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Test 3 Flashcards

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Biology 101 flashcards
1
Q

What are the 4 characteristics that genetic material must posses?

A
  1. Must contain complex information
  2. Must replicate faithfully
  3. Must encode the phenotype
  4. Must have the capacity to vary
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2
Q

What is meant by “must contain complex information”?

A

The genetic material must be capable of storing large amounts of information
• instructions for the traits and functions of an organism

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3
Q

What is meant by genetic material “must replicate faithfully”?

A

• At each cell division, genetic instructions must be accurately transmitted to replicated cells.
• When organisms reproduce and pass genes to their progeny, the genetic instructions must be copied faithfully

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4
Q

What is meant by genetic material must “encode the phenotype”?

A

• genetic material has to have capacity to be expressed a a phenotype
• the products of a gene is often a protein or RNA molecule, so there must be a mechanism for genetic instructions in DNA to be copied to RNAs and proteins

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5
Q

What is meant by genetic material must “have the capacity to vary”?

A

• there must be variation with different and within species
• they must differ in their genetic makeup

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6
Q

Why was the discovery of the structure of DNA so important for understanding genetics?

A

understanding how genetic info is encoded and expressed is IMPOSSIBLE without knowing the structure of DNA

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7
Q

What are nucleotides?

A

unit of DNA or RNA

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8
Q

What are nucleotides made of?

A

Sugar, phosphate and a base

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9
Q

What do Chargaffs rules state?

A

Adenine=thymine
Guanine=cytosine

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10
Q

What organism did Fred Griffith use in his experiments?

A

streptococcus pneumoniae TYPES II and III

bacterium that causes pneumonia

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11
Q

What are the variants of the polysaccharide capsule?

A

• Rough
• Smooth

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12
Q

What are the characteristics of the ROUGH (R) variant in S. pneumoniae?

A

• does not form a polysaccharide capsule
• non-virulent
• do not kill mice

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13
Q

What are the characteristics of the SMOOTH (S) variant in S. pneumoniae?

A

• forms a polysaccharide capsule
• virulent
• kills mice

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14
Q

How does the smooth variant kill mice?

A

Because the smooth capsule protects it from the immune system

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15
Q

What happened when Griffith injected heat-killed IIS bacteria?

A

• The mice would live
• no IIIS bacteria in their blood

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16
Q

What happened when Griffith injected living IIR bacteria and a large amount of heat-killed IIS bacteria?

A

The mice got pneumonia and died
• there was IIS bacteria in blood in the heart

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17
Q

What did Griffith conclude?

A

IIR bacteria transformed using the genetic virulence of dead IIS bacteria. This produced a permanent genetic change in the bacteria

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18
Q

What is the transforming principle?

A

DNA; which is the substance responsible for transformation

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19
Q

What did Avery, MacLeod, and McCarty’s experiment reveal?

A

That the transforming substance is DNA

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20
Q

How did Avery, MacLeod, and McCarty do their experiment?

A
  1. Isolated the transforming substance
  2. enzymes that break down proteins had NO effect on the transforming substance
  3. Ribonuclease that destroyed RNA, had no effect
  4. DNase destroyed the transforming substance
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21
Q

What is the conclusion of the Avery, MacLeod, and McCarty experiment?

A

DNA is the carrier of the information for the serotype (type) and capsule (rough or smooth) production

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22
Q

What is a T2 bacteriophage?

A

A virus that infects the bacterium E. coli

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23
Q

How does a a bacteriophage infect a bacterial cell?

A
  1. Attaches to the outer wall of bacterial cell
  2. Injects it’s DNA into cell
  3. Bacterial chromosome break down and phage chromosome replicate
  4. Replicates and directs cell to synthesize phage proteins
  5. Phage DNA becomes encapsulated within the phage proteins
  6. Produce phages that lyse (break open) the cell and escape
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24
Q

What was the purpose of Hershey and Chase experiment?

A

To determine if the phage protein or the phage DNA was transmitted in phage reproduction

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25
Q

Why did Hershey and Chase use isotopes in their experiment?

