LS 7A - Week 8 - Practice Exam Questions

C.) The fragment joining function of ligase

Consider a cell in which one of the proteins involved in DNA replication is altered. This alteration results in an increased occurrence of single-stranded DNA breaks in the newly synthesized DNA. Which protein function is most likely nonfunctional in this situation? A.) The strand separation function of single-stranded binding protein (SSB) B.) The unwinding function of helicase C.) The fragment joining function of ligase D.) The winding stress relief function of topoisomerase E.) The proofreading function of DNA polymerase

E.) one leading strand and one lagging strand.

Each DNA parent strand within a replication bubble acts as a template strand that produces: A.) only lagging strands. B.) two leading strands or two lagging strands. C.) only leading strands. D.) either a leading strand or a lagging strand. E.) one leading strand and one lagging strand.

A.) Malignant melanoma cells would have active telomerases that constantly replenish and lengthen telomeres.

Imagine that a doctor is culturing two types of cells: one from a malignant melanoma and one from a normal skin sample. How would you expect these two cell populations to differ? A.) Malignant melanoma cells would have active telomerases that constantly replenish and lengthen telomeres. B.) Malignant melanoma cells would have telomeres that shorten during successive rounds of replication. C.) Malignant melanoma cells would have inactive telomerases, so their telomeres would shorten during successive rounds of replication. D.) Normal skin cells would have active telomerases that constantly replenish and lengthen telomeres. E.) Normal skin cells would have telomeres that do not shorten during successive rounds of replication.

C.) X and Y

In the diagrams below, the horizontal lines represent double-stranded DNA and the numbers are regions within the DNA. The sites labeled W, X, Y, and Z denote the locations of cleavage sites for the restriction enzymes W, X, Y, and Z, respectively. The DNA at the left is located in a bacterial plasmid vector and that on the right is located in chromosomal DNA. Each restriction enzyme produces ends that can pair with the ends of other DNA fragments produced by the same restriction enzyme but not with the ends produced by any of the other enzymes shown. A researcher plans to produce a clone with the genomic DNA inserted into the vector in the orientation 1-4-3-2. Which two enzymes should be used to cleave the vector and the chromosomal DNA to produce complementary ends that will lead to this result? A.) X and Z B.) Y and Z C.) X and Y D.) W and Z E.) W and Y F.) W and X

D.) The lagging strand glows in this way because its RNA primers are required for each Okazaki fragment and are closely spaced.

To cells that are defective in primer removal, you add fluorescent ribonucleotides when the cells are undergoing DNA replication. In this case, you observe that one strand glows more than the other not only near the replication fork but also at intervals along its length. Which strand glows in this way and why? A.) The leading strand glows in this way because it is synthesized continuously. B.) The leading strand glows in this way because it is synthesized discontinuously. C.) The lagging strand glows in this way because it is synthesized continuously. D.) The lagging strand glows in this way because its RNA primers are required for each Okazaki fragment and are closely spaced.

D.) BclI 5' T^GATCA 3'

You would like to ligate a fragment you cleaved with the restriction enzyme BamHI into a plasmid you cleaved with a different enzyme. Which of these enzymes' overhangs will be compatible with BamHI-generated fragments? BamHI sequence and cleavage site: 5' G^GATCC 3' (^ indicates cut site) A.) HpaI 5' GTT^AAC 3' B.) PstI 5' CTGAC^G 3' C.) EcoRI 5' G^AATTC 3' D.) BclI 5' T^GATCA 3'

B.) 5'-GG/ATCC-3' 3'-CCTA/GG-5'

A certain restriction enzyme X cleaves double-stranded DNA at the sequence shown, where the slash indicates where each strand is cleaved. 5'-AA/ATTT-3'3'-TTTA/AA-5' Note that the cleavage results in a two-base pair single-stranded region at the 5' end that allows the cleaved ends to undergo base pairing. Which of the restriction enzymes that cleave double-stranded DNA (indicated by the slash) would produce overhanging ends able to pair with those produced by enzyme X? A.) 5'-AAA/TTT-3' 3'-TTT/AAA-5' B.) 5'-GG/ATCC-3' 3'-CCTA/GG-5' C.) 5'-GGA/TCC-3' 3'-CCT/AGG-5' D.) 5'-GGAT/CC-3' 3'-CCTA/GG-5' E.) 5'-AATA/TT-3' 3'-TT/ATAA-5'

A.) one; many

As a piece of linear DNA is replicated, the leading strand will have _____ RNA primer(s) and the lagging strand will have _____ RNA primer(s). A.) one; many B.) one; one C.) many; many D.) many; one

D.) cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with restriction enzyme Y

Assume you are trying to insert a gene into a plasmid. Someone gives you a preparation of genomic DNA that has been cut with restriction enzyme X. The gene you wish to insert has sites on both ends for cutting by restriction enzyme Y. You have a plasmid with a single site for Y but not for X. Your strategy should be to: A.) cut the plasmid twice with restriction enzyme Y and ligate the two fragments onto the ends of the DNA fragments cut with restriction enzyme X B.) insert the fragments cut with restriction enzyme X directly into the plasmid without cutting the plasmid C.) cut the plasmid with restriction enzyme X and then insert the gene into the plasmid D.) cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with restriction enzyme Y

