SECTION 2
MULTIPLE CHOICE QUESTIONS: HAEM 2000 (JUNE 2011)
Fill in the computer card with pencil.
Fill in BOTH the correct and incorrect column on the MCQ card.
2, 3 or 4 answers may be correct.
1.Mitosis involves
a.
b.
c.
d.
e.
separation of chromatids in anaphase
division of cytoplasm by cytokinesis
condensation of chromatin in metaphase
nuclear membrane reforming in prophase
mitotic spindle break down in telophase
2. These organelles are involved in processing, packaging and sorting of proteins
a.
b.
c.
d.
e.
Centriole
Endoplasmic reticulum
Golgi apparatus
Mitochondrion
Nucleus
3. The following are examples of post translational modifications
a.
b.
c.
d.
e.
Carbonylation
Esterification
Glycosylation
Methylation
Phosphorylation
4. Transcription
a.
b.
c.
d.
e.
elongates RNA in 5’ to 3’ direction
is catalysed by DNA polymerase
is the synthesis of RNA from a DNA template
is regulated by transcription factors binding to the promoter
requires thymidine triphosphate
5. The following statements relate to the Polymerase Chain Reaction (PCR) technique:
a. a. a primer is needed for each end of the segment of double-stranded DNA to be
replicated
b. the final amount of DNA produced after a certain number of cycles depends on
the number of copies present at the beginning of the reaction
c. c. The reason Taq polymerase is used in a PCR reaction is because it is faster
than normal DNA polymerases
d. the annealing temperature for PCR primers is lower than the melting
temperature
e. if using RT-PCR from mRNA, the primers may be located in the introns of the
gene
6. With respect to protein analytic techniques:
a. An ELISA can be used to detect a protein antigen in a patient’s plasma
b. A Northern blot is used to transfer proteins to a membrane
c. The amino acid side chain is important in determining the properties of the amino
acid
d. In SDS-PAGE (polyacrylamide gel electrophoresis) the protein is coated with SDS
molecules
e. A protein array only detects the presence of a single protein at a time
7. With respect to DNA synthesis:
a.
b.
c.
d.
e.
DNA replication is semiconservative
Replication on the lagging strand is continuous
DNA polymerase has exonuclease functions
It only occurs in the 3’ to 5’ direction
DNA must unwind for synthesis to take place
8. With respect to RNA interference:
a. The RNA interference pathway is inherently non-specific
b. The RNA interference can be exploited as a form of gene therapy
c. Viruses cannot use the RNA interference pathway to regulate their own gene
expression
d. Mimics of microRNA precursors can be used to silence pathology-causing genes
e. Viruses exploit the RNA interference pathway to silence host genes involved in
immunity
9. With regards to reverse transcription of mRNA:
a. The result is a DNA sequence identical to the gene as it is in the original genome
b. After reverse transcription a DNA strand is produced with exactly the same
sequence as the RNA template it was produced from
c. The DNA produced from reverse transcription can be used as template in PCR
d. Reverse transcription does not require the use of primers
e. Reverse transcriptase is the enzyme responsible for synthesis of the DNA strand
10. Chromosome abnormalities
a.
b.
c.
d.
e.
Occur in approximately 1 in 20 live births
Trisomy 18 is the commonest single chromosome abnormality in live born infants
Most early miscarriages are the result of chromosome abnormalities
Trisomy 21 is the most common cause of genetic mental handicap
Involving the sex chromosomes are usually less severe
11. The following are examples of structural chromosome abnormalities
a.
b.
c.
d.
e.
47,XY,+13
Klinefelter’s syndrome
46,XY,del(22)(q16.3)
46,XX,t(2;6)(q35;p21.3)
Angelman syndrome
12. Regarding Robertsonian translocations
a. The short arms of two acrocentric chromosomes break and the short arms join
forming a new chromosome
b. Balanced Robertsonian translocation carriers have 46 chromosomes in all cells
c. The short arms of two acrocentric chromosomes break and the long arms join
forming a new chromosome
d. Individuals carrying a balanced Robertsonian translocation are at risk of
producing gametes carrying an unbalanced translocation
e. Individuals carrying a balanced Robertsonian translocation are phenotypically
normal
13. Embryos with the following karyotypes are never viable
a.
b.
c.
d.
e.
45, XO
47,XXX
45,YO
45,XX, -21
47,XX,+21
14. When testing for genetic mutations causing an autosomal recessive disease
a. Ethnic group of the patient may be helpful
b. Geographic origin of patient is important as certain diseases do not occur outside
particular specified regions
c. A rare mutation identified in a cousin is not likely to be present in the patient
d. Variable expression of the disease within the same family is due to differences at
other modifier genetic loci plus possible environmental effects
e. Not finding pathogenic mutations indicates the clinical diagnosis is incorrect
15. A woman who carries the gene for sickle cell anaemia and her homozygous normal
husband have a child with sickle cell disease. Possible explanations are
a.
b.
c.
d.
e.
Heteroplasmy
New mutation from the father
Maternal uniparentaldisomy
Genomic imprinting
Germlinemosaicism in the father
16. Cystic fibrosis (CF) is an autosomal recessive disorder with a carrier frequency of 1
in 20 in the white South African population.
a.
b.
c.
d.
e.
