Clicker Questions

According to cytological evidence, protein CMP-1 localizes to the cytoplasmic membrane. Which of the following types of biochemical data would contradict the cytological evidence?

a. CMP-1 is not very soluble in water.b. CMP-1 interacts with NP42, a protein

known to be part of the nuclear envelope.

c. CMP-1 is most abundant in cells growing in the presence of glucose.

d. CMP-1 has an atomic mass of 33,400 daltons.

Both are correct,#2 is written accordingConvention for ssDNA

What could Meselson and Stahl conclude after 1cycle of replication?

A. Conservative replication is wrongB. Dispersive replication is wrongC. Semi-conservative replication is rightD. No conclusions could be made

4

The Okazaki fragments have been ligated. Which strands are leading and which are lagging?

A) a and b are leading, c and d are laggingB) a and c are leading, b and d are laggingC) b and c are leading, a and d are laggingD) b and d are leading, a and c are laggingE) c and d are leading, a and b are lagging

3'

5'

5'

3'

a b

c d

5

(A) 2 minutes(B) 2 hours(C) 2 days(D) 2 months(E) 2 years

Humans have ~6 x 109 bp of DNAIf DNA Polymerases ∂, ℇ add 50 nt/sec, then roughly how long would it takeone replication fork to replicate the genome?

6

What will happen to the DNA when an electric current is applied to the gel?

A) It will move toward the positive electrode because it is coated with SDS

B) It will move toward the negative electrode because it is hydrophilic

C) The current will cause the DNA to denature

D) It will move toward the positive electrode because of the backbone phosphates

E) C and D

7

What determines the length of the DNA made by PCR?

A) The length of the template DNA

B) The amount of nucleotides in the reaction

C) The number of PCR cycles

D) The length of the primers

E) Where the primers anneal to the template

Which is the best mechanistic explanation for why there are no Okazaki fragments in PCR?

a. There is no ligase in a PCR reaction.b. There are no replication forks in a PCR

reaction.c. Replication during PCR amplifies much

smaller segments than the entire chromosomes that are replicated in a cell.

d. Replication starts at the 3´ ends of both strands of the target sequence in PCR.

No replication fork = no leading/lagging strand

Diploid human genome is approx. 6 x 109 bp

6 x 109 bp/4096 is roughly 1.5 million

This is the calculated answer. The actual number of protein coding genes in the human genome is 25,000. What is the restof the DNA doing!?

15

Deoxyribose

T

Which of the following base pairs can form?

1

2

3

4

A) 1, 3

B) 1, 2, 3

C) 1, 2, 3, 4

D) 2, 4

16

What would the results of Altman's original experiment have looked like if he had treated the E. coli extract with a protease before adding the pre-tRNA?

1 2 3 4

A) 1B) 2C) 3D) 4E) none of these

RNase P, the enzyme that processes pre-tRNA, is an RNA and wouldn’t be affected by protease.

Both 2 and 3 could be correct, depending whether or notthe reaction goes to completion (all starting material Is processed)

17

5' - ACCAGTACTTCGT -3'3' - TGGTCATGAAGCA -5'

A double-stranded sequence of DNA is shown below. Which is the template strand for transcription?

A) The top strandB) The bottom strandC) BothD) NeitherE) I don't know

There’s not enough information.Without a promoter you can’t tellwhich will be the template strand.

18

A DNA molecule is shown below. When RNA is transcribed from this DNA, what will the sequence of the RNA be?

A) ACCGTGA

B) ACCGUGA

C) UGGCACU

D) AGUGCCA

E) UCACGGU

ACCGTGATGGCACT

-35-10

5'

3' 5'

3'

19

Loops are often observed in eukaryotic DNA-mRNA hybrids

20

How would you explain this observation?

A) Formation of RNA-DNA hybrids causes supercoiling of the DNA and thus formation of loops.

B) Some of the DNA is still packaged in chromatin loops.

C) Loops correspond to regions of the DNA that are not represented in mRNA and so don't form hybrids.

D) Loops correspond to regions of the RNA that are not represented in DNA and so don't form hybrids.

12

34

5

6

Which bands would disappear if you disruptedthe 3’ AG splice acceptor site?

A. 1 and 2B. 3 and 4C. 5 and 6D. 2, 4, and 5E. All of them

22

Which type of mutation would cause the lac operon to be expressed all the time - even in the absence of lactose?

A) A mutation in Lac repressor that prevents it from binding to lactose

B) A mutation that prevents Lac repressor from binding to the operator

C) A mutation that disables the permease protein

D) A mutation in the active site of ß-galactosidase that destroys its enzymatic activity

This question was asked before CAPwas introduced, so you know now that thismutation would also require low glucose in the cell.

23

X-gal is an artificial substrate for ß-galactosidase. If cells producing ß-galactosidase are grown on plates that contain X-gal, the cells turn blue.

X-gal + ß-galactosidase = Blue color

What color will cells be if you grow them on plates with X-gal and lactose?

What about cells with mutant Lac repressor cannot bind lactose?

A) white, whiteB) white, blueC) blue, blueD) blue, white

Again, this question was asked before CAPwas introduced, so you know now that result would also require low glucose in the cell.

24

If cells are grown without glucose or lactose, which protein(s) would be bound to the lac operon, and would the lac operon be expressed?

A) Lac repressor bound, operon not expressedB) CAP bound, operon expressedC) Lac repressor and CAP bound, operon expressed

D) Both Lac Repressor and CAP bound, operon not expressedE) Neither Lac repressor nor CAP bound, operon not expressed

What would happen in a mutant without Trp codons in the leader peptide?

A.Only make trpE when there is TrpB.Only make trpE when there is no TrpC.Always make trpED.Never make trpEE.No idea