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Genetics Term 1 > Genes > Flashcards

Genes Flashcards

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1
Q

What are Chargaff’s Rules?

A
  1. # of A = # T (same for C&G)

2. # of A + T and C+G are equal on both strands

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2
Q

What is azidothymidine? (Zidovudine)

A
  • Anti-Viral Drug
  • Incorperation of nucleotiees that lack 3’-OH
  • Used to treat HIV
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3
Q

Why doesn’t azidothymidine hurt humans?

A
  • Human polymerase prefers Thymidien

- Viral Polymeraase prefers azidothymidine (AZT)

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4
Q

What is methylated in DNA?

A
  • A & C nucleotides

- Histones

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5
Q

What keeps the two strands of DNA separate during replication?

A

-Single-stranded DNA binding proteins

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6
Q

What replaces the RNA primer in DNA replication?

A

-DNA polymerase I

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7
Q

What is Gyrase?

A

-The bacterial equivalent to topoisomerase

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8
Q

What drug targets Gyrase?

A

-Floroquinolones

Ciprofloxacin

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9
Q

How do Floroquinolones work?

A

Inhibit bacterial gyrase, causeing cell death

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10
Q

How does a cell identify DNA damage?

A

Repair enzymes continuously scan DNA strands for alterations in Tertiary structure of DNA or bulges, nicks in the phosphodiester bonds of the backbone, loops, double stranded breaks

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11
Q

Which enzymes are involved in DNA repair?

A
  • Nucleases remove the damaged region
  • DNA polymerase replaces the nucleotides
  • DNA ligase seals the PDE bond
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12
Q

What is the role of p53 in DNA repair?

A
  • It stops DNA replication until DNA is repaired
  • Activates/sustains DNA Repair complexes
  • Induces apoptosis if DNA Repair is not possilbe
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13
Q

What is a genetic disorder in which the DNA repair enzymes are damaged?

A

Xeroderma pigmentosum

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14
Q

How does Ionizing radiation damage DNA?

A

It affects sugar-phosphate backbone, leading to strand breaks-It damages purine rings

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15
Q

How does UV light damage DNA?

A

Causes dimerization between adjacent C and T bases

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16
Q

How do repair enzymes know which strand of DNA is the parent strand?

A

The parent strand is usually more methylated

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17
Q

What’s the difference between Exonucleases and Endonucleases?

A
  • Exonucleases cleave 1 nucleotide from the end of a strand

- Endnonucleases cleave DNA at the middle of the strand

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18
Q

What enzyme is used to treat Cystic Fibrosis?

A

Dornase

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19
Q

What is homologous recombination?

A

The crhomosomal copy serves as a template so that its homologue can be repaired

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20
Q

Which type of cells contain telomerase?

A

Stem cells

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21
Q

What happens if a mature cell acquires telomerase?

A

Cancer

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22
Q

What is senescence?

A

Biological aging. Since DNA damage cannot be repaired, the cell stops dividing. The cell will go through apoptosis or will be eliminated by the immune system

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23
Q

What is the Hayflick Limit?

A

The point at which a cell can no longer divide, happens after ~50 divisions.

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24
Q

Why is RNA less stable than DNA?

A
  • Single Stranded

- 2’ OH makes RNA more prone to hydrolysis

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25
Q

What does it mean for a gene to be polycistronic?

A

It codes for multiple proteins

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26
Q

Which strand is the “Sense” strand?

A

The 5’-3’ DNA strand

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27
Q

Which strand is the “Antisense” strand?

A

The 3’-5’ DNA strand

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28
Q

In what direction is RNA synthesized?

A

5’-3’

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29
Q

Which DNA strand serves as a template for RNA polymerase?

A

The Antisense strand

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30
Q

What makes up the core promoter of Prokaryotes?

A

TATA box and -35 sequence

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31
Q

What does the prokaryotic transcription promoter strength depend on?

A

The exact sequence and distance between the promotors

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32
Q

When are prokaryotic Upstream elements necessary?

A

For highly expressed genes

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33
Q

What do Prokaryotic upstream elements do?

A

serve as additional binding sites for RNA polymerase

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34
Q

What does the operator sequence of the operon do?

