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Biology > Packet flashcards > Flashcards

Packet flashcards

1
Q

Chromosomes

A

Complex of DNA and proteins

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2
Q

Genes

A

Made of DNA and act as instructions to make proteins

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3
Q

2 major features of DNA

A

The backbone made of sugar and phosphate groups.

Series of bases that project from each sugar in the backbone

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4
Q

Hershey-Chase Experiment

A

Studied how the T2 virus infects and replicates in the bacterium Escherichia coli

T2 infection of E. coli begins when:
The virus injects its genes into the cell and they direct the production of new virus particles.

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5
Q

What was the conclusion of the Hershey-Chase experiment

A

DNA can replicate

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6
Q

Structure of DNA

A

Double-stranded
Each strand consists of deoxyribonucleotides (deoxyyribose sugar, phasphate group, and nitrogenous base)

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7
Q

Phosphodiester linkage

A

Covalent bond
The hydroxyl group on 3’ carbon of one deoxyribose joined by a covalent bond to the phosphate group attached to 5’ carbon of another deoxyribose.

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8
Q

DNA directionality

A

5’ to 3’ direction

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9
Q

Semiconservative replication

A

Parental strands separate and each is template for a new daughter strand.

Each daughter has one old and new strand.

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10
Q

Conservative replication

A

The parental molecule serves as an entirely new molecule.

One daughter has both old strands; other has both new strands.

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11
Q

Dispersive replication

A

Parent molecule is cut into small pieces

Each daughter has an old and new DNA interspersed.

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12
Q

What did Watson and Crick propose

A

Proposed existing DNA strands of DNA served as a template.
Deoxyribonucleotides were added to new strands according to complementary base pairings.

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13
Q

Meselson-Stahl Experiment

A

Experiment done by Mehselson and Stahl that demonstrated that DNA replicated semi-conservatively.

Grew bacteria in a heavy isotope of Nitrogen (15N), then transferred to light nitrogen. Put in medium and spun.

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14
Q

DNA Polymersase

A

Enzyme that catalyzes DNA synthesis

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15
Q

What direction does DNA synthesis proceed

A

It only works in one direction which means the 5’ –> 3’ direction

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16
Q

Origin of replication

A

Sequence of bases on a chromosome where DNA replication starts

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17
Q

How many origin of replications are in bacterial chromosomes

A

1

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18
Q

How many origins of replications are there in eukaryotes

A

Multiple orgins of replication along each chromosome

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19
Q

What forms as DNA is synthesized

A

Replication bubble

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20
Q

Where do replication bubbles form

A

specific sequence of bases called the origin of replication.

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21
Q

Where does active DNA synthesis take place?

A

Replication forks of each replication bubble

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22
Q

DNA helicase

A

Protein that breaks hydrogen bonds between two DNA strands to separate them

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23
Q

Single-strand DNA-binding proteins

A

Attach to separating strands of DNA during replication. It prevents them from reforming the double helix

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24
Q

Topoisomerase

A

An enzyme that unwinds DNA double helix

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25
Q

3 limitations of DNA polymerases

A
  1. Can only synthesize DNA in the 5’–> 3’ direction
  2. DNA polymerases cannot start synthesis from scratch on a template strand
  3. DNA polymerases can only extend from the 3’ end of an existing strand that is hydrogen-bonded by complementary base pairings to the template
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26
Q

Primer

A

a short nucleic acid sequence that provides a starting point for DNA synthesis

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27
Q

Primase

A

An enzyme that synthesizes a short stretch of RNA to use as a primer during DNA replication

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28
Q

RNA polymerase

A

Enzyme that synthesizes RNA molecules from a DNA template through transcription

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29
Q

Difference between RNA and DNA polymerase

A

RNA polymerase can start synthesis from scratch

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30
Q

Leading strand

A

Strand of DNA that is synthesized towards the replication fork

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31
Q

Lagging strand

A

Strand synthesized away from the replication fork

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32
Q

Discontinuous replication hypothesis

A

Proposed to explain how the lagging strand is synthesized.

