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Genetics > Module 7 > Flashcards

Module 7 Flashcards

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1
Q

What is the central dogma?

A

DNA replication > transcription > translation

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2
Q

T/F Genetic information flows from DNA to RNA to Protein

A

TRUE

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3
Q

Each parental strand serves as a template for formation of what?

A

antiparallel, complementary
daughter strand

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4
Q

Completion of replication results in the formation of what?

A

two identical daughter
duplexes

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5
Q

Define semi-conservative

What direction is DNA synthesized?

A

one parental and one
daughter strand

5’ to 3’

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6
Q

DNA replication is most often ___________, proceeding in
both directions from each origin of replication, forming a what?

A

bidirectional

replication bubble

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7
Q

Bacterial chromosomes have how many origins of replication?

Eukaryotic?

A

a single origin

MULTIPLE origins

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8
Q

why is it logical to have an AT
rich region here?

A

fewer hydrogen bonds, making it
easier to separate

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9
Q

What binds at the origin and opens the DNA double helix in both directions away from the origin?

A

helicase

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10
Q

Why do Single-strand binding proteins (ssb) bind the
separated DNA strands?

A

to prevent them from reannealing

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11
Q

Unwinding of circular chromosomes creates stress and can lead to?

Which enzyme catalyze controlled cleavage and rejoining of DNA that prevents over-winding?

A

supercoiled DNA

topoisomerase

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12
Q

What builds new strands
5ʹ-3ʹ?

What replaces RNA
primers with DNA?

A

DNA pol III

DNA pol I

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13
Q

DNA _____ seals nick at 5ʹ end of
replaced primer

A

ligase

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14
Q

What other protein involved in DNA
replication ligates DNA?

A

Topoisomerase cleaves and ligates DNA to
avoid super-coiling

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15
Q

Which protein blocks extension of
replication fork?

A

Tus protein

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16
Q

EUKARYOTIC

Multiple origins along a (CIRCULAR OR LINEAR) chromosome

T/F Termination occurs at chromosome ends

  • ______ __________ epsilon responsible for leading
    strand synthesis
  • DNA polymerase delta (lagging strand*) runs
    into ___’ end of adjacent Okazaki fragment, causing
    displacement and a single-strand

____________________ cleaves the flap

A

LINEAR

TRUE

DNA polymerase

Flap endonuclease (FEN1) cleaves the flap

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17
Q

What is the chromosome shape of prokaryotes and eukaryotes?

A

🦠 Prokaryotes: Circular
🧬 Eukaryotes: Linear

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18
Q

How many origins of replication do prokaryotes and eukaryotes have?

A

🦠 Prokaryotes: One (singular)
🧬 Eukaryotes: Multiple

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19
Q

What direction does DNA replication occur in both prokaryotes and eukaryotes?

A

Bidirectional (5’ to 3’)

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20
Q

Where does DNA replication terminate in prokaryotes and eukaryotes?

A

🦠 Prokaryotes: ter sites (Tus proteins help stop replication)
🧬 Eukaryotes: Chromosome ends

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21
Q

Do prokaryotes need an end-replication solution?

A

🦠 No, because their DNA is circular

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22
Q

What is the end-replication solution for eukaryotes?

A

Telomeres

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23
Q

Which enzyme synthesizes the leading strand in prokaryotes and eukaryotes?

A

🦠 Prokaryotes: DNA pol III
🧬 Eukaryotes: DNA pol epsilon

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24
Q

Which enzyme removes primers in prokaryotes and eukaryotes?

