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Cytophysiology > Chapter 7 - DNA replication (DONE) > Flashcards

Chapter 7 - DNA replication (DONE) Flashcards

1
Q

when does the replication of cellular DNA occurs?

A

S phase

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2
Q

enzyme that catalyzes the formation of new DNA strands is ?

A

DNA ploymerase

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3
Q

enzymes reducing torsional force when DNA is being replicated?

A

topoisomerases

note:Topoisomerases are an important pharmacological target for drug agents designed to inhibit DNA replication

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4
Q

size of DNA double helix?

A

about ten nucleotide pairs per helical turn

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5
Q

molecular weight of DNA?

A

(>108)

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6
Q

phosphodiester bonds?

A

The phosphodiester bonds are bonds that form between the 3′-OH groups of the deoxyribose sugar on one nucleotide with the 5′ phosphate groups on the adjacent nucleotide

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7
Q

substrate for enzyme DNA polymerases?

A

The substrates for DNA polymerases are the four deoxynucleoside triphosphates (dATP, dCTP, dGTP, and dTTP) and a single-stranded template DNA.

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8
Q

DNA is copied at about ?

A

50 bp per second

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9
Q

DNA primase function?

A

synthesizes short stretches of RNA that are complementary and antiparallel to the DNA template

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10
Q

DNA ploymerases function?

A
  • They function as a complex to initiate DNA synthesis.
  • Some DNA polymerases have 3′-5′ exonuclease activity, or proofreading ability, that allows them to remove nucleotides that are not part of the double helix. - it also removes mismatched residues, thus performing an editing function
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11
Q

DNA helicases

A

DNA helicases are a class of motor proteins required to unwind short segments of the parental duplex DNA

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12
Q

DNA primases

A

initiate the synthesis of an RNA molecule essential for priming DNA synthesis on both the leading and the lagging strands

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13
Q

Single-stranded DNA binding proteins

A
  • Single-stranded DNA binding proteins prevent premature annealing of the single-stranded DNA to double-stranded DNA
  • keep the strands protected until the complementary strands are produced
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14
Q

enzyme that catalyzes the sealing of nicks (breaks) remaining in the DNA after DNA polymerase fi lls the gaps left by RNA primers?

A

DNA ligase

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15
Q

. The supertwisting of DNA can be removed by enzymes called?

A

topioisomerases

-These enzymes relieve torsional stress in DNA by inducing reversible single-stranded break

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16
Q

This form of topoisomerase catalyzes breaks in only one strand of the double-stranded DNA, allowing unwinding of the broken strand and then rejoining of the broken ends by catalyzing the formation of new phosphodiester bonds ?

A

Topoisomerase I

17
Q

This form of topoisomerase catalyzes breaks in both strands of the double-stranded DNA, allowing both broken strands to unwind, and then catalyzes the formation of new phosphodiester bonds

A

Topoisomerase II

18
Q

A type II topoisomerase that functions ahead of the replication fork. It relaxes DNA molecules in an ATP-dependent fashion?

A

DNA gyrase

19
Q

drugs used in the treatment of urinary tract and other infections?

A

Nalidixic acid and norfl oxacin

-s inhibit bacterial DNA gyrase by inhibiting the strand-cutting reaction.

20
Q

drugs that inhibit human topoisomerase II?

A

. Doxorubicin, etoposide, and teniposide

  • These drugs act by enhancing the rate at which target topoisomerase II cleaves DNA and by reducing the rate at which these breaks are resealed.
  • used in the treatment of several neoplastic diseases (cancers
21
Q

telomerase enzyme?

A
  • is an RNA- dependent DNA polymerase, which adds TTAGGG repeats to the ends of the chromosomes
  • With the help of its RNA template, it adds a series of DNA repeats to the leading strand

-

22
Q

The rate of mutations occurring from endogenous (internal cellular) causes is termed as?

A

Basal mutation rate

23
Q

mismatch repair

A

Mismatch repair deals with correcting the mismatches of normal bases that fail to maintain normal Watson-Crick base pairing

  • This failure is typically due to the mistakes made by DNA polymerase during replication

-

24
Q

recognition of a mismatch is accomplished by which protiens?

A

MSH2, MLH1, MSH6, PMS1, and PMS2 genes

25
Q

base excision repair?

A

required to correct the spontaneous depurination and spontaneous deamination (removal of amine groups) that happen to bases present in DNA

-Base excision repair involves recognition and removal of nucleotides that have lost the bases or have been modifi ed

26
Q

Nucleotide excision repair

A

This type of repair is necessary to remove ultraviolet light–induced DNA damage as well as DNA damage from environmental chemicals.

The enzymes involved in this repair pathway consist of several proteins that are required for the excision of damaged bases in DNA by a single repair system.

27
Q

genetic disorder characterized by defective repair of thymine dimers caused by UV radiations

A

Xeroderma pigmentosum

28
Q

Double-stranded DNA repair caused by

A

ionizing radiation, oxidative free radicals, or chemotherapeutic agents

29
Q

two types of repair mechanisms exist to correct the damage the double strand DNA breakage?

A

homologous recombination and nonhomologous end joining

30
Q

homologous recombination?

A
  • This type of repair takes advantage of sequence information available from the unaffected homologous chromosome for proper repair of breaks.
  • BRCA 1 and 2 proteins normally play a role in the homologous recombination process
31
Q

Fanconi’s anemia

A

condition caused by failures in DNA recombination repair enzymes to correct the defects by homologous recombination

-

32
Q

Mutations in BRCA 1 and 2 causes?

A

breast cancer

33
Q

Nonhomologous end joining

A
  • This process permits the joining of ends even if there is no sequence similarity between them.
  • Nonhomologous end joining is especially important before the cell has replicated its DNA because there is no template available for repair by homologous recombination

Cytophysiology (13 decks)

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