Genetics HW Development and Cancer

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1

Which of the following DNA sequences is one strand of a restriction enzyme recognition sequence?
5’ GGGTTT 3’
5’ GGATCC 3’
5’ GGGGGG 3’
5’ AAACCC 3’

5’ GGATCC 3’

Correct. The 5’ \(\rightarrow\) 3’ sequence of the complementary strand would be the same as the 5’ \(\rightarrow\) 3’ sequence of this strand; i.e., this sequence is symmetrical about the midpoint.

2

X-Gal is included in the growth medium on which cells transformed with bacterial plasmids are grown. The reason X-Gal is included is to _______.

eliminate bacteria that do not contain plasmid DNA
minimize the chances that a vector will re-circularize without incorporating a fragment of foreign DNA
identify bacteria that contain a recombinant plasmid
eliminate bacteria that do not contain recombinant plasmid

identify bacteria that contain a recombinant plasmid

Correct. Colonies produced from cells containing a recombinant plasmid are white, whereas colonies from cells containing a nonrecombinant plasmid are blue.

3

Within a six-base DNA recognition sequence, an enzyme that cuts between the 3rd and 4th bases from the 5’ end will generate blunt ends.

True
False

True

4

BamHI cuts the sequence 5′ G|GATCC 3′. Which of the following sequences would not be recognized by this enzyme?

5′ AGCGGATCC 3′
3′ TCTTAAG 5′
3′ CCTAGGATC 5′
5′ AGGATCCGTA 3′

3′ TCTTAAG 5′

This sequence does not contain the BamHI recognition site

5

A common term for a plasmid or other DNA element that serves as a cloning vehicle is vector.

True
False

True

6

Restriction endonucleases typically recognize palindromic DNA sequences and often generate "sticky ends" or single-stranded DNA overhangs at cut sites.

True
False

True

7

Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same "sticky ends."
Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same "sticky ends."

True
False

False

Restriction endonucleases cut DNA at specific sequences, but DNA ligase must be used to bond two strands covalently with the same "sticky ends."

8

If there are five molecules of DNA containing the target region at the beginning of a PCR reaction, how many copies of the target will be present after three rounds of amplification?
If there are five molecules of DNA containing the target region at the beginning of a PCR reaction, how many copies of the target will be present after three rounds of amplification?

500
15
40
125

40

Correct. The number of target sequences is doubled with each replication cycle.

9

Immediately after the primers have annealed to the target sequence, _______.

the temperature is raised so that taq polymerase can extend the primers
the temperature is lowered so that taq polymerase can extend the primers
the annealing temperature is maintained until polymerase has finished extension of the new strands

the temperature is raised so that taq polymerase can extend the primers

Correct. The temperature is raised to 70–75\(\circ\)C, the temperature over which taq polymerase is optimally active.

10

The role of the primers in PCR is _______.

solely to define the target region
to denature the template DNA and define the target region
to define the target region and provide a 3' end that can be extended by taq polymerase
the annealing temperature is maintained until polymerase has finished extension of the new strands

to define the target region and provide a 3' end that can be extended by taq polymerase

Correct. Primers bind to end of the target DNA strands, then taq polymerase synthesizes a new strand using the target DNA as a template.

11

Which of the following molecules is not required for a PCR reaction?

Ligase
Primer
DNA
DNTPs

Ligase

Ligase is not required for a PCR reaction. The enzyme used during PCR is a thermostable DNA polymerase.

12

The thermostability of Taq polymerase is required during the annealing phase of PCR.

True
False

False

The annealing phase takes place at the lowest temperature of PCR. Taq polymerase is derived from bacteria that live in hot springs, so the enzyme is thermostable, meaning that its enzymatic properties can withstand the high temperatures needed for denaturation.

13

What is the purpose of raising the temperature to 90–95°C at the beginning of each cycle of PCR?

To renature two single DNA strands
To extend the primer
To separate the double‑stranded DNA
To attach the primer

To separate the double‑stranded DNA

The temperature is raised to denature the double‑stranded DNA molecule into single strands.

14

Which of the following statements about manual Sanger sequencing is true?

One sequencing reaction is performed.
Each of the four terminating ddNTPs is labeled with a different fluorescent dye.
The DNA sequence is read from the top of the gel to the bottom.
The DNA sequence obtained is complementary to the template strand.

The DNA sequence obtained is complementary to the template strand.

The DNA fragments produced in sequencing reactions are synthesized by DNA polymerase to be complementary to the template strand.

15

What is the function of restriction endonucleases in bacteria?

They serve no function.
They allow bacteria to genetically recombine with other bacteria.
They provide a defense mechanism against infection by viruses.
They allow bacteria to engineer new DNA fragments.

They provide a defense mechanism against infection by viruses.

Restriction endonucleases recognize and degrade viral DNA, thus preventing viral infections.

16

Which of the following statements about ddNTPs is true?

They have a free 3′‑hydroxyl group on the sugar.
They have a hydrogen at the 3′ carbon of the sugar.
DNA polymerase can add a new dNTP to a 3′ ddNTP.
They have an oxygen at the 2′ carbon of the sugar.

They have a hydrogen at the 3′ carbon of the sugar.

ddNTPs terminate synthesis because there is no 3′‑hydroxyl group onto which DNA polymerase can add nucleotides.

17

DNA fragments that are 600 bp long will migrate more quickly through a sequencing gel than fragments that are 150 bp long.

True
False

False

Small DNA fragments have less hindrance in moving through the gel, so they migrate more quickly than larger fragments.