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Medical biology and genetics > Chpt 6 > Flashcards

Chpt 6 Flashcards

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1
Q

Each strand of DNA serve as a template for the synthesis of a new complementary strands.

A

True

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2
Q

What are the causes of DNA damage?

A
  • chemicals and radiation in the environment

- by reactive molecules that are generated inside the cell.

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3
Q

Which of the following is true?
A. genetic information in DNA can be accurately copied at high speed
B. Each DNA molecule can replicate its genes before passing them on to its descendants
C. Cluster of proteins together form a replication machine.
D. All
E. None

A

D

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4
Q

James Watson and Francis Crick proposed a ……………………. as a way of DNA
duplication

A

semiconservative replication

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5
Q

Which of the following is not true?
A. DNA Synthesis Begins at replication origins.
B. DNA synthesis happen by separating a short length of DNA a few base pairs at a time therefore does not require a large energy.
C. Replication origins contain C-G-rich stretches
D. The human genome, has an average of 220 replication origins per chromosome

A

C

Replication origins contain A-T-rich stretches (DNA rich in A-T base pairs is relatively easy to pull apart)

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6
Q

What is the function of initiator protein?

A

-bind to DNA at a replication origin and locally opens up the double helix

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7
Q

All are true except
A. DNA molecules being replicated contain Y-shaped junctions called replication forks
B. Two replication forks are formed at each replication origin
C. At each fork, a replication machine moves along the DNA, opening up the two strands of the double helix and using each strand as a template to make a new daughter strand.
D. The two forks move away from the origin in same directions, unzipping the double helix & replicating the DNA

A

D

The two forks move away from the origin in opposite directions, unzipping the double helix & replicating the DNA

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8
Q

DNA replication in bacterial and eukaryotic chromosomes is termed as ………………

A

bidirectional

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9
Q

Which of the following is not true about DNA polymerase?
A. DNA polymerase unwinds the DNA molecule from its tightly woven form
B. DNA polymerase enzyme is at the center of the replication machine
C. DNA polymerase synthesizes DNA using a parental strand as template
D. Catalyzes addition of nucleotides to the 3ʹ end

A

A

helicase unwinds the DNA molecule from its tightly woven form

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10
Q

The incoming nucleotide, enters the reaction as a ………………..

A

deoxy- ribonucleoside triphosphate

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11
Q

Where does the polymerization get its energy?

A

Hydrolysis of one of deoxyribonucleoside triphosphate high-energy phosphate bonds fuels the reaction.

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12
Q

Which of the following is true?
A. polymerization reaction is irreversible
B. deoxyribonucleoside triphosphate links the nucleotide monomer to the chain, releasing pyrophosphate.
C. DNA polymerase dissociate from the DNA each time it adds a new nucleotide
D. DNA polymerase catalyze covalent linkage of nucleotide into growing new strand
D. All except A
E. All except C

A

E
DNA polymerase does not dissociate from the DNA each time it adds a new nucleotide to the growing strand; it stays associated with the DNA and moves along the template strand

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13
Q 
New DNA chain can be synthesized
A. In both directions
B. 5ʹ-to-3ʹ direction only
C.3ʹ-to-5ʹ direction only
D. randomly in one of the directions
A

B

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14
Q

What allows DNA replication in the 3’-5’ direction?

A

Backstitcing of Okazaki fragments

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15
Q

Which of the following is false regarding 3ʹ-to-5ʹ direction DNA synthesis?
A. Are made discontinuously, in successive, separate, small pieces
B. DNA polymerase is moving backward compared to the direction of replication-fork
C. The resulting small DNA pieces called Okazaki fragments are later joined together to form new strand.
D. The DNA strand that is made discontinuously is called the leading strand the other strand is the lagging strand.

A

D

The DNA strand that is made discontinuously is called the lagging strand the other strand is the leading strand.

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16
Q

What are the two special qualities DNA polymerase that greatly increase the accuracy of DNA replication?

