Genes Flashcards
(95 cards)
1
Q
What are Chargaff’s Rules?
A
- # of A = # T (same for C&G)
2. # of A + T and C+G are equal on both strands
2
Q
What is azidothymidine? (Zidovudine)
A
- Anti-Viral Drug
- Incorperation of nucleotiees that lack 3’-OH
- Used to treat HIV
3
Q
Why doesn’t azidothymidine hurt humans?
A
- Human polymerase prefers Thymidien
- Viral Polymeraase prefers azidothymidine (AZT)
4
Q
What is methylated in DNA?
A
- A & C nucleotides
- Histones
5
Q
What keeps the two strands of DNA separate during replication?
A
-Single-stranded DNA binding proteins
6
Q
What replaces the RNA primer in DNA replication?
A
-DNA polymerase I
7
Q
What is Gyrase?
A
-The bacterial equivalent to topoisomerase
8
Q
What drug targets Gyrase?
A
-Floroquinolones
Ciprofloxacin
9
Q
How do Floroquinolones work?
A
Inhibit bacterial gyrase, causeing cell death
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
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
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
13
Q
What is a genetic disorder in which the DNA repair enzymes are damaged?
A
Xeroderma pigmentosum
14
Q
How does Ionizing radiation damage DNA?
A
It affects sugar-phosphate backbone, leading to strand breaks-It damages purine rings
15
Q
How does UV light damage DNA?
A
Causes dimerization between adjacent C and T bases
16
Q
How do repair enzymes know which strand of DNA is the parent strand?
A
The parent strand is usually more methylated
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
18
Q
What enzyme is used to treat Cystic Fibrosis?
A
Dornase
19
Q
What is homologous recombination?
A
The crhomosomal copy serves as a template so that its homologue can be repaired
20
Q
Which type of cells contain telomerase?
A
Stem cells
21
Q
What happens if a mature cell acquires telomerase?
A
Cancer
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
23
Q
What is the Hayflick Limit?
A
The point at which a cell can no longer divide, happens after ~50 divisions.
24
Q
Why is RNA less stable than DNA?
A
- Single Stranded
- 2’ OH makes RNA more prone to hydrolysis
25
What does it mean for a gene to be polycistronic?
It codes for multiple proteins
26
Which strand is the "Sense" strand?
The 5'-3' DNA strand
27
Which strand is the "Antisense" strand?
The 3'-5' DNA strand
28
In what direction is RNA synthesized?
5'-3'
29
Which DNA strand serves as a template for RNA polymerase?
The Antisense strand
30
What makes up the core promoter of Prokaryotes?
TATA box and -35 sequence
31
What does the prokaryotic transcription promoter strength depend on?
The exact sequence and distance between the promotors
32
When are prokaryotic Upstream elements necessary?
For highly expressed genes
33
What do Prokaryotic upstream elements do?
serve as additional binding sites for RNA polymerase
34
What does the operator sequence of the operon do?
Serves as a binding site for a repressor or activator
35
What is the promotor sequence of eukaryotes for?
Binding spot for Transcription factors. RNA polymerase cannot bind directly to the strand.
36
What does RNA polymerase bind to in eukaryotic cells?
The transcription factors
37
What are 2 examples of transcription factors in eukaryotes?
- Steroids
| - NF-kB
38
Why shouldn't steroids that are being administered to a patient be stopped abruptly?
dose should be gradually lowered to facilitate return to normal gene expression
39
What is NF-kB?
- Eukaryotic transcription factor
| - Regulates many immune-related proteins
40
Where are eukaryotic enhancer regions located? What is their purpose?
- 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
How are Eukaryotic genes inactivated?
- DNA and histones are methylated by DNA methyltransferase
| - histones are De-acetylated by histone deacetylase (HDAC)
42
How are Eukaryotic genes activated?
- DNA and histones are De-methylated
| - histones are acetylated
43
What do the 3 eukaryotic RNA polymerases do?
Produce:
I: rRNA
II: mRNA
III: tRNA
44
What ions are required for the function of RNA Polymerse?
Mg2+ and Mn2+
45
Does RNA polymerase require a primer?
No
46
How does RNA polymerase initiate transcription?
It loosely slides along DNA until it reaches a promoter sequence and/or transcription factors through its sigma unit
47
What sequence of DNA signals the stop of transcription?
a GC-rich region followed by an AT-rich region
48
What do release factors do?
Bind to new RNA and pull it away from RNA polymerase and the DNA template
49
What are two antibiotic examples, and one poison example of RNA polymerase inhibitors?
Antibiotic: Rifampin & ActinomycinPoison: Amanitin
50
Rifampin
- Inhibits initiation of RNA transcription in bacteria
| - Used in Tuberculosis therapy
51
Actinomycin
- antibiotic
- Inhibits elongation
- Used in cancer therapy
52
Amanitin
poison from mushrooms-Inhibits human RNA polymerase II elongation
53
What is the 5' end of eukaryotic RNA capped?