The birth incidence of CF is expected to be 1/1600 in this population
CF is a muscle-wasting disease
The carrier frequency of CF in the SA black population is lower (approx 1 in 40)
CF is not a concern in the Ashkenazi Jewish population
Common mutations in the CF gene have been identified in both the white and
black SA populations
17. A disease is said to be 80% penetrant
a. An individual in the general population has a 80% chance of developing the
disease
b. 80% of the individuals in a family who carry the defective gene will present with
the disease
c. 20% of individuals in a family will be affected
d. Affected individuals will present with 80% severity
e. The disease will ‘skip’ 20% of the individuals in a family who carry the defective
gene
18. A child presents with neurofibromatosis (NF), an autosomal dominant condition.
There is no family history of the disorder.
a.
b.
c.
d.
e.
one parent must carry the gene for NF
the parents are at 50% risk of having another affected child
both parents must carry a mutant NF gene
neither parent carries a mutant NF gene
the affected individual is at risk of having affected children
19. Myotonic dystrophy
a.
b.
c.
d.
e.
is a late onset genetic disorder
is dominantly inherited
is inherited only from the female parent
shows inter-generational genetic instability
is caused by expansion of a trinucleotide (CTG) repeat
20. Somatic mosaicism
a.
b.
c.
d.
e.
Occurs after fertilisation
May account for clinical variation in phenotype
Is present in the majority of patients with Down syndrome
Arises as a result of a meiotic error
45,XO[30]/46,XX[70] is an example of a mosaic karyotype
21. A 43 year old woman requests genetic counselling – she is pregnant with her first
child. She is concerned as her father died of Huntington’s disease (HD).
a. HD is an imprinting disorder
b. There is a 50% chance she has inherited HD
c. Prenatal diagnosis is indicated to test the fetus for chromosome abnormalities by
karyotyping
d. There is a 25% chance the fetus has inherited HD
e. If the fetus is male, it is more likely to be severely affected
22. Consanguinity
a.
b.
c.
d.
e.
increases the fitness of surviving offspring
increases the incidence of dominantly inherited diseases
increases the chances of homozygosity
may be the cause of a rare recessive disorder manifesting in a family
increases the risk of a new mutation occurring
23. With respect to common diseases:
a. Animal, family and polymorphism association studies can be used to determine if
there is a genetic component
b. Doctors are able to inform patients of their exact risk for getting a particular
common disease
c. The environment always plays a role in determining disease susceptibility
d. Only one test is required to decide how important genetic and environmental
factors are in a particular common disease
e. Individuals with very high genetic susceptibility are not guaranteed to acquire
the disease
24. A phenotypically normal couple have a child with spina bifida, a multifactorial
condition.
a. The recurrence risk at each subsequent pregnancy is 1 in 4
b. The recurrence risk is increased if there are other affected family members
c. DNA testing for prenatal diagnosis of spina bifida is available for subsequent
pregnancies
d. Maternal diet, lacking folic acid, may have influenced disease aetiology
e. Risk alleles found in one population cannot necessarily be applied to another
population
25. The following are examples of multifactorial diseases
a.
b.
c.
d.
e.
Lung cancer
Beta-thalassaemia
Prader-Willi syndrome
Autism
Tay-Sachs disease
26. The following are indications for prenatal diagnosis
a. A woman who is a known carrier of cystic fibrosis and whose husband has been
screened for cystic fibrosis but no pathogenic mutations were identified in him
b. A woman who is a known carrier of Huntington disease and whose husband has
been screened for Huntington disease but no pathogenic mutations were
identified in him
c. Strong family history of Alzheimer’s disease
d. Multiple spontaneous abortions
e. A husband who is normal but had a brother affected with Duchenne muscular
dystrophy
27. Genetic testing for single gene disorders may be limited if
a.
b.
c.
d.
e.
no common mutation/s exist
several different genes cause the same disorder
the mother is older than 35 years old
the gene causing the disorder is not known
the mutation lies in a non-coding region of the gene
28. Fragile-X syndrome
a.
b.
c.
d.
e.
affects predominantly females
presents with large ears, long face and prominent jaw
is a common cause of inherited mental retardation
is caused by deletion of the FMR1 gene on Xq27
can be diagnosed in the laboratory using FISH
29. Human mitochondrial DNA is useful for reconstructing human history since it
a.
b.
c.
d.
e.
has half the number of chromosomes found in the egg
is maternally transmitted
does not undergo recombination
retains a record of maternal ancestry from both parents
can be traced to a most recent common ancestor who lived in Africa
30. The non-recombining region of the Y chromosome
a.
b.
c.
d.
is passed from father to all children
can be used to infer paternity
contains biallelic markers that resolve Y chromosomes into haplogroups
contains short tandem repeats (STRs) that resolve Y chromosomes into
haplotypes
e. is unique in every male
31. Ellis-van Creveld syndrome is an autosomal recessive dwarfism trait. In the general
United States population, the incidence is 1 in 60,000. However, among the Amish in
Pennsylvania, the incidence is 1 per 200 live births. The introduction of the syndrome to
this population has been traced to the King family, who came to the area in 1744. The
following have contributed to the increased prevalence of Ellis-van Creveld syndrome in
the Amish:
a.
b.
c.
d.
e.
