Deck 10: Genes, Chromosomes and Dna

Question 1

Eukaryotic chromosomes are

A) composed of double-stranded DNA associated with protein.
B) linear structures of DNA associated with proteins called histamines.
C) composed of DNA in tight association with RNA.
D) linear structures of DNA containing a telomere which is responsible for attaching chromosomes to the mitotic spindle during mitosis.
E) circular structures of DNA.

Answer 1

composed of double-stranded DNA associated with protein.

Question 2

Humans have 46 chromosomes. The most useful criteria for distinguishing the different chromosomes under the light microscope are

A) the position of the centromere, and the length and banding pattern of the chromosomes.
B) the position of the telomere, and the size and banding pattern of the chromosomes.
C) the number of chromatids and the position of the centromere.
D) the number of telomeres and the length of the chromosomes.
E) the DNA content and the banding pattern of the chromosomes.

Answer 2

the position of the centromere, and the length and banding pattern of the chromosomes.

Question 3

In a normal diploid human cell, the nuclear genome consists of approximately

A) 6 x 10⁹ base pairs.
B) 5 x 10² base pairs.
C) 46 x 10²⁰ base pairs.
D) 3 x 10⁹ base pairs.
E) 6 x 10⁶ base pairs.

Answer 3

6 x 10⁹ base pairs.

Question 4

Two different strains of the bacteria Streptococcus pneumoniae were used in the experiments of Avery, MacLeod and McCarty: a virulent strain (S) that had a capsule and a non-virulent strain (R) that did not have a capsule. A heat-killed S strain was mixed with a live R strain and the mixture was injected into a mouse. Which statement below is CORRECT?

A) The mouse survived because the proteins from the capsule of the S strain were taken up by the R strain.
B) The mouse survived because the capsule proteins of the S strain were damaged in heating.
C) The mouse would have died if only the DNA of the S strain had been injected.
D) The mouse died because DNA of the S strain was taken up by the R strain.
E) The mouse would have survived if the S strain had not been heat treated before adding to the R strain.

Question 5

If 20 per cent of bases of a DNA double helix are adenine, what percentage of the bases are thymine?

A) 100 per cent
B) 20 per cent
C) 10 per cent
D) There is not sufficient information to determine the percentage of thymine bases.
E) 80 per cent

Question 6

If 20 per cent of the bases of a DNA double helix are adenine, what percentage of bases are cytosine?

A) 10 per cent
B) 30 per cent
C) 20 per cent
D) 60 per cent
E) 80 per cent

Question 7

The following is the sequence of bases on a strand of DNA: 5' ATGCAGC 3'. What is the sequence on the complementary strand?

A) 3' ATGCAGC 5'
B) 5' TACGTCG 3'
C) 5' ATGCAGC 3'
D) 5' CGACGUA 3'
E) 3' TACGTCG 5'

Question 8

If a section of the leading strand of DNA during replication has the sequence 5' TATCGGA 3', what would the sequence on an equivalent section of the lagging strand be?

A) 5' TATCGGA 3'
B) 3' ATAGCCT 5'
C) 5' UCCGAUA 3'
D) 5' AUAGCCU 3'
E) 3' TATCGGA 5'

Question 9

Bacteria were grown for a large number of generations in a medium containing the nitrogen isotope ¹⁵N. The bacteria were then allowed to go through two cell divisions in a medium containing the normal (and lighter) isotope ¹⁴N, after which the DNA of the bacteria was extracted and analysed. This extracted DNA (X) was compared to DNA (Y) extracted from bacteria that had always been grown in a medium containing ¹⁴N. You would expect that

A) all X would be denser than Y.
B) the density of X would be the same as Y.
C) half of X would have the same density as Y and half of X would be denser than Y.
D) X would be less dense than Y.
E) one-quarter of X would be more dense than Y, and the remainder would be the same as Y.

Question 10

A colony of actively dividing bacteria (prokaryotes) is given radioactive thymine. If a cell then replicates its chromosome and divides once, which of the following outcomes would you expect?