Held that primase synthesizes new RNA primers for lagging strands, and that DNA polymerase synthesizes short DNA fragments from these primers

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33
Q

Ozaki fragments

A

Short segments of DNA produced during replication of lagging strand template

Okazaki fragments are eventually linked together to produce the lagging strand in newly synthesized DNA

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34
Q

Synthesis of lagging strand

A

Priming: The lagging strand is synthesized in the 3’ to 5’ direction, which is opposite to the direction of the DNA replication fork. To initiate synthesis, an RNA primer is synthesized by the enzyme primase.

Initiation of Okazaki Fragment: DNA polymerase III adds nucleotides to the RNA primer, synthesizing a short DNA fragment called an Okazaki fragment. This process is initiated at the RNA primer.

Extension of Okazaki Fragment: DNA polymerase III continues to add nucleotides, extending the Okazaki fragment in the 5’ to 3’ direction.

Removal of RNA Primer: The RNA primer of each Okazaki fragment is removed by the enzyme RNase H, leaving a gap.

Fill-in by DNA Polymerase I: The gap left after primer removal is filled in by DNA polymerase I. This enzyme has both 5’ to 3’ polymerase activity and 5’ to 3’ exonuclease activity.

Ligation: DNA ligase seals the nick between adjacent Okazaki fragments by catalyzing the formation of a phosphodiester bond, producing a continuous lagging strand.

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35
Q

DNA ligase

A

An enzyme that joins pieces of DNA by catalyzing the formation of a phosphodiester linkage between the pieces.

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36
Q

DNA polymerase III

A

Extends leading strand and creates okazaki fragments by extension of RNA primers

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37
Q

Sliding clamp

A

Holds DNA polymerase in place during strand extension

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38
Q

Replisome

A

macromolecular machine that copies DNA; includes DNA polymerase, helicase, primase, and other enzymes

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39
Q

Telomeres

A

Region at the end of the eukaroyitc chromosome

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40
Q

Problem with copying telomeres

A

The lagging strands become too short as an enzyme that degrades the ribonucleotides removes the primer. As a result the single-strand DNA remains single stranded

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41
Q

Telomerase

A

Enzyme that adds DNA to the ends of chromosomes (telomeres) to prevent them being shortened by DNA synthesis

42
Q

Where are telomerase found and not found

A

Found in gametes and stem cells and are not found in somatic cells

43
Q

What happens to chromosomes of somatic cells without telomerase

A

Gradually shortens with every mitotic division and becomes shorter as an individual ages

44
Q

Dark side of telomere

A

Cancer cells have active telomerase that allow unlimited division of cancer cells

45
Q

How accurate is DNA synthesis

A

Very accurate as, it only inserts an incorrect base once every 100,000 bases

46
Q

What happens to incorrect bases

A

Repair enzymes remove defective bases and replace them with the correct one

47
Q

Two sources of where DNA polymerase’s ability to select correct deoxyribonucleotide to add to a growing strand

A
  1. Correct base pairs are energetically favorable
  2. Shape of an incorrect base pairs differs from correct ones
48
Q

Proofreading

A

Process where DNA polymerases “check their work,” fixing the majority of mispaired bases.

49
Q

Exnuclease active site

A

Mismatched deoxyribonucletidfe moves to site where it does fit and the site catelazyes removal of incorect ribonucleotide

50
Q

Mismatch repair enzymes

A

Recognizes mismatched pairs, incorrect base and fills in correct bases.

51
Q

Nucleotide excision repair

A

DNA repair that removes damaged regions in one strand of DNA and replaces it with a correct seqence using the undamaged strand as a template.

52
Q

Xeroderma pigmentosum

A

Rare autosomal recessive disease in humans
Causes extreme sensitivity to UV light that increases chances of skin cancer

53
Q

Gene expression

A

Process of converting information in DNA into functioning molecules within the cell

54
Q

one-gene, one-enzyme hypothesis

A

Each gene contains information to make an enzyme

55
Q

Mutant

A

modification of the gene to make it different

56
Q

Genetic Code Hypothesis

A

Sequence of bases in DNA acted as a code

57
Q

Messenger RNA

A

Intermediatary between genes and proteins that carries info from DNA to site of protein synthesis

58
Q

RNA polymerase

A

Catalyzes synthesis of RNA from ribonucleotides using a template usually consisting of DNA

59
Q

Central dogma

A

DNA codes for RNA, which codes for proteins

60
Q

Transcription

A

the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA)

