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Cell Bio > Exam 3 (Topic 12) > Flashcards

Exam 3 (Topic 12) Flashcards

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Biology 101 flashcards
1
Q

Each daughter DNA molecule contains one parental strand and one daughter strand

A

Semiconservative Replication

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2
Q

DNA backbone gets broken, and strands are copied and rejoined

A

Dispersive Replication

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3
Q

After replication, parent helix forms back together and daughter strands join together

A

Conservative Replication

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4
Q

How did Melson and Stahl disprove two of the hypothesis?

A

The used a density gradient centrifugation of DNA from cultured bacteria with 14N (light) and 15N (heavy). The conservative test was disproved because a mixture of light and heavy was observed. Dispersive was disproved because when heat was applied there was a separate heavy band and a separate light band, confirming the semiconservative hypothesis.

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5
Q

Why is DNA synthesized 5’–>3’?

A

Because it is endergonic which releases enough energy when broken from the 5’ triphosphate for the polymerization reaction to occur.

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6
Q

What is the function of the origin of replication?

A

To be a position where the DNA is first opened for DNA replication

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7
Q

What is characteristic about the origin of replication’s DNA sequence?

A

DNA sequences attract initiator proteins and DNA that are easy to open

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8
Q

How many replication forks does a eucaryotic chromosomes that is undergoing replication contain?

A

2 replication forks are formed at each replication origin

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9
Q

What is the purpose of the Okazaki fragments and why are they made?

A

To eventually form a continuous new DNA strand and to connect to the leading strand to make the strand continuous

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10
Q

Would you fine on DNA polymerase in a replication fork?

A

No, you would find them at the 5’ end of all Okazaki fragments. Since there can be many Okazaki fragments, there must be DNA polymerase for each fragment.

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11
Q

What is the function of the Helicase?

A

Uses ATP energy to unwind the double helix at the replication fork

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12
Q

What is the function of the single-strand binding protein?

A

Binds to the newly formed single-stranded DNA and prevents it from base pairing

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13
Q

What is the function of the sliding clamp protein?

A

Protein that binds to DNA polymerase and keeps it attached to the single-stranded DNA

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14
Q

What is the function of the clamp loader?

A

Uses ATP to assemble and attach the sliding clamp

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15
Q

Which of the four proteins from replication require ATP to perform its function?

A

Helicase and Clamp Loader

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16
Q

What is the function of primase?

A

An RNA polymerase that makes a short 10 nucleotide primer of RNA bound to the DNA template; makes a short primer that DNA polymerase can add nucleotides to

17
Q

Is primase a DNA or RNA polymerase

A

RNA

18
Q

Why must DNA replication begin with an RNA primer?

A

Because DNA polymerase cannot initiate replication without an existing nucleotide to build from

19
Q

What three other enzymes are required to remove the primer and complete DNA replication?

A

Nuclease, Repair Polymerase, DNA Ligase

20
Q

What is the function of Nuclease?

A

erases the RNA primer

21
Q

What is the function of Repair Polymerase?

A

fills the RNA gap made by nuclease

22
Q

What is the function of DNA Ligase?

A

joins the two DNA fragments

23
Q

Why can’t DNA polymerase replicate the ends of the chromosomes?

A

Because it does not have an existing strand with a 3’ hydroxyl group to replicate on

24
Q

What are telomeres?

A

special repetitive noncoding sequence that are added to end chromosomes

25
Q

What is the function of telomerase? How does it do it?

A

A DNA polymerase with a built in RNA template to synthesize new DNA. It replenishes the nucleotides that are lost by adding multiple copies of the same DNA sequence.

26
Q

Why is telomerase called a ribonucleoprotein?

A

because it contains RNA and protein reverse transcriptase subunit

27
Q

When cells do not have telomerase expressed anymore, what happens when the ends of their chromosomes lose a certain amount of DNA?

A

You lose the ends of your chromosomes and senescence (stop dividing) and apoptosis (programmed cell death) occur

28
Q

Programmed cell death

A

apoptosis

29
Q

Stop dividing

A

Senescence

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