Questions 1-20 are multiple choice. Pick one best answer. 1. Mutations near the carboxyl terminal of the procollagen 1 molecule (encoded by COLIAl) cause more severe symptoms than those in the amino terminal. This is an example of A. dominant negative mutation. B. locus heterogeneity. C. haplosufficiency. D. allelic heterogeneity. E. haploinsufficiency. 2. Which of the following could produce X Y females and XX males? A. Deletion of the SR Y gene. B. Point mutation in the SR Y gene. C. Insertion of the SR Y gene to the different region of Y chromosome in the father. D. Deletion of the Y chromosome. E. Translocation of the SR Y gene to the X chromosome during meiosis in the father. 3. In Sickle Cell Disease genotypes, while AA and A S are both phenotypically healthy, SS suffers from the disease. However, both A S and SS genotypes also produce sickle cells (sickle-shaped red blood cells) although A S also produces normal red blood cells. Which of the following best describes the relationship between A and S alleles? A. A is dominant to S in sickle cell production. B. A is dominant to S in sickle cell disease, but A and S are codominant in sickle cell production. C. A is dominant to S in sickle cell disease and in sickle cell production. D. A is dominant to S in sickle cell disease, but A is incompletely dominant to S in sickle cell production. E. A is dominant to S in sickle cell disease, but A is dominant to S in sickle cell production. 4. In -Thalassemia, nonsense or frameshift mutations can terminate translation in exon 3 of the -globin gene. The resulting mRNA produces unstable -globin chains. This destabilizes the normal -globin chains produced by the normal allele in heterozygotes. Consequently, heterozygotes become affected. This is an example of A. dominant mutation. B. haploinsufficiency. C. haplosufficiency. D. dominant negative mutation. E. missense mutation. 5. Rett Syndrome is X-linked dominant. Affected females tend to show variable expression of symptoms which also tend to be milder. This is because A. of X chromosome inactivation: cells with the normal recessive allele inactivated will express the dominant disease allele. B. of X chromosome inactivation: cells with the normal dominant allele inactivated will express the recessive disease allele. C. the disease is incomplete dominant in these females. D. these females just have an increased penetrance. E. these females suffer from Turner syndrome ( 45 , X ) , carrying only one X chromosome. 6. A phenotypically normal woman has had two children with Down syndrome. Which of the following scenarios would be most likely the cause? A. She is a germ-line mosaic for trisomy 13. B. She carries a Robertsonian translocation of chromosome 13 to chromosome 14. C. She carries a Robertsonian translocation of chromosome 22 to chromosome 14. D. She has had both children in her late 40 s. E. She carries a Robertsonian translocation of chromosome 13 to chromosome 15 . .