A

Serves as a binding site for a repressor or activator

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35
Q

What is the promotor sequence of eukaryotes for?

A

Binding spot for Transcription factors. RNA polymerase cannot bind directly to the strand.

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36
Q

What does RNA polymerase bind to in eukaryotic cells?

A

The transcription factors

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37
Q

What are 2 examples of transcription factors in eukaryotes?

A
  • Steroids

- NF-kB

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38
Q

Why shouldn’t steroids that are being administered to a patient be stopped abruptly?

A

dose should be gradually lowered to facilitate return to normal gene expression

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39
Q

What is NF-kB?

A
  • Eukaryotic transcription factor

- Regulates many immune-related proteins

40
Q

Where are eukaryotic enhancer regions located? What is their purpose?

A
  • 5’ region upstream of the promoter, and 3’ region downstream of the transcription termination site
  • Purpose is to serve as binding sites for insulator proteins that shield from influences of adjacent genes
41
Q

How are Eukaryotic genes inactivated?

A
  • DNA and histones are methylated by DNA methyltransferase

- histones are De-acetylated by histone deacetylase (HDAC)

42
Q

How are Eukaryotic genes activated?

A
  • DNA and histones are De-methylated

- histones are acetylated

43
Q

What do the 3 eukaryotic RNA polymerases do?

A

Produce:
I: rRNA
II: mRNA
III: tRNA

44
Q

What ions are required for the function of RNA Polymerse?

A

Mg2+ and Mn2+

45
Q

Does RNA polymerase require a primer?

A

No

46
Q

How does RNA polymerase initiate transcription?

A

It loosely slides along DNA until it reaches a promoter sequence and/or transcription factors through its sigma unit

47
Q

What sequence of DNA signals the stop of transcription?

A

a GC-rich region followed by an AT-rich region

48
Q

What do release factors do?

A

Bind to new RNA and pull it away from RNA polymerase and the DNA template

49
Q

What are two antibiotic examples, and one poison example of RNA polymerase inhibitors?

A

Antibiotic: Rifampin & ActinomycinPoison: Amanitin

50
Q

Rifampin

A
  • Inhibits initiation of RNA transcription in bacteria

- Used in Tuberculosis therapy

51
Q

Actinomycin

A
  • antibiotic
  • Inhibits elongation
  • Used in cancer therapy
52
Q

Amanitin

A

poison from mushrooms-Inhibits human RNA polymerase II elongation

53
Q

What is the 5’ end of eukaryotic RNA capped?

A

With methylguanosine triphosphate

54
Q

What is the purpose of the 5’ RNA cap?

A
  • necessary for ribosome binding

- Protects 5’ end

55
Q

What is the purpose of the 3’ RNA Poly(A)-tail?

A
  • Protect 3’ end-Stabilize RNA

- Regulates the half-life of mRNA

56
Q

What is alternate splicing?

A

different combinations of exons from the same gene. One gene, different mature proteins

57
Q

What is trans-splicing?

A

splicing of exons from two different pre-mRNA’s. Only occurs in lower eukaryotes.

58
Q

What does it mean for the genetic code to be degenerative?

A

There can be more than 1 codon code for 1 amino acid

59
Q

What is the genetic cause of Huntington’s Disease?

A

Several CAG triplets inserted into the gene for huntingtin. No shift of reading frame.

60
Q

Before the ribosome attaches to mRNA, the mRNA must be ______

A

Activated by ATP, forming an aminoacyl-AMP

61
Q

What does the wobble hypothesis say?

A

The anti codon only really has to match the first two nucleotides of the mRNA. The 5’ nucleotide of the tRNA has more freedom in match

62
Q

In what direction are proteins made?

A

Amino-to-carboxyl direction

63
Q

Why is it that protein synthesis has no proof-reading steps?

A

Speed is more important than perfection-Incorrect proteins will rapidly be degraded

64
Q

Outline the steps of mRNA export from the nucleus

A
  1. mRNA stabilized by nuclear RNA-Binding proteins
  2. React with nuclear pore receptors to open pore
  3. Once in cytosol, replaced by cytosolic RNA binding proteins
65
Q

What is required for prokaryotic mRNA translation to initiate?