A) Radioactive DNA would be found in neither daughter cell.
B) All DNA and RNA bases in daughter cells would be radioactive.
C) Radioactive RNA would be found in both daughter cells.
D) Radioactive DNA would be found in both daughter cells.
E) Radioactive DNA would only be found in half of the daughter cells.

Question 11

Which of the following enzymes is NOT involved in the replication of prokaryotic DNA?

A) DNA helicase
B) DNA polymerase
C) Primase
D) Telomerase
E) DNA ligase

Question 12

The leading strand of DNA is

A) the template for the two replicate strands of DNA.
B) synthesised continuously in the 5' to 3' direction.
C) synthesised discontinuously in the 3' to 5' direction.
D) synthesised continuously in the 3' to 5' direction.
E) the initiating sequence of DNA.

Question 13

Synthesis of the lagging strand of DNA does NOT involve

A) DNA ligase.
B) synthesis of an RNA primer.
C) overall growth in the 3' to 5' direction.
D) discontinuous synthesis of short fragments in the 3' to 5' direction.
E) discontinuous synthesis of short fragments in the 5' to 3' direction.

Question 14

A new strand of DNA is synthesised using an old strand as a template. In the process

A) nucleotides are added onto the 3' end of the strand being synthesised.
B) nucleotides are added by the enzyme-catalysed formation of a bond between the 3'-phosphate of the incoming nucleotide and the 5' OH at the end of the strand.
C) a peptide bond is formed between each nucleotide.
D) the nucleotide sequence is determined by the concentration of the various nucleotides available in the cell.
E) energy for the addition for each nucleotide is supplied by ATP.

Question 15

In a nucleus the two strands of DNA are separated during replication by

A) the action of primase.
B) a rise in temperature.
C) the attachment of DNA polymerase to the replication fork.
D) breaking the covalent bonds between the bases.
E) helicase enzyme acting on the hydrogen bonds.

Question 16

In DNA synthesis, DNA helicases

A) initiate the synthesis of the RNA primer.
B) help re-establish the coiled structure of DNA after replication.
C) break the hydrogen bonds between the nitrogenous bases.
D) help with the untwisting of the supercoils.
E) stabilise the separating DNA strands with proteins.

Question 17

Deoxyribonucleoside triphosphates (dNTPs) are the building blocks used in DNA synthesis. They are added to the strand of DNA being synthesised by

A) the formation of a phosphodiester bond between the 2' dexoyribose on the growing strand and the phosphate of the incoming nucleotide.
B) the loss of two phosphates from dNTP.
C) the formation of a hydrogen bond with the 3' OH group of the newly synthesised DNA strand.
D) the formation of a phosphodiester bond between the nitrogenous base of one nucleotide and the phosphate group of another.
E) the action of the enzyme RNA polymerase.

Question 18

The 3' end of the newly synthesised DNA strand is where a

A) hydroxyl group is attached to a ribose sugar.
B) phosphate group is attached to carbon 3 of the deoxyribose sugar.
C) hydroxyl group is attached to a nitrogenous base.
D) phosphate group is attached to carbon 3 of a nitrogenous base.
E) hydroxyl group is attached to carbon 3 of the deoxyribose sugar.

Question 19

Which of the following statements is INCORRECT?

A) DNA polymerase III can synthesise from intact DNA.
B) DNA polymerase I has 5' to 3' exonuclease activity.
C) DNA polymerase I can synthesise from primed single strands.
D) DNA polymerase lll does not require an RNA primer for activity.
E) DNA polymerase III synthesises approximately fifty times faster than DNA polymerase I.

Question 20

In prokaryotes, replication begins at the

A) telomere.
B) origin.
C) terminus.
D) multiple replication sites.
E) centromere.

Question 21

Which of the following statements about the origins of replication of DNA strands in eukaryotes is true?

A) Eukaryote chromosomes have a single origin.
B) Origins are in histone-free areas of the chromosomes.
C) Replication is unidirectional from the origin.
D) Replication begins at the same time from multiple origins on the chromosome.
E) All of the statements are true.

