MG Ch. 20

Question 1

What is the function of restriction endonucleases in bacteria?

Answer 1

They provide a defense mechanism against infection by viruses.

Question 2

(T/F) Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same “sticky ends.”

Answer 2

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

Question 3

What is the purpose of the DNA sequencing primer site?

Answer 3

Allows for the ID of DNA segment cloned into plasmid

Question 4

What is the purpose of the Lac Z gene?

Answer 4

allow for ID of bacterial cells that contain cloned DNA fragment

Question 5

What is the purpose of the antibiotic resistance gene?

Answer 5

Allow for selection of bacteria that contain plasmids

Question 6

What are the steps for a cDNA library?

Answer 6

isolate mRNA from the desired cell
Create a single-stranded DNA complementary to mRNA using reverse transcriptase
Partially degrade mRNA
Synthesize cDNA with DNA polymerase
Ligate fragments into a cloning vector

Question 7

(T/F) cDNAs are complimentary copies of mRNAs

Answer 7

True

Question 8

(T/F) gel electrophoresis separates fragments based on their size.

Answer 8

True

Question 9

The role of the primers in PCR is ___

Answer 9

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

Question 10

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?

Answer 10

40

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

Question 11

(T/F) DNA fragments that are 600 bp long will migrate more quickly through a sequencing gel than fragments that are 150 bp long.

Answer 11

False