Deck 13: Genomes, Mutation and Cancer

Question 1

Which of the following statements is true?

A) Somatic cells of organisms can be diploid, tetraploid or even hexaploid.
B) Eukaryotic genomes sometimes include plasmids.
C) Eukaryotic genomes are completely composed of linear DNA.
D) All of the above are correct.
E) Eukaryotic genomes include all of the DNA within the cell.

Answer 1

Somatic cells of organisms can be diploid, tetraploid or even hexaploid.

Question 2

Humans have

A) forty-four autosomes and two sex chromosomes.
B) twenty-two autosomes and two sex chromosomes.
C) twenty-four autosomes and two sex chromosomes.
D) twenty-two autosomes, including two sex chromosomes.
E) twenty-four autosomes, including two sex chromosomes.

Answer 2

twenty-two autosomes and two sex chromosomes.

Question 3

In eukaryotes, the nuclear genome is

A) a single, circular chromosome in the nucleus.
B) all nucleic acids in the cell.
C) the DNA in the eukaryotic cell.
D) the chromosomal DNA in the nucleus.
E) the chromosomes in gametic tissue.

Answer 3

the chromosomal DNA in the nucleus.

Question 4

Genome density

A) relates to the number of genes found per map unit of distance on a chromosome.
B) is the number of genes in relation to the genome size in base pairs.
C) is the number of genes expressed in a cell.
D) reflects an organism's complexity.
E) cannot be calculated in prokaryotes, because of their circular DNA.

Question 5

Genes are being discovered using cDNA. cDNA is

A) a direct copy of the DNA at a particular gene locus.
B) only useful if the gene product is an enzyme.
C) created from mRNA transcripts, and therefore does not include introns.
D) the complementary double-stranded DNA of a specific gene.
E) None of the answers are correct.

Question 6

A genetic map

A) describes the relative positions of genes in recombination distances.
B) defines the distance between loci in kilo bases.
C) indicates the complexity of an organism.
D) outlines the characteristics of all loci on all chromosomes.
E) measures the distance between centromeres.

Question 7

Which of the following statements about DNA is CORRECT?

A) Only 2 per cent of mammalian DNA codes for polypeptides.
B) Transposable elements repair DNA damage.
C) Introns are segments of genes that are inserted at replication forks.
D) DNA synthesis is self-perpetuating and does not require enzyme mediation.
E) Mitochondrial DNA is replicated in the nucleus.

Question 8

The coding sequence of a gene is called

A) a partitioning sequence.
B) a promoter.
C) an intron.
D) an operon.
E) an exon.

Question 9

Non-coding DNA can best be described as

A) 'junk' DNA that is of little or no value to the organism.
B) including stretches of DNA that may have an as yet undefined function for the organism.
C) DNA that is the promoter region for genes.
D) DNA that is composed of repetitive sequences of bases.
E) DNA that codes for factors that regulate gene expression.

Question 10

Which of the following statements about chloroplast chromosomes is CORRECT?

A) Chloroplasts contain multiple copies of circular DNA.
B) Chloroplasts contain a single, circular DNA molecule.
C) Chloroplasts contain a single, circular RNA molecule.
D) Chloroplast chromosomes are replicated in the nucleus of the cell.
E) Chloroplasts do not contain chromosomes.

Question 11

Ribosomal DNA is

A) synthesised by ribosomes in the nucleolus of a cell.
B) found only in the nucleolus of ribosomes.
C) repeated DNA sequences that encode the RNA components of ribosomes.
D) the DNA that codes for the ribosomal proteins.
E) variable DNA sequences that are required for the many different ribosomes found in organisms.

Question 12

A 'jumping gene' is able to insert a copy of a DNA sequence into another location. A 'jumping gene' is more often called a

A) transposable element.
B) non-coding DNA.
C) repetition sequence.
D) transcription sequence.
E) partitioning sequence.

Question 13

To manufacture DNA, the cell needs a balance in the levels of purine and pyrimidine nucleotides. This balance is controlled by

A) the enzyme ribonucleotide reductase.
B) feedback mechanisms.
C) the level of ATP in the cell.
D) restriction enzymes.
E) pinocytosis of precursors.

Question 14

The percentage of essential genes in a genome, as measured in the laboratory, is probably an underestimate because

A) many genes are only essential in poor conditions, not simulated in the laboratory.
B) the functions of many genes are, as yet, poorly understood.
C) some genes are expressed at such low levels that they are not easily detected.
D) All of the answers are correct
E) None of the answers are correct

Question 15

cDNA is used in microarrays because it

A) is complementary to the mRNA from which it was copied.
B) will bind to complementary DNA.
C) can be labelled with a fluorescent dye so that genes that it binds to can be identified.
D) single-stranded DNA is more stable than single-stranded RNA.
E) All of the answers are correct.