A

Shine-Dalgarno sequence upstream of the start codon-start codon (AUG)

66
Q

What is required for eukaryotic mRNA translation to begin?

A
  • 5’ caps

- Start codon after 5’cap

67
Q

What is the Shine-Dalgarno sequence?

A

a purine-rich sequence upstream of the start codon required for prokaryotic protein synthesis

68
Q

Why is it important that the start codon in prokaryotic protein synthesis is formylmethionine?

A

immediate immune response: human white blood cells contain receptors that react with peptides containing formylmethionine

69
Q

Where does the first AA-tRNA bind in the large ribosomal subunit?

A

The P site

70
Q

What AA-tRNA is paired with the stop codon?

A

TRICK QUESION!!! there is no AA-tRNA for stop codons

71
Q

What is transferrin?

A

A blood protein that transports iron the cytoplasm when cells require

72
Q

What is ferritin?

A

A blood protein that binds excess iron

73
Q

What enzyme regulates the synthesis of transferrin and ferritin?

A

Aconitase

74
Q

What happens when an iron ion comes into contact with aconitase?

A

It releases from the mRNA of transferrin and ferritin

75
Q

What happens when an individual does not have enough folic acid/vitamin b12 in their diet?

A

Immature blood cells cannot complete DNA synthesis and they become enlarged

76
Q

Tetracycline

A

Binds to small ribosomal subunit in bacteria and prevents binding of new AA-tRNAs to A site

77
Q

Streptomycin

A

-antibioti

c-Binds to small ribosomal subunit and interferes with initiation of translation

78
Q

Chloramphenicol

A
  • antibiotic

- blocks peptidyl transferase, preventing peptide bond formation in bacterial protein synthesis

79
Q

Erythromycin

A
  • antibiotic

- Bind to the large subunit and block translocation of ribosomes on mRNA

80
Q

Clindamycin

A
  • antibiotic

- Bind to the large subunit and block translocation of ribosomes on mRNA

81
Q

Puromycin

A
  • both pro and eukaryotes
  • resembles tRNA, but cannot be elongated-terminates elongation
  • used in research
82
Q

Diphteria Toxin

A

Inactivates eukaryotic elongation factor and prevents translocation

83
Q

What are the 4 main enzymes used as “tools” for genetic engineering?

A

1) DNA polymerase
2) Reverse Transcriptase
3) Restriction Endonucleases
4) DNA Ligase

84
Q

What are the 3 main vectors used as “tools” in genetic engineering?

A

1) Plasmids
2) Bacteriophages (viruses)
3) Large Vectors (Hybrid of above)

85
Q

What do you do if your desired DNA sequence is unknown?

A

Create a DNA Library then screen for the fragment of interest

86
Q

What do you do if your desired RNA sequence is unknown?

A

Create a cDNA library, then screen for desired fragment

87
Q

What DNA polymerase is used in the laboratory for PCR and why?

A

Taq-Polymerase because it is heat stable

88
Q

What is the most common bacteriophage vector?

A

Lambda Phage

89
Q

What is a cosmid?

A

Hybridization of a Lambda Phage and a plasmid, allowing for larger gene insertion into bacteria

90
Q

What are the steps of PCR?

A

1) Denaturation (95C)
2) Primer annealing (40-60C)
3) DNA extension (72C)
4) Repeat

91
Q

What ingredients are required for PCR?

A
  • DNA
  • Taq-polymerase
  • Nucleotides
  • Primers
92
Q

How is Reverse Transcription different from PCR?

A

You synthesize a strand of cDNA first, just one round. Then remove RNA and perform normal PCR.

93
Q

How does solid-phase DNA synthesis differ from PCR?

A
  • Anhydrous conditions
  • Used for short DNA strands (up to 100bp)
  • No Template necessary
  • Can design any desired sequence
94
Q

What is southern, northern, and western blot used for?

A

To detect DNA, RNA, and Proteins respectively in a sample

95
Q

What is transfection?

A

the transfer of DNA into ahost

Genetics Term 1 (7 decks)

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