BIOL 221 L14

Why must the lagging strand at a replication fork be replicated in short fragments?

• DNA is always replicated in short fragments.

• The slower replication requires DNA polymerase to start at several different places.

• It is being replicated 3’ to 5’, which is backwards and slower than 5’ to 3’.

• It is replicated toward the origin, but the fork is opening away from the origin.

• There are several DNA polymerase molecules on the lagging strand.

Which enzyme relieves the tension in DNA caused by unwinding the helix to replicate it?

• DNA polymerase

• DNA gyrase

• DNA ligase

• DNA transcriptase

• Okazaki enzyme

Which of the following is needed to replicate DNA, but is NOT needed to make RNA from DNA?

• nucleoside triphosphates

• a primer

• a template

• an enzyme

• a free 5’ OH

How does a prokaryotic RNA polymerase recognize a promoter?

• It binds to a Shine-Dalgarno sequence

• It binds to the 5’ end of the DNA

• It recognizes a “start” codon

• It binds to a sequence called an “origin of replication”

• Its sigma subunit binds to consensus sequences at -10 and -35

The following segment of double stranded DNA is transcribed using the sigma factor σ70, which recognizes as a consensus “TTGACA” at +35 and “TATAAT” at -10. Which strand is the template, and in which direction is it read?

• Top strand, read to the right.

• Bottom strand, read to the right.

• Top strand, read to the left.

• Bottom strand, read to the left.

• Either strand could be the template, read to the right.

DNA polymerase CANNOT do which of the following?

• Synthesize Okazaki fragments.

• Move on the leading strand in the same direction as helicase.

• Move 3’ to 5’ on the template strand for more than one base.

• Synthesize the lagging strand continuously.

• Hydrolyze a phosphodiester bond.

Which of the following is NOT a part of the updated (modern) “Central Dogma” of Biology?

• DNA makes RNA

• DNA makes DNA

• RNA makes DNA

• RNA makes protein

• Protein makes RNA

The following is a depiction of double stranded DNA. The transcribed region of gene abc is indicated by the box. The bottom strand is the template. Which letter(s) could represent the location of the promoter?

• X or Z

• Y or Z

• Y only

• W or Y

• X only

The consensus sequences for sigma 70 and sigma 28 are indicated below. If sigma 28 were induced in a cell, and sigma 70 repressed, which of the following statements would be true?

• The cell would have to synthesize new promoters in front of its genes.

• Sigma 28 would not be able to recognize the same RNA polymerase as sigma 70.

• A whole new group of genes would be transcribed simultaneously.

• Most of the genes transcribed by sigma 70 would also be transcribed by sigma 28.

• RNA polymerase would produce the same number of mRNA molecules from each gene with sigma 28 as it did with sigma 70.

The enzyme DNA polymerase _____.

• begins replication by binding its sigma factor to a promoter

• reads a template strand in either direction, depending on the direction of the Shine-Dalgarno sequence

• adds a new nucleotide to the 5' end of an existing nucleotide

• requires the hydrolysis of ATP to ADP in order to carry out its reaction

• requires a short sequence of bases with a 3' OH to initiate its reaction