Question 22

Telomeres

A) aid in the replication of the ends of a chromosome.
B) are the point where two chromatids are held together after replication.
C) are found in both eukaryotic and prokaryotic DNA.
D) are sequences of DNA that code for the enzyme telomerase.
E) are templates for the synthesis of the RNA primer.

Question 23

What is the role of telomeres in DNA replication in eukaryotes?

A) Telomerase adds repeat sequences to telomeres for primer attachment.
B) The initiation of replication at the 5' end of the telomere.
C) Telomeres are the site of action of restriction enzyme, to terminate replication.
D) Telomeres initiate replication forks.
E) Telomeres initiate DNA polymerase III synthesis of repeat sequences at the end of the chromosome.

Question 24

DNA replication in eukaryotes and prokaryotes is very similar. Replicating DNA in both eukaryotes and prokaryotes would be expected to have

A) one replication fork.
B) ligase-initiating replication.
C) two replicons.
D) Okazaki fragments.
E) one origin of replication.

Question 25

Eukaryotes have many more origins of replication than prokaryotes because

A) it is more important for replication to occur quickly in eukaryotes than prokaryotes and eukaryotic chromosomes are much larger than prokaryotic chromosomes.
B) eukaryotic chromosomes are much larger than prokaryotic chromosomes and replication of eukaryotic chromosomes is about twenty times slower than in prokaryotic chromosomes.
C) it is more important for replication to occur quickly in eukaryotes than prokaryotes.
D) replication of eukaryotic chromosomes is about twenty times slower than in prokaryotic chromosomes.
E) eukaryotic chromosomes are much larger than prokaryotic chromosomes.

Question 26

Which of the following statements about DNA synthesis in eukaryotes is INCORRECT?

A) Each chromosome contains many replicons.
B) Okazaki fragments are formed on the leading strand.
C) Chromosomes have many origins of replication.
D) Okazaki fragments formed are smaller than those formed in DNA synthesis in prokaryotes.
E) Replication involves the formation of two replication forks at each origin.

Question 27

Okazaki fragments are

A) larger in eukaryotes than in prokaryotes.
B) composed of RNA and DNA.
C) formed during continuous synthesis of DNA.
D) found on the leading strand of replicating DNA.
E) joined together by the enzyme primase.

Question 28

Which of the following statements best describes the Polymerase Chain Reaction (PCR)?

A) The process that repeatedly forms a polypeptide chain from a selected segment of DNA.
B) A reaction that synthesises a protein molecule from an RNA molecule.
C) A reaction that synthesises DNA from RNA.
D) A reaction in which RNA is hybridised to complementary DNA.
E) The process that repeatedly replicates a selected segment of DNA.

Question 29

In DNA synthesis, primers

A) are anti-parallel to the DNA strand that they pair with.
B) only occur on the lagging strand.
C) unwind the DNA.
D) supply starting points with 5' ends for DNA synthesis.
E) occur more often on the leading strand than on the lagging strand.

Question 30

Which of the following statements about eukaryotic chromosomes is CORRECT?

A) The DNA of eukaryotes consists of two strands each composed of a ribose sugar, a phosphate group and four nitrogen-containing bases.
B) Eukaryote chromosomes are comprised primarily of DNA condensed around histone proteins and interacting with other non-histone proteins.
C) Histone proteins assemble into groups around which the DNA coils to form a structure termed the nucleolus.
D) The ends of eukaryotic chromosomes contain a specific terminal sequence of RNA.
E) Histone proteins are small proteins with a high concentration of acidic residues which readily interact with the DNA.

Question 31

The main enzyme in DNA replication, DNA polymerase I also has a proof-reading exonuclease activity because it

A) needs to remove the DNA primer so that synthesis may be completed.
B) needs to correct pre-existing errors in the DNA before it is replicated.
C) needs to remove small DNA strands before it can begin the synthesis of the new strand.
D) needs to replace incorrect nucleotides inserted into the newly-synthesised strand.
E) detects mutations caused by sunlight and is able to remove them.