61
Q

Translation

A

process of using information in mRNA to synthesize proteins

62
Q

Organism’s genotype

A

Determined by sequences of bases in DNA

63
Q

Organism’s phenotype

A

Product of proteins it produces

64
Q

Reverse transcriptase

A

An enzyme that can synthesize DNA from an RNA template

65
Q

genetic code

A

speicfies how a sequence of nucleotides code for a sequence of amino acids

66
Q

triplet code

A

shortest genetic word to code for at least 20 amino acids

67
Q

Codon

A

Group of three bases that specifies a particular amino acid

68
Q

Reading frame

A

Sequence of codons that could be destroyed by adding or subtracting one or two bases

69
Q

Mutation

A

PERMANENT CHANGE TO DNA BULLSHITTER

70
Q

Point mutations

A

Result from one or small number of base changes

71
Q

Chromosome-level mutations

A

larger in scale

72
Q

Missense mutations

A

Change an amino acid in protein

73
Q

Silent mutation

A

A point mutation that changes the sequence of a codon without changing the amino acid that is specified

74
Q

Frameshift mutations

A

The addition or deletion of one or a few base pairs in a coding sequence that shifts the reading frame of the mRNA

75
Q

nonsense mutation

A

Change codon that specifies an amino acid into stop codon

76
Q

Beneficial mutations

A

Increase fitness (ability to survive and reproduce) of an organism

77
Q

Neutral mutations

A

Do not affect an organism’s fitness

78
Q

Deleterious mutations

A

Decreases the fitness of an organism

79
Q

Chromosome mutations

A

May change chromosome number (polyploidy and aneuploidy) or structure

80
Q

Four types of chromosome structural mutations

A

Deletion
Inversion
Duplication
Translocation

81
Q

Inversion

A

Segment of chromosome breaks off, flips around, and rejoins

82
Q

Deletion

A

Segment of a chromosome is lost

83
Q

Duplication

A

segment of chromosome is present in multiple copies

84
Q

Translocation

A

Section of chromosome breaks off and becomes attached to another chromosome

85
Q

Karyotype

A

Complete set of chromosome in cell

86
Q

Genetic code is

A

Redundant: All but two amino acids are encoded by more than one codon
Unambiguous: One codon never codes for more than one amino acid
Non-overlapping: Codons are read one at a time
Universal: All codons specify the same amino acids in all organisms
Conservative: If several codons specify the same amino acid, the first two bases are usually identical

87
Q

Initiation

A

the first phase of transcription in bacteria where sigma protein must bind to the core enzyme to recognize sites where transcription should begin

88
Q

Promoters

A

The sites that sima recognizes where transcription begins

89
Q

sigma

A

Protein that binds to the core enzmye to recognize sites where transcription begins

90
Q

Core enzyme

A

general term for the enzyme within a multipart holoenzyme that is responsible for catalysis

91
Q

holoenzyme

A

What RNA polymerase core enzyme and sigma form

92
Q

What is the core enzyme for bacteria

A

bacterial RNA polymerase

93
Q

How many base pairs long are promoters

A

40-50 pairs long and had a series of bases on one strand of DNA identical or similar to TATAAT

94
Q

-10 box

A

Six base pair sequence known as -10 box as it is centered 10 bases from the point where transcription starts

95
Q

Downstream

A

Direction in which RNA polymerase moves along a DNA strand

96
Q

Process: Initiating transcription in bacteria

A
  1. Initiation begins, sigma binds to promoter region of DNA
  2. Initiation continues, RNA polymerase opens the DNA helix and transcription begins
  3. Initiation is complete: Sigma is released from the core enzyme; RNA synthesis continues from DNA
96
Q

Upstream

A

Opposite to the direction in which RNA polymerase moves along a DNA strand

97
Q

Elongation

A

Process by which RNA lengthens during transcriptions as nucleotides are added to the 3’ end of the RNA

98
Q

Termination

A

Ends transcription when RNA polymerase transcriptes a DNA sequence called a transcription-termination signal
Causes the RNA polymerase to separate from the RNA transcript

99
Q

Process: One way of ending transcription in bacteria

A

Hairpin forms
RNA polymerase transcribes a trranscription terminal signal, which codes for RNA that forms a hairpin

Termination
If a hairpin is followed by a stretch of U nucleotides in the RNA, this leads to the RNA separating from RNA polymerase terminating transcription

Biology (40 decks)

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