A

Used as a tracer to identify the location of a specific molecule. A molecule containing the isotope will be radioactive and easily detected

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26
Q

What did Hershey and Chase use to identify and follow phage DNA?

A

• 32P
• phosphorus isotope BECAUSE DNA contains phosphorus

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27
Q

What did Hershey and Chase use to identify and follow phage protein?

A

• 35S
• sulfur isotope because protein contains SULFUR

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28
Q

How did Hershey and Chase do their experiment?

A
  1. One batch contained E. Coli containing 35S and infect bacteria with T2 phage. All progeny phages would have proteins labeled w 35S
  2. Another batch of E. Coli in medium containing 32P and infected bacteria with T2 phage. All progeny phages would have DNA labeled with 32P
  3. Separate batches of unlabeled E. Coli were infected with 35S and 32P labeled progeny phages
  4. After time, they centrifuged the cells to separate proteins from cells
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29
Q

What was the result after centrifuging the 35S batch?

A

• 35S is recovered in the fluid containing the virus coats
• No radioactivity is detected
• protein was not transmitted to the progeny phages

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30
Q

What was the result after centrifuging the 32P batch?

A

• infected bacteria form a pellet containing 32P at the bottom of tube
• progeny phages are radioactive indicating that DNA was transmitted to progeny phages

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31
Q

How did Rosalind Franklin and Wilkins use X-ray diffraction to study DNA?

A
  1. Crystals of a substance are bombarded with X-rays, which are diffracted (bounce off)
  2. The spacing of the atoms within the crystal determines the diffraction pattern, which appears as spots on a photographic film
  3. The diffraction pattern provides information about the structure of the molecule
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32
Q

How did Watson and Crick create the structure of DNA?

A

• used Rosalind’s X-ray diffraction images
• applied the laws of structural chemistry
• used Chargaff’s base ratios

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33
Q

What did Watson and Crick’s model show?

A

• DNA consists of two strands of nucleotides that run in opposite directions
• strands winds around each other to for right-handed helix
• sugars and phosphates on the outside
• bases in the interior

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34
Q

What was the purpose of Fraenkel-Conrat and Singer’s experiment?

A

To figure out if RNA or protein Carrie’s the genetic material in tobacco mosaic virus (TMV)

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35
Q

How did Fraenkel-Conrat and Singer do their experiment?

A
  1. Degraded both types (A and B) of TMV to get RNA and coat proteins
  2. Mix RNA of one type with protein of other type (Type A RNA + type B protein)
  3. Created hybrid viruses
  4. Infect tobacco with the hybrids
  5. New viral particles were produced
  6. New viral progeny were identical to the strain from which the RNA had been isolated and didn’t show strain that donated the protein
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36
Q

What was the conclusion of Fraenkel-Conrat and Singer’s experiment?

A

That RNA directs coat protein synthesis

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37
Q

What did Gierer and Schramm demostrate?

A

RNA isolated from TMV is sufficient to infect tabacco plants and direct the production of new TMV particles

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38
Q

What did Gierer and Schramm confirm?

A

That RNA carries that genetic information in the virus

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39
Q

What are the sugars of nucleic acids?

A

Pentose sugars

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40
Q

How many carbons do pentose sugars have?

A

5

1’, 2’, 3’, 4’, 5’

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41
Q

What is the sugar in RNA?

A

Ribose

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42
Q

What does the ribose have attached at the 2’-carbon?

A

OH

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43
Q

What is DNA’s sugar?

A

DEOXYribose

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44
Q

What does the deoxyribose have attached at the 2’-carbon?

A

One Hydrogen atom

overall contains one oxygen fewer

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45
Q

What are the types of nitrogenous bases?

A

Purine and pyrimidine

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46
Q

What does a purine consist of?

A

A six-member ring attached to a five-member ring

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47
Q

What does a pyrimidine consist of?

A

A six-member ring

48
Q

What are the two purines?

A

Adenine and Guanine

49
Q

What are the three pyrimidines?