Question 16

Given that different organisms can have sections of DNA that are almost identical, which of the following statements is CORRECT?

A) This DNA is usually non-functional.
B) This constitutes evidence of evolution of these organisms from a common ancestor.
C) This is only true for repetitive DNA.
D) These organisms are always very closely related, as with chimpanzees and humans.
E) Identical sections of DNA will always perform the same function, regardless of the organisms in which they are found.

Question 17

Variation between individuals of a species

A) is solely a result of genetic differences.
B) has its primary source in environmental effects.
C) is a result of the deletion of specific genes.
D) is the basis upon which natural selection acts.
E) is greater than variation between members of different species.

Question 18

Spontaneous mutations

A) are rare, because of the semiconservative nature of DNA synthesis.
B) occur most frequently as a result of deamination (loss of cytosine or thymine).
C) cannot be repaired.
D) are due to translocation of one region of the chromosome to another region in the DNA.
E) occur at a rate of approximately one in one billion.

Question 19

Which of the following statements is CORRECT?

A) All chemical mutagens bind to DNA and interfere with replication.
B) New mutations are usually recessive.
C) Chemicals described as base analogues are mutagenic because they remove bases from the DNA backbone.
D) Deamination of cytosine to form uracil in the genome results in the production of a non-functional enzyme.
E) All of the answers are correct.

Question 20

Mutations may have an effect on phenotype because

A) they alter the stability of the DNA.
B) they change the amino acids encoded by the mRNA codon.
C) they remove information from the DNA code.
D) they alter the binding of transcription factors and change gene expression.
E) All of the answers are correct.

Question 21

Excision repair only works because

A) it removes entire sections of damaged double-stranded DNA and replaces them.
B) the excised single strand is accurately reformed from its complementary strand.
C) the excision repair enzymes recognise DNA damage and remove the double-stranded DNA in the area.
D) most DNA sequences are non-coding.
E) it occurs after DNA replication.

Question 22

Which of the following is NOT a form of environmental damage to DNA?

A) Deamination of cytosine
B) Hydrolytic loss of guanine
C) Radiation induced dimers
D) Photoreactivation
E) All are forms of environmental damage

Question 23

The mechanisms of DNA repair

A) are mostly enzyme-based.
B) minimise risk by killing the affected cell.
C) involve RNA-polymerase through complementary base pairing.
D) are located in the ribosomes.
E) act only during the meiotic phase of cell division.

Question 24

Ultraviolet radiation can cause two adjacent thymines in DNA to covalently bond, forming a dimer. If not repaired, this has the effect of

A) introducing substitution errors.
B) introducing replication errors.
C) breaking the DNA strand.
D) blocking DNA synthesis.
E) All of the answers are correct.

Question 25

Cancer is a general term used to describe

A) a disease where healthy tissue is irreparably damaged.
B) diseases that originate from mutations, caused by the environment, in healthy cells.
C) diseases caused by unregulated growth of cells, causing damage to tissue.
D) diseases that are genetic in origin.
E) a disease caused by translocation of regions of the chromosome causing incorrect gene expression.

Question 26

A tumorous cell is not a cancer because

A) it has not lost the ability to undergo apoptosis.
B) tumorous cells are localised, whereas cancer cells can metastasise.
C) it may still be able to repair any DNA mutations.
D) it is not necessarily caused by a genetic change.
E) tumorous cells are undifferentiated.

Question 27

Which of the following statements is CORRECT?

A) Cancer is caused by genetic alterations to cells.
B) The majority of cancers are sporadic (i.e. there is no family history).
C) Tumours are clonal in origin.
D) Cancer is not an inherited disease, but the predisposition to cancer is genetic.
E) All of the answers are correct.

Question 28

The dominant oncogene, ras

A) stimulates rates of mitosis when activated in a normal cell.
B) can be expressed constitutively when mutated.
C) is the gene for a protein which is part of a signal transduction pathway.
D) All of the answers are correct.
E) None of the answers are correct.

Question 29

Familial retinoblastoma

A) susceptibility is inherited as a recessive trait.
B) differs from non-familial retinoblastoma in that there is no recurrence in the familial form.
C) always leads to the development of tumours, usually later in life.
D) is caused primarily by acquired mutations in both alleles.
E) is caused by inheritance of a non-functional allele, plus mutation of the second allele.