With methylguanosine triphosphate
54
What is the purpose of the 5' RNA cap?
- necessary for ribosome binding
| - Protects 5' end
55
What is the purpose of the 3' RNA Poly(A)-tail?
- Protect 3' end-Stabilize RNA
| - Regulates the half-life of mRNA
56
What is alternate splicing?
different combinations of exons from the same gene. One gene, different mature proteins
57
What is trans-splicing?
splicing of exons from two different pre-mRNA's. Only occurs in lower eukaryotes.
58
What does it mean for the genetic code to be degenerative?
There can be more than 1 codon code for 1 amino acid
59
What is the genetic cause of Huntington's Disease?
Several CAG triplets inserted into the gene for huntingtin. No shift of reading frame.
60
Before the ribosome attaches to mRNA, the mRNA must be ______
Activated by ATP, forming an aminoacyl-AMP
61
What does the wobble hypothesis say?
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
In what direction are proteins made?
Amino-to-carboxyl direction
63
Why is it that protein synthesis has no proof-reading steps?
Speed is more important than perfection-Incorrect proteins will rapidly be degraded
64
Outline the steps of mRNA export from the nucleus
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
What is required for prokaryotic mRNA translation to initiate?
Shine-Dalgarno sequence upstream of the start codon-start codon (AUG)
66
What is required for eukaryotic mRNA translation to begin?
- 5' caps
| - Start codon after 5'cap
67
What is the Shine-Dalgarno sequence?
a purine-rich sequence upstream of the start codon required for prokaryotic protein synthesis
68
Why is it important that the start codon in prokaryotic protein synthesis is formylmethionine?
immediate immune response: human white blood cells contain receptors that react with peptides containing formylmethionine
69
Where does the first AA-tRNA bind in the large ribosomal subunit?
The P site
70
What AA-tRNA is paired with the stop codon?
TRICK QUESION!!! there is no AA-tRNA for stop codons
71
What is transferrin?
A blood protein that transports iron the cytoplasm when cells require
72
What is ferritin?
A blood protein that binds excess iron
73
What enzyme regulates the synthesis of transferrin and ferritin?
Aconitase
74
What happens when an iron ion comes into contact with aconitase?
It releases from the mRNA of transferrin and ferritin
75
What happens when an individual does not have enough folic acid/vitamin b12 in their diet?
Immature blood cells cannot complete DNA synthesis and they become enlarged
76
Tetracycline
Binds to small ribosomal subunit in bacteria and prevents binding of new AA-tRNAs to A site
77
Streptomycin
-antibioti
| c-Binds to small ribosomal subunit and interferes with initiation of translation
78
Chloramphenicol
- antibiotic
| - blocks peptidyl transferase, preventing peptide bond formation in bacterial protein synthesis
79
Erythromycin
- antibiotic
| - Bind to the large subunit and block translocation of ribosomes on mRNA
80
Clindamycin
- antibiotic
| - Bind to the large subunit and block translocation of ribosomes on mRNA
81
Puromycin
- both pro and eukaryotes
- resembles tRNA, but cannot be elongated-terminates elongation
- used in research
82
Diphteria Toxin
Inactivates eukaryotic elongation factor and prevents translocation
83
What are the 4 main enzymes used as "tools" for genetic engineering?
1) DNA polymerase
2) Reverse Transcriptase
3) Restriction Endonucleases
4) DNA Ligase
84
What are the 3 main vectors used as "tools" in genetic engineering?
1) Plasmids
2) Bacteriophages (viruses)
3) Large Vectors (Hybrid of above)
85
What do you do if your desired DNA sequence is unknown?
Create a DNA Library then screen for the fragment of interest
86
What do you do if your desired RNA sequence is unknown?
Create a cDNA library, then screen for desired fragment
87
What DNA polymerase is used in the laboratory for PCR and why?
Taq-Polymerase because it is heat stable
88
What is the most common bacteriophage vector?
Lambda Phage
89
What is a cosmid?
Hybridization of a Lambda Phage and a plasmid, allowing for larger gene insertion into bacteria
90
What are the steps of PCR?
1) Denaturation (95C)
2) Primer annealing (40-60C)
3) DNA extension (72C)
4) Repeat
91
What ingredients are required for PCR?
- DNA
- Taq-polymerase
- Nucleotides
- Primers
92
How is Reverse Transcription different from PCR?
You synthesize a strand of cDNA first, just one round. Then remove RNA and perform normal PCR.
93
How does solid-phase DNA synthesis differ from PCR?
- Anhydrous conditions
- Used for short DNA strands (up to 100bp)
- No Template necessary
- Can design any desired sequence
94
What is southern, northern, and western blot used for?
To detect DNA, RNA, and Proteins respectively in a sample
95
What is transfection?
the transfer of DNA into ahost