A

Cytosine, thymine, and uracil

50
Q

Which purines are present in DNA?

A

Both, adenine and guanine

51
Q

Which purines are present in RNA?

A

Both, Adenine and guanine

52
Q

Which pyrimidines are present in DNA?

A

Only cytosine and thymine

53
Q

Which pyrimidines are present in RNA?

A

Only cytosine and Uracil

54
Q

What is a phosphate group?

A

A phosphorus atom bonded to 4 oxygen atom

55
Q

How do phosphates of nuleic acids respond in near-neutral solvents?

A

Tend to lose H+

56
Q

Where is the phosphate group bonded to on a nucleotide?

A

To the 5’-carbon of the sugar (ribose or deoxyribose)

57
Q

Where do the nitrogenous bases attach to on the sugar?

A

1’carbon of the sugar

58
Q

What are DNA nucleotides called?

A

Deoxyribonucleotides

59
Q

What are RNA nucleotides called?

A

Ribonucleotides

60
Q

How are the sugars in RNA and DNA different?

A

The sugar inRNA has a hydroxyl group (-OH)

61
Q

What is a polynucleotide strand?

A

Series of nucleotides linked together by phosphodiester bonds

62
Q

What is the backbone of the polynucleotide strand composed of?

A

Alternating sugars and phosphate groups

63
Q

How are the complementary bases connected between antiparallel strands?

A

Paired through hydrogen bonding

64
Q

What does the DNA 3’ end consist of?

A

A hydroxyl group attached to the 3’-carbon of the sugar

65
Q

How are DNA nucleotides joined into polynucleotide strands?

A

By phosphodiester bonds connect the 3’-carbon atom of one nucleotide to the 5’-phosphate group to the next

66
Q

What bonds connect sugars and phosphate groups on the same strand?

A

Covalent phosphodiester bonds

67
Q

What is the B form DNA structure?

A

• most common
• most stable
• right-handed helix
• plenty of water surrounds the molecule
• No unusual base sequences in DNA

68
Q

How many base pairs are in each rotation?

A

10 base pairs (3.4nm)

69
Q

What is the A form DNA?

A

• exists if less water is present
• right-handed helix
• shorter and wider
• more turns per distance

70
Q

What is the Z form DNA?

A

• left-handed helix
• sugar-phosphate backbone zigzags back and forth

71
Q

What is the central dogma?

A

How genetic info passes from DNA to protein in a one-way information pathway

72
Q

What are the steps of the central dogma?

A

• DNA replication
• Transcription
• translation

73
Q

What is replication?

A

Information passes from one DNA molecule to other DNA molecules

74
Q

What happens in transcription?

A

Information passes from DNA to RNA

75
Q

What happens in translation?

A

Information passes from RNA to protein

76
Q

What is reverse transcription?

A

Synthesis of DNA from an RNA template

77
Q

What is a hairpin structure?

A

• when sequences of nucleotides on the same strand are complementary and pair with each other

78
Q

What is DNA methylation?

A

when methyl groups are added by enzymes to certain positions on the nitrogenous bases

79
Q

What is supercoiling?

A

Super twisting was a cell compacts DNA

80
Q

What is positive supercoiling?

A

• Overrated DNA
• helix supercoils and twists on itself

81
Q

What is negative supercoiling?

A

• underrotated molecule
• twists on itself in OPPOSITE direction

82
Q

What are looped domains?

A

when DNA is arranged in looped structures and supercoiling will take place within the loops

83
Q

What is chromatin?

A

Complex of DNA and proteins

84
Q

What are histones?

A

•proteins in chromatin
•holds DNA in contact

85
Q

What is formed when DNA is complexed with histones?

A

Nucleosomes

86
Q

What does each nucleosome contain?

A

8 histone proteins around
• 2 copies of each of the core histones

87
Q

What are the four core histones?

A

H2A, H2B, H3, H4

88
Q

How to histones interact with the DNA strand?

A

• positively charge amino acid histone tails INTERACT with negative charge of phosphate on DNA

• keep DNA and histones tightly packed

89
Q

What does the H1 histone do?

