Medical Genetics and Genetic Testing
Covers advanced topics in medical genetics including inheritance patterns, molecular biology techniques, genetic testing methods, inborn errors of metabolism, and clinical applications of genetics.
Questions
Directions: The following question has four choices out of which ONLY ONE is correct.
Which of the following is used as the mainstay of treatment of hemochromatosis?
- Phlebotomy
- Blood transfusion
- Chelation therapy
- Iron therapy
Directions: The following question has four choices, out of which ONLY ONE is correct.
Testing an individual for HLA haplotype to determine risk of an autoimmune disease would be an example of
- diagnostic tests
- screening tests
- predispositional test
- predictive testing
How many alleles can result from an individual restriction fragment length polymorphism?
- 2
- 3
- 4
- Any number
Which of the following types of DNA replication or repair systems is dysfunctional in individuals with xeroderma pigmentosum?
- Base excision repair
- Mismatch repair
- Nucleotide excision repair
- Direct DNA damage
If one starts a polymerase chain reaction with a single copy of a DNA sequence approximately, how many copies will be present after 10 cycles of amplification?
- 10
- 1000
- 10,000
- 1,00,000
A dominantly inherited trait affects a child and his grandmother, but neither parent. This best illustrates which of the following principles?
- Variable expressivity
- Somatic mosaicism
- Non-penetrance
- New mutation
A mutation results in production of a protein that inhibits the action of other proteins resulting in an abnormal phenotype. The most likely mode of inheritance would be
- autosomal dominant
- autosomal recessive
- X-linked recessive
- mitochondrial
A 15 year old boy develops a disorder, which is present in his father and no one else in the family is known to be affected. Which of the following modes of inheritance is least likely?
- Autosomal recessive
- Autosomal dominant
- X-linked recessive
- Sex-linked dominant
Which of the following cloning vectors is designed to accommodate the largest size DNA insert?
- YAC
- Plasmid
- Phage
- Cosmid
Which of the following explanations about a dominant genetic trait subject to genomic imprinting is FALSE?
- In a given family, only males or females will be affected.
- The trait may appear to skip generations.
- Affected individuals will always inherit the mutation from either the mother or father, but not both.
- Severity of the phenotype will be independent of sex of the affected individual.
Which of the following explanations about restriction endonucleases is FALSE?
- The enzymes are natural products of bacteria.
- The enzymes cut DNA at defined sequences.
- The enzymes cut only single-stranded DNA molecules.
- The enzymes are named because they restrict the growth of bacteriophage.
The basis for the current treatment of urea cycle disorder is
- replacement of missing enzyme activity by enzyme infusion
- providing alternative pathways for excretion of ammonia
- coenzyme replacement
- kidney transplant
Which of the following represents the clones of a cDNA library?
- mRNA
- Genomic DNA
- Intron
- Exons
Which of the following is involved in targeting enzymes to the lysosome?
- Mannose-6-phosphate
- Phosphorylation of tyrosine
- Cleavage of N-terminus of protein
- Cleavage of C-terminus of protein
Which of the following inborn errors of metabolism can be treated by enzyme infusion?
- Galactosemia
- Dihydropteridine reductase (DHPR) deficiency
- Canavan disease
- Gaucher disease
Which of the following defines a sequence in dysmorphology?
- Multiple anomalies attributed to mutation in a specific gene.
- Non-random happening of multiple anomalies is more frequent than expected by chance.
- Set of anomalies that can be attributed to consequences of a single aberrant developmental event.
- Set of anomalies resulting from damage to a fetal structure.
Developmental anomalies associated with basal cell nevus syndrome are believed to occur as a result of
- homozygous mutation of a tumor suppressor gene
- gain of function mutation
- haploinsufficiency
- loss-of-function mutation
Failure to produce Mullerian-inhibiting substance in a human male would result in
- deficit of formation of a testis
- breast development in human males at puberty
- deficit of virilization of the phallus
- presence of a uterus
Hox genes encode proteins with which of the following properties?
- Presence of DNA-binding domain
- Transport to lysosome
- Binding of extracellular ligands in the cell membrane
- Secretion from the cell
Which of the following would most likely explain a 46, XX individual with development of testes?
- Mutation of SOX9 gene
- Presence of excessive androgen during in utero development
- Translocation of SRY from the Y to an autosome
- Chimerism with a 46, XY cell line
Cirrhosis occurring in a 25 year woman suffering from thalassemia would be a consequence of
- iron overload
- toxicity due to chelation therapy
- hepatitis infection due to transfusion
- chronic anemia
The high prevalence of beta thalassemia mutation in Sardinia is best attributed to
- heterozygote advantage
- high mutation rate
- genetic drift
- low frequency of consanguinity
Tay-Sachs disease carrier screening is most commonly done by
- enzyme assay
- DNA-based testing
- ophthalmological testing searching for a cherry-red spot
- analysis of a blood smear
A major limitation of DNA-based carrier screening in cystic fibrosis is
- germline mosaicism
- laboratory errors in mutation analysis
- negative carrier testing
- incomplete ascertainment of mutations
The most significant limitation of molecular analysis of the HFE gene for screening for hemochromatosis in individuals of northern European descent is
- non-penetrance
- allelic heterogeneity
- genetic heterogeneity
- locus heterogeneity