A
  1. Only when the match is correct does DNA polymerase catalyze the reaction
  2. proofreading-When a mistake occurs and the wrong nucleotide is added, it can correct the error
17
Q

Which of the following is true?
I. Polymerization and proofreading are carried out by similar catalytic domains in the same polymerase molecule
II. proofreading is carried out by nuclease that cleaves phosphodiester backbone.
III. If the previously added nucleotide is correctly base-paired the polymerase adds the next nucleotide
IV. If the previously added nucleotide is wrong base-paired, the polymerase clips off the mispaired nucleotide and tries again
A. I, II, IV
B. II, III, IV
C. I, III, IV
D. I, II, III

A

B

Polymerization and proofreading are carried out by different catalytic domains in the same polymerase molecule

18
Q 
What is the function of the enzyme ?
A. nuclease
B. DNA ligase
C. DNA polymerase
D. primase
E. DNA helicases
A

A. nuclease- catalyze the cleavage of phosphodiester bonds
B. DNA ligase- joins the ends of the DNA fragment together
C. DNA polymerase - called a repair polymerase replaces RNA to DNA
D. primase- an example RNA polymerase, an enzyme that synthesizes RNA using DNA as a template
E. DNA helicases- unwinds the DNA molecule from its tightly woven form

19
Q

Which of the following is true?
A. RNA primer is needed only to start replication at a replication origin for the leading strand
B. Single- strand DNA-binding proteins keeps unzipped DNA to stay unzipped and elongated to form template
C. DNA topoisomerases makes small cuts and ligates to prevent local unzipping of the DNA, which creates tension in the DNA that might interfere with replication
D. All

A

D

20
Q

……………… can be replicated to the chromosome tip

………………needs a primer to continue replication

A
  • Leading strand

- Lagging strand

21
Q

which of the following is true about telomerase?
A. helps ending of the replication of the lagging strand
B. Telomerases extend the template strand
C. Telomerase carries a short piece of RNA (blue) with a sequence that is complementary to the DNA repeat sequence
D. Telomerase adds more repeats to the telomere repeat sequences at the 3ʹ end of the template strand which allows the lagging strand to be completed by DNA polymerase without shrinking the DNA.
E. All

A

E

22
Q

What are the factors that cause damage to DNA?

A

thermal collisions
exposure to reactive metabolic by-products, DNA-damaging chemicals
radiation

23
Q

The basic pathway for repairing damage to DNA is

  1. The DNA gap is repaired
  2. Nucleases which cleave the covalent bonds that join the damaged nucleotides leaves a gap on one strand of the DNA double helix
  3. repair DNA polymerase makes a complementary copy from the undamaged strand leaving a break (nick) in the sugar–phosphate backbone of the repaired strand
  4. The damaged DNA is recognized and removed by one of a variety of mechanisms
  5. This nick in the helix is sealed by DNA ligase
A

4, 2, 1, 3, 5

24
Q

Nucleotides on one strand that are damaged can be repaired using the information present in the complementary strand.
True/ False

A

True

25
Q

what are the two basic strategies that cells use to handle damage in both strands of double helix in DNA?

A

1) nonhomologous end joining

2) homologous recombination

26
Q

Which of the following is true
A. nonhomologous end joining rapid stick the broken ends back together before the DNA fragments drift apart and get lost.
B. nucleotides are often lost at the site
of repair and might cause mutations during homologous recombination
C. Break is repaired with no loss of nucleotide at repair site in nonhomologous end joining.
D. nonhomologous end joining can be a risky strategy for fixing broken chromosomes while homologous recombination are error-free strategy repair
E. A and C
F. A and D

A

F
-nucleotides are often lost at the site
of repair and might cause mutations during nonhomologous end joining.
-Break is repaired with no loss of nucleotide at repair site in homologous recombination

27
Q

A mutation in a single nucleotide in a hemoglobin gene can cause cells to make hemoglobin with an incorrect sequence of amino acids and can cause ………………..

A

sickle-cell anemia

28
Q

Inherited disease, illustrates the importance of
……………………….
Cancer and other diseases illustrate the importance of
……………………….

A
  • ) protecting reproductive cells (germ cells) against mutation.
  • ) protecting all cells (somatic cells) against mutation.

Medical biology and genetics (4 decks)

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