A

• Binds to 20-22 bp of DNA where DNA joins
• leaves the histone octamer
• helps lock the DNA into place

•clam around the nucleosome”

90
Q

What is linker DNA?

A

the region of DNA that separates two nucleosomes

91
Q

What is the 10nm chromatin fiber?

A

Lowest level of chromatin structure
• 147-147 bp
• wrapped around histones 1.66 times

92
Q

What is the 30 nm chromatin fiber?

A

• when the the 10nm fiber bundled and condenses
• H1 binds the nucleosome and linker DNA together
• reduces the length of DNA by pulling everything together

93
Q

What are Chromosome Scaffolds?

A

• non histone structural proteins
• 30 nm chromatin fiber emerge in 300 nm loops held by scaffold associated regions (SARs)
• reduces DNA length 10^4 times
• increases width 350-400 times

94
Q

Why are chromosome scaffolds useful?

A

Leaves DNA more accessible when expression is needed

95
Q

What is euchromatin?

A

• condenses and decondenses regionally or regularly
• active gene expression
• where most transcription takes place

96
Q

What is heterochromatin?

A

• highly packed regions of chromosomes
• Doesn’t open up
• fewer active genes
• repetitive sequences
• replicate late in S-phase

97
Q

What is CONSTITUTIVE herterochromatin?

A

• permanent heterochromatin
• found at centromeres and telomeres

98
Q

What is FACULTATIVE heterochromatin?

A

• occur during developmental stages
• these DNA regions can go between heterochromatin and euchromatin at times

99
Q

What does DNase I do?

A

Break the sugar phosphate backbone’s covalent bonds

100
Q

What is the relationship between condensed DNA and DNase I?

A

condensed DNA is bound tightly to proteins and leaves little accessibility to DNase I

101
Q

What is the relationship between decondensed DNA and DNase I?

A

decondensed DNA, 10 nm fiber, and loosely bound DNA in nucleosomes is SUSCEPTIBLE to break by DNase I

102
Q

What is the DNA sequences of centromeres like?

A

They vary widely from species to species
• vary in sequence and length

103
Q

What are common structural features in centromeric chromatin?

A

• heterochromatin (highly condensed)
• in nucleosomes, special histone takes H3 place called CENP-A
• interact with kinetochore proteins

104
Q

What does the kinetochore do?

A

Attached the chromosome to the spindle microtubules

105
Q

What are characteristics of telomeres?

A

• many units of adenine or thymine, followed by guanine units
• tandemly-repeated sequences
• G-rich stand creates a short region of single stranded DNA at the very 3’ end

106
Q

What is a triple-stranded t-loop?

A

• When the G-rich strand folds over and pairs with a short stretch of DNA
• forms a t-loop
• is a protective structure

107
Q

What is shelterin?

A

multipurpose complex that binds to telomeres and protects the end of DNA from being repaid as a double-stranded break in DNA

108
Q

What is unique-sequence DNA?

A

sequences that are present only once or a few times in the genome
• encode proteins for most of the genes

109
Q

What is repetitive-sequence DNA?

A

exists in many copies

110
Q

What is moderately repetitive DNA?

A

• 150-300 bp long
• repeated thousands of times

111
Q

What are interspersed repeats?

A

Repeated sequences that are scattered throughout the genome

112
Q

What are short interspersed elements (SINEs)?

A

• many short repeats
• Alu sequence

113
Q

What is Alu sequence?

A

• 300 bp
• present more than a million times
• 11% of human genome
• no obvious cellular function

114
Q

What are long interspersed elements (LINEs)?

A

• consist of several thousand base pairs

115
Q

What is HIGHLY repetitive DNA?

A

• short sequences
• ~ or > 10 bp
• repeated in tandem and clustered in certain regions of chromosome
• aka satellite DNA
• no known function

116
Q

What is satellite DNA?

A

• aka highly repetitive DNA
• proportions of four bases differ from other DNA sequences
• separates as a satellite fraction when centrifuged

Genetics (11 decks)

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