes

A

overexpression

112
Q

Inversions

A

result from breaking and rejoining, but the segment is flipped resulting in loss-of-function mutations

113
Q

Translocations

A

a segment of DNA breaks off and is inserted into another chromosome; it may involve reciprocal exchanges of chromosome segments

Biology (12 decks)

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