Question 32

Which of the following enzymes is not required for eukaryotic DNA synthesis?

A) RNA synthetase
B) DNA gyrase
C) DNA ligase
D) DNA polymerase
E) telomerase

Question 33

Which of the following statements about DNA replication is INCORRECT?

A) DNA polymerase I requires an RNA primer to begin replication.
B) DNA synthesis commences at a specific DNA sequence termed the origin.
C) Nucleotides are attached to the 3'OH group of the growing chain of DNA by DNA polymerase I and III.
D) DNA ligase is used to covalently link fragments of DNA.
E) The lagging strand in DNA synthesis is synthesised in short fragments.

Question 34

Which organism did Thomas Hunt Morgan study to provide strong evidence supporting the idea that chromosomes are directly involved in inheritance?

A) Mus musculus
B) Rattas rattas.
C) Arabidopsis thaliana
D) Drosophila melanogaster
E) Homo sapiens

Question 35

Which of the following statements in relation to DNA-dependent RNA polymerase is CORRECT?

A) DNA-dependent RNA polymerase attaches nucleotides to a free 5' OH group.
B) DNA-dependent RNA polymerase must build an RNA strand from an existing strand.
C) DNA-dependent RNA polymerase can initiate RNA synthesis de novo on a DNA template.
D) DNA-dependent RNA polymerase initiates synthesis via the primorase enzyme.
E) DNA-dependent RNA polymerase uses a primer to terminate strand extension.

Question 36

Which of the following statements about histones is INCORRECT?

A) Histones assemble in groups of ten to form a core upon which the DNA is bound.
B) Histones are small proteins, 11kDa in size.
C) Histones have a high concentration of basic residues.
D) Histones are abundant in the nucleus.
E) The residues in histones interact with the negatively charged sugar-phosphate backbone of DNA.

Question 37

The nucleosome is defined as

A) a chromosome bound to a nucleus.
B) the membrane surrounding the nucleus.
C) the nucleolus and nuclear envelope.
D) the nucleosome core particle only.
E) the nucleosome core particle and linking DNA.

Question 38

You are presenting a seminar to your peers on chromosomes, DNA and nuclear protein. As you are discussing the nucleosome core particle you are asked if this particle is associated with protein. How do you respond?

A) Yes, with polymerase
B) Yes, with histones
C) Yes, with condensin
D) Yes, with a nuclear pore complex
E) No

Question 39

Which of the following statement about centromeres is INCORRECT?

A) Centromeres attach chromosomes to the mitotic spindle.
B) Centromeres can be located at the ends of chromosomes.
C) Centromeres not located in the centre of chromosomes are termed metacentric centromeres.
D) Centromeres can be located in the middle of chromosomes.
E) Centromeres move chromosomes to the poles during mitosis.

Question 40

In a classic experiment by Alfred Hershey and Martha Chase, DNA from a bacteriophage was labelled with radioactive ³²P, while protein was labelled with ³⁵S. Infected bacteria were found to contain most of the ³²P but very little of the ³⁵S. How does this experiment provide strong evidence for DNA being the molecule of inheritance?

A) The result is confounding as DNA is bound to protein in the form of histones, meaning there should be equal amounts of both radioisotopes present.
B) Because DNA is present in higher concentration than protein in the host bacteria.
C) The results suggest it is DNA, not protein, being taken up by the host and passed from one generation to the next.
D) Because the proteins are more complex molecules than DNA they would be less likely to be transferred from one generation to the next.
E) All of the options listed here are incorrect.

Question 41

What is the result of semiconservative replication?

A) The generation of two semi-identical double helices.
B) The generation of a single double helix.
C) The generation of two identical daughter cells.
D) The generation of two identical double helices.
E) The generation of two identical transcripts.

Question 42

What role does DNA gyrase play in DNA replication?

A) All of the statements are true.
B) It facilitates the unwinding of the twists and supercoils of DNA.
C) It rejoins a cut phosphodiester bond.
D) It makes a transient cut in one strand of the DNA.
E) It adds negative supercoils to DNA.