mcq@genetics&biochemistry

1. Patients with Hurler’ s syndrome (252800) are known to have mutations
at the L-iduronidase locus. The diagnosis of Hurler’ s syndrome is most effi-
ciently made by analyzing a patient’ s DNA for
a.A region of DNA that does not encode RNA  b.Alternative forms of the L-iduronidase gene
c.The entire set of genes in one leukocyte d.A nucleotide substitution in the L-iduronidase gene
e.The position of the L-iduronidase gene on a chromosome

2. Which of the following statements regarding a double-helical molecule of DNA is true?
a.All hydroxyl groups of pentoses are involved in linkages b.Bases are perpendicular to the axis
c.Each strand is identical d.Each strand has parallel, 5′ to 3′ direction e.Each strand replicates itself

3. A sample of human DNA is subjected to increasing temperature until the major fraction exhibits optical density changes due to disruption of its helix (melting or denaturation). A smaller fraction is atypical in that it requires a much higher temperature for melting. This smaller, atypical frac- tion of DNA must contain a higher content of
a.Adenine plus cytosine b.Cytosine plus guanine c.Adenine plus thymine d.Cytosine plus thymine e.Adenine plus guanine.

4. A newborn baby has a sibling with sickle cell anemia (141900) and is at risk for the disease. The appropriate diagnostic test for sickle cell anemia in this baby will include
a.DNA amplification b.Hemoglobin antibodies c.DNA restriction d.Red cell counting e.DNA fingerprinting
 
5. A polymorphism is best defined as
a.Cosegregation of alleles b.One phenotype, multiple genotypes c.Nonrandom allele association d.One locus, multiple abnormal alleles e.One locus, multiple normal alleles

6. The process that occurs at the 5 position of cytidine and often correlates with gene inactivation is
a.Gene conversion b.Sister chromatid exchange c.Pseudogene d.Gene rearrangement e.DNA methylation

7. The average size of a human gene is
a.1,000 bp b.40,000 bp c.2 × 106 bp d.1.5 × 108bp e.3 × 109bp

8. Restriction fragment length polymorphism (RFLP) analysis can only be used to follow the inheritance of a genetic disease if
a.mRNA probes are used in combination with antibodies
b.The disease-causing mutation is at or closely linked to an altered restriction site
c.Proteins of mutated and normal genes migrate differently upon gel electrophoresis
d.Mutations are outside of restriction sites so that cleaving still occurs
e.Restriction fragments remain the same size but their charge changes