Heterozygote advantage
Genetic drift
Founder Effect
Random Mating
Population isolation and inbreeding
32. Regarding mitochondrial inheritance
a. Heteroplasmyis the presence of more than one mutation in the mitochondrial
genome
b. Mendelian laws of inheritance cannot be applied
c. An individual may be a mosaic with respect to a population of mutant
mitochondria
d. Females are more likely to be affected by mitochondrial diseases
e. A mitochondrial disease may be non-penetrant if too few mitochondria carry the
mutation
33. Reaction to a drug
a.
b.
c.
d.
e.
is a Mendelian (single gene) trait
does not exhibit ethnic variation
can sometimes be predicted, given an individuals’ genetic make-up
is studied in an attempt to avoid the ‘trial-and-error’ treatment approach
may be fatal if the individual is an ultra-rapid metaboliser
34. A genetic locus is classified as being polymorphic if
a.
b.
c.
d.
it exists on more than one chromosome
more than one form of the locus exists in a population
the rare allele has a frequency of more than 1%
the variant allele never gives rise to a different protein product even if present in
coding DNA
e. its commonest allele has a frequency that is less than 0.99
35. Repetitive DNA consists of
a.
b.
c.
d.
e.
arrays of tandemly repeated sequences
gene exons
unique nucleotide sequences
isolated sequences that occur at more than one site
multiple intronic sequences
36. Regarding copy number variants (CNVs)
a. 0.4% of the genomes of unrelated people typically differ with respect to copy
number
b. A copy number variant may range from 1-2 bases to 1000 megabases in size
c. Most CNVs are benign variants that will not directly cause disease
d. No relation has been established between CNVs and cancer
e. CNVs very rarely occur in the human genome
37. A paternity test shows that a mother’s genotype is 8/10 and that of her child, 8/12.
a.
b.
c.
d.
e.
Any man with a 12 allele could possibly be the child’s biological father
The biological father’s genotype could be 12/12 or 12/non-12
The mother’s 10 allele expanded to become a 12 allele in the child
This is a case of non-maternity
The numbers (8, 10, 12) refer to different possible alleles at a polymorphic locus
in the genome
38. Epigenetic regulation can involve
a.
b.
c.
d.
e.
Histone protein modifications
DNA methylation
RNA interference
Changes to the DNA sequence
DNA polymorphism in control regions
39. With respect to imprinted genes:
a. One copy of a gene is silenced, while the other copy is expressed
b. If a particular gene is methylated when it is transmitted via the sperm, the same
gene is unmethylated when it comes from an oocyte (egg)
c. All imprinted genes that come from the sperm are methylated
d. If a maternally inherited copy of a gene is methylated in the somatic cells of a
male person, then that same gene is unmethylated in the somatic cells of a
female
e. Imprinted regions are reprogrammed in the primordial germ cells, prior to
gametogenesis
40. Regarding gene therapy
a. It is possible to insert genetic material into somatic cell and germline cells
b. Plasmids are an example of a viral-based vector
c. Immune response and regular gene function disruption are two of the challenges
to successful gene therapy
d. Gene therapy for complex diseases has proven most successful as you have more
genes to potentially target than with single-gene disorders
e. Viral gene therapy vectors can be engineered to target specific cells
41. X-chromosome inactivation
a.
b.
c.
d.
e.
Occurs early in female embryonic development
Individuals with Klinefelter syndrome have two Barr bodies in each cell
An X-autosome translocated chromosome is preferentially inactivated
All genes on the inactivated X are switched off
Is an epigenetic event
42.Xist
a.
b.
c.
d.
is a gene found only on the inactive X chromosome
is not transcribed in normal males
codes for a RNA molecule that does not get translated into protein
maps to the X inactivation centre (Xic) region, from where inactivation spreads
outwards toward each telomere
e. Translocation of Xist to another chromosome has no effect on that chromosome
43. Regarding a missense mutation
a.
b.
c.
d.
e.
The codon of an amino acid is changed to a STOP codon
A base substitution at the DNA level causes an amino acid change in the protein
Sickle cell anaemia results from a homozygous missense mutation
The number of triplet repeats increases in an offspring
The antisense strand carries the mutation
44. Regarding the Human Genome
a.
b.
c.
d.
The human haploid genome is 3 000 million bases in length
There are between 20 and 25 000 coding genes in the genome
Genomic information is found in both the cell nucleus and the mitochondria
Sequence differences between human and other organisms is great, explaining
higher evolution
e. SNPs are the most abundant form of polymorphism in the genome
45. The GeneTests website can be used for the following purposes
a. Locate reputable laboratories throughout the world that offer testing for genetic
disorders
b. To provide information on the mode of inheritance of the genetic trait
c. Provide contact information regarding direct-to-consumer availability of genetic
tests
d. As a repository for storing patient test results
e. To provide initial guidelines on treatment and prognosis