A

🦠 Prokaryotes: DNA pol I
🧬 Eukaryotes: FEN1

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25
Which enzymes are involved in DNA replication in both prokaryotes and eukaryotes?
✔ Topoisomerase ✔ Helicase ✔ SSB (Single-Strand Binding Proteins) ✔ Primase ✔ Ligase
26
Match each enzyme with its functions A. Topoisomerase B. Helicase C. SSB (Single-Strand Binding Proteins) D. Primase E. Ligase Seals gaps in DNA Stabilizes unwound DNA Unwinds DNA Relieves supercoiling Lays down RNA primers
A. Topoisomerase – Relieves supercoiling B. Helicase – Unwinds DNA C. SSB (Single-Strand Binding Proteins) – Stabilizes unwound DNA D. Primase – Lays down RNA primers E. Ligase – Seals gaps in DNA
27
Mitochondria have their own _________ genomes
circular
28
How fast are DNA polymerases in prokaryotes and eukaryotes?
🦠 Prokaryotic (DNA pol III in E. coli): 700-1000 bases/second 🧬 Eukaryotic DNA polymerases: 50-100 bases/second
29
How often do DNA polymerases make mistakes?
~1 in 100,000 bases
30
How do DNA polymerases correct mistakes?
3' → 5' exonuclease activity (proofreading)
31
How much does proofreading improve accuracy?
Reduces error rate to ~1 in 100 million bases
32
How do other repair systems improve accuracy further?
- continuously scan for errors resulting in low error rates ~1 in 10 billion bases (10⁻¹⁰)
33
What is the final DNA mutation rate per base pair after repair?
1 in 10 billion bases (1 × 10⁻¹⁰/bp)
34
How often does a mutation occur in humans?
1 mutation per 3 cell divisions
35
How many novel mutations are in each sperm and egg cell?
Sperm cell: ~124 novel mutations Egg cell: ~10 novel mutations
36
How many cell divisions occur before sperm and egg formation?
Sperm: ~400 divisions from zygote Egg: ~30 divisions from zygote
37
What is used instead of Helicase, SSB, and topoisomerase to denatures DNA?
heat
38
20bp single stranded DNA that flanks your target region
Primers
39
which DNA polymerase is heat resistant
DNA polymerase III
40
The traditionally used DNA polymerase, Taq polymerase, is isolated from what and found where?
Thermus aquaticus, which is found naturally in hot springs
41
Which polymerase can handle very very hot temperatures – hotter than what is needed for DNA denaturation?
Taq polymerase (Thermus aquaticus) 70 -75 Celsius
42
name the 4 Steps of PCR
1. Denaturation: (rxn heated to ~95°C to denature the DNA) 2. Primer annealing: (rxn temperature is reduced to ~45–68°C so primers can hybridize) 3.Primer extension: (rxn raised to ~72°C to allow Taq polymerase to synthesize DNA) 4. Repeat steps 10-35 times (DNA product increases at ~2n, where n = # of cycles)
43
1 cycle = _ copies _ cycles = 4 copies _ cycles = _ copies 4 cycles = _ copies
1 cycle = 2 copies 2 cycles = 4 copies 3 cycles = 8 copies 4 cycles = 16 copies
44
Amplified DNA fragments are separated from the rest of the reaction mixture by what?
gel electrophoresis
45
1. DNA is _________ charged, so it travels towards the positive electrode? 2. In a gel, smaller (shorter) DNA molecules move slower or faster? 3.What is used to determine DNA size?
1. negatively 2. faster 3. A ladder
46
47
1. Variable number tandem repeats (VNTRs/STRS short tandem) are used as what? 2. TNRR units up to how many bp in length found throughout the genome?
1. a type of genetic marker 2. up to 20 bp in length
48
T or F VNTRs are inherited, and can be detected through PCR amplification
True
49
Some short tandem repeats can cause what?
genetic disease (e.g., Friedreich Ataxia, Huntington’s Disease, Fragile X syndrome
50
The 2 steps to visualize sequence of bases from DNA fragment of interest?
1. Dideoxynucleotide DNA sequencing (dideoxy sequencing), aka chain termination PCR? 2. (Capillary) electrophoresis of PCR products
51
Dideoxy sequencing starts with what?
a regular PCR
52
In addition to regular dNTPs, each reaction contains a small amount of what (dd which lacks a 3¢-OH group)?
one dideoxynucleotide
53
Whenever a ddNTP is incorporated into the product DNA molecule, replication ceases this is known as what?
“chain termination PCR
54
What percentage of the human genome codes for proteins?
2%
55
_________ Strand- Replicated continuously to the end _________ Strand - Requires primers and can't fully replicate _________________ - No room for final lagging strand primer _____________ - Repetitive sequences that protect genes
Leading Lagging End-Replication Problem Telomeres
56
What is the repeated telomere sequence in vertebrates? How many times is the telomere sequence repeated? Are telomeres conserved across vertebrates? What remains after replication at the telomere end? Which strand of telomere DNA has the overhang?
5’- TTAGGG -3’ 300-5000 repeats Yes, they are highly conserved. A 3' overhang (~50 bases) The G-rich strand
57
What does telomerase use as a template?
An RNA template complementary to the leading strand overhang
58
What is the function of telomerase?
Extends the leading strand so the lagging strand can be synthesized fully
59
Why is telomere length important?
chromosome stability, cell longevity, and reproductive success
60
Where is telomerase active in eukaryotes?
germ-line cells and some stem cells
61
Where is telomerase inactive?
differentiated somatic cells
62
What happens if telomerase is reactivated?
can lead to aging cells that continue to proliferate, a feature of many cancers
63
What is Polymerase Chain Reaction (PCR)?
DNA replication in a tube that makes millions of copies of a short DNA segment.
64
What can PCR be used for?
Cloning, gene detection, gene analysis, sequencing, and repeat analysis

Genetics (12 decks)

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