Question 30

Which of the following statements is CORRECT?

A) Cancer formation requires multiple genetic changes.
B) Cancer cell genomes have a higher plasticity than normal cell genomes.
C) Many tumour repressor genes are involved in DNA repair.
D) Dominant oncogenes commonly play a role in stimulating cell growth.
E) All of the answers are correct.

Question 31

DNA repair is most efficient in preventing perpetuation of mutations if it occurs

A) during S phase.
B) during G₂ phase.
C) prior to S phase.
D) after mitosis has occurred.
E) during G_o.

Question 32

The genome of a virus is composed of

A) double-stranded DNA.
B) single-stranded DNA.
C) double-stranded RNA.
D) single-stranded RNA.
E) Any of these types of DNA or RNA.

Question 33

Organelle genomes

A) are composed of linear DNA.
B) are composed of circular DNA.
C) may be linear or circular DNA.
D) contain all the genes necessary for the functioning of the genome.
E) are all very small.

Question 34

Which of the following statements is INCORRECT?

A) Viral replication uses the host's metabolic systems.
B) Single-stranded RNA is transcribed into double-stranded RNA by a complex of viral and host proteins for replication.
C) Some cancers are caused by viruses.
D) Viruses are not considered to be living organisms as they are unable to reproduce independently of the host cell.
E) All viruses are simple structures with a coat composed of 1 or 2 proteins surrounding a simple genome.

Question 35

Transposons are

A) DNA sequences that are able to replicate and insert into another location in the genome.
B) maintained in the genome as they are replicated during genomic DNA replication.
C) genes which frequently encode enzymes which are able to recognise specific sequences to DNA and cut them.
D) able to produce RNA copies of themselves.
E) All of the statements are correct.

Question 36

A tumour suppression gene is

A) a gene whose normal function is gained during the development of cancer.
B) a dominant gene that plays a role in cell proliferation.
C) the gene Rb that suppresses cell progression to M phase during cell division.
D) a gene frequently associated with DNA transcription enzymes.
E) a gene when mutated is associated with an inherited susceptibility to cancer.

Question 37

A genome is best described as

A) the DNA sequence of an organism that represents its full genetic information.
B) an ambiguous set of genes.
C) all of the genes of a population of organisms.
D) the product of a phenome.
E) a discreet, singular genetic unit.

Question 38

Barley has a genome of 5.3 Gb. This is the same as

A) 53 000 000 000 000 bp.
B) 53 billion base pairs.
C) 530 billion base pairs.
D) 530 000 000 bp.
E) 5300 Mb.

Question 39

A coding sequence is translated into a functional peptide via a

A) protein.
B) mRNA intermediate.
C) polycistronic message.
D) tRNA intermediate.
E) coding sequences code for a transcript only, not a peptide.

Question 40

In an in-vitro experiment with DNA, an unknown enzyme and reagents are added to a tube. An RNA transcript is detected that was not present previously. What would this enzyme be?

A) Reverse transcriptase
B) DNA polymerase
C) RNA polymerase
D) DNA exonuclease
E) RNA endonuclease

Question 41

To which of the following do retrotransposons function most similarly?

A) Retroviruses
B) Retrocodons
C) Cis-transposons
D) Poly-jumping genes
E) All of the options listed here are incorrect.

Question 42

In response to certain stimuli, every gene in an individual's genome can be examined by

A) gel electrophoresis.
B) large scale sequence analysis technology.
C) southern and/or northern analysis.
D) chromatin immune-precipitation assay.
E) enzyme linked immunosorbent assay.

Question 43

You are studying a bacterial population which has originated from a single cell before being divided into two separate populations. One population is placed in a dark container and continues to develop normally, while the other is exposed to sunlight and shows an increased rate of error in its DNA replication. Which of the following is the most likely causal agent of this increasing rate of error?

A) Chemical mutagen
B) Spontaneous mutation
C) Mycotoxin
D) Mutagenic alkaloid
E) Ionising radiation

Question 44

Which of the following is INCORRECT in relation to cancer?

A) Cancer results from a series of mutations leading to changes in a cell's behaviour.
B) Cancerous cells can invade and damage other tissues.
C) Primary cancers are not the same type of cancer as secondary cancers.
D) Cancer causes unregulated cell proliferation.
E) Cancer is a genetic disease.

Question 45

When a cell has unrepaired DNA damage and progresses into mitosis, this can result in an increased rate of

A) proliferation.
B) chromosome replication.
C) gene duplication.
D) All of the answers are incorrect.
E) chromosomal recombination.