C.) Lane K

Below on the left is a diagram of double-stranded DNA of a circular plasmid from a bacterial cell. The positions X, Y, and Z are sites where the plasmid DNA is cleaved by restriction enzymes X, Y, and Z, respectively. The numbers are the size in kilobase pairs (kb) of the DNA regions between the restriction sites. On the right is a diagram of an electrophoresis gel. Lane 1 is the ladder, comprised of DNA fragments that range in size from 1-12 kb showing the position of each band size after electrophoresis. The other lanes are DNA bands observed from digestion of the plasmid with one of more of the restriction enzymes. Which lane contains the DNA fragments produced by digestion of the plasmid with enzyme X only? A.) Lane H B.) Lane Q C.) Lane K D.) Lane M E.) Lane L

A.) Lane H

Below on the left is a diagram of double-stranded DNA of a circular plasmid from a bacterial cell. The positions X, Y, and Z are sites where the plasmid DNA is cleaved by restriction enzymes X, Y, and Z, respectively. The numbers are the size in kilobase pairs (kb) of the DNA regions between the restriction sites. On the right is a diagram of an electrophoresis gel. Lane 1 is the ladder, comprised of DNA fragments that range in size from 1-12 kb showing the position of each band size after electrophoresis. The other lanes are DNA bands observed from digestion of the plasmid with one of more of the restriction enzymes. Which lane contains the DNA fragments produced by digestion of the plasmid with enzymes X and Y and Z? A.) Lane H B.) Lane Q C.) Lane K D.) Lane M E.) Lane L

D.) Lane M

Below on the left is a diagram of double-stranded DNA of a circular plasmid from a bacterial cell. The positions X, Y, and Z are sites where the plasmid DNA is cleaved by restriction enzymes X, Y, and Z, respectively. The numbers are the size in kilobase pairs (kb) of the DNA regions between the restriction sites. On the right is a diagram of an electrophoresis gel. Lane 1 is the ladder, comprised of DNA fragments that range in size from 1-12 kb showing the position of each band size after electrophoresis. The other lanes are DNA bands observed from digestion of the plasmid with one of more of the restriction enzymes. Which lane contains the DNA fragments produced by digestion of the plasmid with enzymes X and Y? A.) Lane H B.) Lane Q C.) Lane K D.) Lane M E.) Lane L

B.) Lane Q

Below on the left is a diagram of double-stranded DNA of a circular plasmid from a bacterial cell. The positions X, Y, and Z are sites where the plasmid DNA is cleaved by restriction enzymes X, Y, and Z, respectively. The numbers are the size in kilobase pairs (kb) of the DNA regions between the restriction sites. On the right is a diagram of an electrophoresis gel. Lane 1 is the ladder, comprised of DNA fragments that range in size from 1-12 kb showing the position of each band size after electrophoresis. The other lanes are DNA bands observed from digestion of the plasmid with one of more of the restriction enzymes. Which lane contains the DNA fragments produced by digestion of the plasmid with enzymes X and Z? A.) Lane H B.) Lane Q C.) Lane K D.) Lane M E.) Lane L

E.) Lane L

Below on the left is a diagram of double-stranded DNA of a circular plasmid from a bacterial cell. The positions X, Y, and Z are sites where the plasmid DNA is cleaved by restriction enzymes X, Y, and Z, respectively. The numbers are the size in kilobase pairs (kb) of the DNA regions between the restriction sites. On the right is a diagram of an electrophoresis gel. Lane 1 is the ladder, comprised of DNA fragments that range in size from 1-12 kb showing the position of each band size after electrophoresis. The other lanes are DNA bands observed from digestion of the plasmid with one of more of the restriction enzymes. Which lane xontains the DNA fragments produced by digestion of the plasmid with enzymes Y and Z? A.) Lane H B.) Lane Q C.) Lane K D.) Lane M E.) Lane L

A.) The lagging strand glows more because its RNA primer is nearer the replication fork.

Suppose you add fluorescent ribonucleotides to a cell undergoing DNA replication so that the RNA primers used in DNA synthesis glow when viewed with a fluorescent microscope. You notice that, near each replication fork, one strand glows more than the other. Which strand glows more, and why? A.) The lagging strand glows more because its RNA primer is nearer the replication fork. B.) The lagging strand glows more because it forms the "trombone loop." C.) The leading strand glows more because it forms the "trombone loop." D.) The leading strand glows more because it is elongated nearest the replication fork.

B.) Bottom Strand

The diagram below represents the replication bubble that has formed at a bidirectional origin of replication. The dotted line shows where replication first began. Use this diagram to answer the questions below. Where does lagging strand synthesis occur to the right of the dotted line? A.) Top strand B.) Bottom strand C.) Both strands

C.) Both strands

The diagram below represents the replication bubble that has formed at a bidirectional origin of replication. The dotted line shows where replication first began. Use this diagram to answer the questions below. Where is DNA polymerase found to the left of the dotted line? A.) Top strand B.) Bottom strand C.) Both strands

A.) Top strand

The diagram below represents the replication bubble that has formed at a bidirectional origin of replication. The dotted line shows where replication first began. Use this diagram to answer the questions below. Which strand is bound to more RNA primers to the left of the dotted line? A.) Top strand B.) Bottom strand C.) Both strands

D.) w and z

The parallel lines shown represent the paired strands of a DNA double helix. If this molecule undergoes one round of replication, which ends are shorter in the daughter molecules than in the parental molecules? A.) w and y B.) y and x C.) w and x D.) w and z

A.) one double-stranded DNA molecule

Which of the options is circled in this electron micrograph? A.) one double-stranded DNA molecule B.) two double-stranded DNA molecules C.) one single strand of a DNA molecule