Module 2 Termination & Repair Flashcards

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1
Q

In prokaryotes, replication is complete when _____ after replicating their portion of the circular DNA

In eukaryotes, many _____ fuse to become larger until it reaches the ends of the chromosomes the ____

A

two replication forks meet

replicons
telomeres

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2
Q

Chromosomal end must be repaired. The enzyme ____ prevents shortening of lagging strands during replication. It is an RNA-directed DNA polymerase, or in other words a _____

A protein component is _____, an enzyme that can make DNA copies from RNA templates

A

Telomerase

ribonucleoprotein

reverse transcriptase

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3
Q

The ends remain unpaired as there is no place for a primer to be made. They get shorter with every division.

The end of linear chromosomes are _____, which protect the genes from getting deleted.

_____ six base pair sequence repeated 100 to 1000 times

A

telomeres

TTAGGG

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4
Q

Telomerase is active in ____ and ____ but not in ____

_____ received the Nobel Prize for _____

A

Germ cells
Adult Stem cells
Adult Somatic cells

Elizabeth Blackburn
Nobel Prize for Medicine and Physiology in 2009

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5
Q

Telomerase-deficient mice had (4)

A

tissue atrophy

stem cell depletion

organ system failure

impaired tissue injury responses

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6
Q

Fidelity of DNA replication is due to three activities:

Accurate selection of ____

Immediate _____

_____ repair

A

Accurate selection of nucleotides

Immediate proofreading

Postreplicative mismatch repair

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7
Q

There are _____ genes whose products participate in DNA repair. Fialure to repair DNA leads to a _____

A

130 genes
mutation

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8
Q

Types of DNA Damage or lesion

1) _____ The loss of an amino group. Like a C converted to a U

2) ______ of the normal bases because of failure to proofread. Like U instead of T

3) ____. Which could be single ____ or _____
The frequent cause is ____ and ____

4)____ can be formed between bases.
Chemotherapeutic drugs can crosslink DNA.
Either same strand _____ or opposite strand _____

A

Deamination

Mismatch

Breaks in backbone
Single-stranded Break
Double-stranded Break

Crosslinks covalent linkages
Intrastrand
Interstrand

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9
Q

Other lesions:

_____ Removal of purines by acid and heat; removal of altered bases by DNA glycolysis

_____ ionizing radiation, alkylating agents

_____ proofreading of incorrectly incorporated bases

____ Intercalating agents cause addition or loss of nucleotide

_____ Cyclotubyl dimers resulting from UV irradiation

_____ Breakage of phosphodiester bonds by ionizing radiation ot chemicals

_____ covalent linkage of two strands by alkylating agents

______ Disruption of structure by free radicals

A

Missing base

Altered base

Incorrect base

Bulge due to deletion or insertion

Linked Pyrimidines

Single or doube-strand breaks

Cross-linked strands

3’ - deoxyribose fragments

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10
Q

Agents that damage DNA:

Certain wavelengths of ____:
- Ionizing like _____ and ___
- longer-wavelength ____ (260 nm)

Highly-reactive ____ produced during cellular respiration

Chemicals in the environment like _____ in cigarette smole

Also chemicals used in _____

A

radiation

gamma rays & x rays

UV-C 260 nm

oxygen radicals

hydrocarbons

chemotherapy

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11
Q

Types of DNA DAMAGE:

______

A) UV light induces formation of pyrimidine dimers and joined by cyclobutane ring

B) Alkylation or addition of methyl or ethly groups

C) Carcinogens add bulky chemical groups

A

INDUCED

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12
Q

Types of DNA DAMAGE:

______

A) deamination of bases

b) depurination (loss) resulting to a cleavage

A

SPONTANEOUS

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13
Q

Mechanisms of DNA repair:

General classes:
______ chemical reation responsible for DNA damage

______ removal of damaged bases and synthesis of replacement

A

direct reversal

Excision reversal

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14
Q

Three types of excision repair:

______
cause:_____
uses:_____,____

DNA repair mechanism that corrects damaged or altered bases by excising the specific damaged base, using specific glycosylases.

The gap is then filled with the correct nucleotide sequence by the action of DNA polymerase and ligase, restoring the integrity of the DNA.

A

Base Excision Repair (BER)

Radicals, radiation, chemo

DNA glycosylase
AP endonuclease

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15
Q

Three types of excision repair:

______
cause: ______
uses: ______

addresses a wider range of DNA damage, including bulky lesions and thymine dimers.

a stretch of nucleotides containing the damaged site is excised, and the gap is filled in through the action of DNA polymerase and ligase, ensuring the removal and repair of a larger segment of damaged DNA.

A

Nucleotide Excision Repair (NER)

UV light, hydrocarbons

Excision nuclease 30 gap

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16
Q

Three types of excision repair:

______
cause: ______
uses: _____

designed to correct errors that occur during DNA replication, such as mismatched base pairs. MMR proteins identify and remove the mismatched bases, and the correct bases are then inserted.

A

Mismatch Repair

DNA replication stress
Mismatch repair system

17
Q

Last mode of repair:

______
Causes: _____

_____ two broken ends of a chromosome are glued together, not accurate

_____ matches info from a homologous chromosome that matches the damaged one. Template usage.

A

Double-stranded break repair

High-energy radiation

Non-homologous end joining

Homologous recombination