Medical Genetics
Comprehensive test covering cancer genetics, genetic counseling, metabolic disorders, molecular diagnostics, chromosomal abnormalities, and population genetics for medical students and aspirants.
Questions
Microsatellite instability concerns with
- Hereditary nonpolyposis colon cancer
- Familial adenomatous polyposis
- Neurofibromatosis
- Hereditary breast cancer
Genes responsible for hereditary nonpolyposis colon cancer encode proteins with which of the following functions?
- DNA mismatch repair
- Membrane receptors
- Transcription factors
- Cell cycle control
Response of non-small cell lung cancer to gefitinib is predicted by mutation in
- Abl oncogene
- Myc oncogene
- NF1 gene
- EGF receptor gene
Which among the following is a non-inherited genetic syndrome?
- Down syndrome
- Turner syndrome
- Deletion syndrome
- Williams syndrome
Which of the following measures clinical validity?
- The likelihood that a mutation stated to be present is in fact present.
- The likelihood that identification of a mutation correctly predicts presence or absence of disease.
- The likelihood that a mutation test will successfully identify a pathogenic mutation.
- The likelihood that an identified mutation is pathogenic vs. a benign variant.
Husband & wife present for counseling following three first trimester miscarriages. As part of their evaluation, both partners have chromosomal analysis. Husband is found to have the karyotype 46,XY,inv8(p13q23). What would you counsel them?
- This is a normal progeny likely of no significance.
- This is an abnormal chromosomal composition that would cause congenital anomalies if transmitted to a child.
- This rearrangement may lead to chromosomal imbalance in the offsprings and could explain multiple miscarriages in the female.
- This rearrangement may cause to dicentric or acentric chromosomes in the offsprings, which would probably not be appropriate with survival.
A couple decided to have an offspring and went to the genetic counselor. The lady told that her younger sister died in childhood with Down syndrome. There is no other family history of the condition. What is the most appropriate counseling?
- Down syndrome is generally random, so there is no increased risk to this couple.
- If results of the woman's sister's karyotype cannot be found, the woman herself should have chromosomal analysis.
- The pregnancy will be screened in the second trimester using alphafetoprotein, bhCG, and unconjugated estriol, which should be sufficient to detect Down syndrome if it has occurred.
- Prenatal diagnosis should be done by chorionic villus sampling or amniocentesis.
A 5 year old boy is found to have the karyotype 47, XXY. After being counseled about his diagnosis, his parents ask if he is at risk of passing this on to his son. What would you counsel them?
- There is a 50% risk that he will have a son with an extra X chromosome.
- He will be infertile so there is no risk of transmission.
- There is a slight possibility of fertility, and therefore he could have a chromosomally abnormal offspring.
- He will be unlikely to survive to reproductive age.
Which of the following inborn errors of metabolism can be treated by enzyme infusion?
- Dihydropteridine reductase deficiency
- Canavan disease
- Galactosemia
- Gaucher disease
A 3 year old girl with developmental delay is seen for evaluation. He has microcephaly, and his parents note that his birth weight was low. There is no known family history of similar problems. As routine karyotype is normal. His parents ask if there are additional cytogenetic tests that can be offered. What would you counsel them?
- A normal karyotype rules out all detectable chromosomal abnormalities.
- The girl should have FISH analysis for all known microdeletions.
- The chromosome study should be repeated in another laboratory.
- Analysis for subtelomere deletion may detect an abnormality missed by convential chromosomal analysis.
Which of the following involves in targeting the lysosomal enzymes?
- Mannose-6-phosphate
- Phosphorylation of tyrosine
- Cleavage of the N-terminus of the protein
- Cleavage of the C-terminus of the protein
Failure to generate Mullerian-inhibiting substance in a genetic male would lead in
- failure of formation of testes
- presence of a uterus
- breast development at puberty
- stoppage of virilization of phallus
Which of the following types of mutation would not be expected to detect in a molecular diagnostic test which is based on sequencing each exon of a gene in genomic DNA from a male suspected of having a X-linked disorder?
- Missense mutation
- Nonsense mutation
- Deletion of an exon
- Inversion of part of the gene
Which of the following would most likely explain a 46, XX individual with development of testes?
- Mutation of SOX9
- Presence of excessive androgen during in utero development
- Translocation of SRY from the Y to an autosome
- Chimerism with a 46, XY cell line
A couple seek molecular testing for prenatal diagnosis of an autosomal recessive condition. The haplotype in coupling with the mutation is found in both parents by analysis of the parents and the affected offsprings. Analysis of chorionic villus tissue from the embryo reveals that the embryo inherited only the maternal haplotype in coupling with the mutation. What would you counsel them?
- The developing embryo is most likely a carrier.
- The developing embryo could be affected if recombination occurred in the father.
- The developing embryo could be homozygous unaffected if recombination occurred in the mother.
- All of the above
The basis for the current treatment of urea cycle disorders is
- replacement of missing enzyme activity by enzyme infusion
- providing alternative pathways for excretion of ammonia
- coenzyme replacement
- kidney transplant
A sequence-based molecular diagnostic test reveals that an affected child has a missense mutation in a gene known to be associated with a dominantly-inherited disorder. The child is the first member of the family to be affected, and the disorder is associated with complete penetrance. The mutation has never been seen before, either in affected individuals or in controls. Which of the following would be the most powerful evidence that the mutation is pathogenic?
- Test both parents to see if the mutation is found only in the child.
- Determine whether the mutation affects an amino acid that is conserved in evolution.
- Examine the structure of the protein to see if the mutation has a major effect on protein function.
- Review the literature to see if the mutation has been reported to be pathogenic.
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
Developmental anomalies associated with basal cell nevus syndrome (BCNS) are believed to occur as a result of
- homozygous mutation of a tumor suppressor gene
- Haploinsufficiency
- Gain of function mutation
- Dominant negative effect
Tay-Sachs disease carrier screening is most commonly done by
- enzyme assay
- DNA-based testing
- analysis of a blood smear
- ophthalmological testing looking for a cherry-red spot
Which of the following is used as the mainstay of treatment of hemochromatosis?
- Transfusion
- Chelation
- Phlebotomy
- Iron
The high prevalence of beta thalassemia mutations in Sardinia is best attributed to
- high mutation rate
- heterozygote advantage
- genetic drift
- high frequency of consanguinity
Cirrhosis occurring in a male with thalassemia would be a result of
- iron overload
- chronic anemia
- toxicity due to chelation therapy
- hepatitis infection due to transfusion
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
- locus heterogeneity
- variable expression
Which of the following is a major limitation of DNA-based carrier screening in cystic fibrosis?
- Laboratory errors in mutation analysis
- Nonpenetrance of many CFTR mutations
- Germline mosaicism
- Incomplete ascertainment of mutations