遺傳學(xué)測試題：7-期中測試

1、1. Wich of the following best explains variable expression in mitochondrial diseases?(2.0分)A.modifier lociB.heterozygosityC. heteroplasmy D. locus heterogeneity E.imprinting2. Some autosomal recessive diseases have a high prevalence in large populations, even though they are often fatal (e.g., sickl

2、e cell disease in Africans, cystic fibrosis in Europeans). Which of the following is the most likely explanation for this phenomeno(2.0分)A.Survival advantage in individuals who are normal homozygotesB.High mutation rates in specific populationsC.Survival advantage in heterozygous carriersD.Inbreedin

3、gE.None of the above mechanisms explain the pattern3. You would be likely to observe the lowest heritability score in (2.0分)A. MumpsB.Spina bifida C.Cleft lip/palateD.Cystic fibrosis E.Congenital heart disease4. Which of the following would you not expect to see in a typical multifactorial disorder?

4、(2.0分)A.Sibling recurrence risk of 50%B.Rapid decrease of recurrence risk with more remote degrees of relationshipC.Co-occurrence of the disorder in fathers and sonsD. Positive correlation between prevalence of the disorder in the population and sibling recurrence riskE.Higher concordance in monozyg

5、otic twins than in dizygotic twins5. Which of the following diseases is a good example of locus heterogeneity? (2.0分)A.Duchenne muscular dystrophyB.Myotonic dystrophyC.Osteogenesis imperfecta D.Prader-Willi syndrome E.Hemophilia A6. Mutations in fibrillin gene can cause(2.0分)A.Huntington diseaseB.Ac

6、hondroplasiaC.Neurofibromatosis type 1D.Retinoblastoma E.Marfan syndrome7. Bob has hypophosphatemic rickets（低磷酸鹽血癥）. He and his wife Jill come to the genetics for counseling because they would like to have children. What can you tell them about the likelihood that any daughters will be affected? Any

7、 sons?(2.0分)A.0% daughters, 100% sons B.50% daughters, 100% sonsC.100% daughters, 50% sons D.100% daughters, 0% sons8. Your patient is a 5-year-old girl who appears to have Duchenne muscular dystrophy. What is the most likely genetic explanation for this disease in a girl?(2.0分)A.She has a dominant

8、negative mutation. B.She has skewed（偏離的；傾斜的）X inactivation.C.She has two independent DMD mutations.D.She has a 46, XY karyotype with sex reversal.E.This diagnosis is impossible.9. Which of the following properties would a single nucleotide polymorphism (SNP) have to be detected by Southern blot?(2.0

9、分)A.It must be a nonsense mutationB.It must alter a splice site C.It must alter a restriction site D.It must alter the encoded amino acid sequence E. It must alter the stability of the encoded mRNA10. Which of the following could produce an XY female?(2.0分)A.Translocation of the Sry gene to the X ch

10、romosome during meiosis in the fatherB.Point mutation in the Sry geneC.Deletion of the Sry geneD.All of the above11. Which of the following statements is incorrect regarding the recurrence risk of multifactorial inherited disorders(2.0分)A.The risk for their children gets higher when the patients are

11、 seriously affectedB.The risk gets higher when the degree of relationship increasesC.The risk gets higher when the number of patients in the family increaseD.The risk gets higher when one or both parents are affected12. A man who is affected with hemophilia A (X-linked recessive) mates with a woman

12、who is a heterozygous carrier of this disorder. What proportion of this couple's daughters will be affected ? (2.0分)A.0.75B.0.25C.0.5D.113. The correct number of 46 human chromosomes was discovered by(2.0分)A.Caspersson B.MorganC.Tjio and Levan D.Mendel E.Watson14. Differences between male a

13、nd female meiosis include:(2.0分)A. All of the aboveB.Female meiosis begins prenatally but arrests in dictyotene until each menstrual cycleC.Meiosis in females requires fertilization for completionD.4 vs. 1 gametes generated per meiosisE. None of the above15. Relative to nuclear DNA, the mutation rat

14、e of midochondrial DNA is:, XX/45, X表明為：(2.0分)A. Higher, due to limitations in DNA repair capabilities B.Apparently lower, due to the number of copies of mtDNA per cell C.Approximately equal D.Lower, due to protection of the mitochondria from environmental insults16. Coding strand(2.5分)Strand of gen

15、omic DNA to which the mRNA is identical. Untranscribed strand of the gene (5to 3) is called as “coding” or “sense” for the corresponding codes in RNA.17. Gene pool(2.5分)the genetic constitution of a population of a given organism. All the genes of all the individuals in population make up the gene p

16、ool.18. SNP(2.5分)A change in which a single base in the DNA differs from the usual base at that position.19. HapMap(2.5分)A set of haplotypes, defined by tag SNPs, distributed throughout the genome, used for association studies20. 同義突變和無義突變(5.0分)Silent mutations are DNA mutations that do not result i

17、n a change to the amino acid sequence of a protein nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product.21. 常染色體和常染色質(zhì)(5.0分)Autosome: an

18、y chromosome that is not a sex chromosome; appear in pairs in body cells but as single chromosomes in gametesEuchromatin: slightly and evenly stained, non- or low-repetitive DNA regions, the major component of chromatin.22. 單倍體和單倍型(5.0分)Haploid: an organism or cell having only one complete set of ch

19、romosomesHaplotype: a group of alleles in coupling at closely linked loci, usually inherited as a unit.23. 基因組和基因庫(5.0分)Genome: the complete DNA sequence, containing the entire genetic information ,of a gamete ,an individual ,a population or a species.Gene pool: The genetic constitution of a populat

20、ion of a given organism. All the genes of all the individuals in population make up the gene pool.24. You are asked to see a child with hereditary tyrosinemia, an autosomal recessive disorder of amino acid metabolism that causes liver failure. Both parents are of French Canadian ancestry, and come f

21、rom a region of Quebec where 1:1600 newborns are affected with tyrosinemia. What is the carrier frequency of tyrosinemia in this region? You learn that 90% of mutations responsible for tyrosinemia in this population consist of the same single base change. This mutation is much less common elsewhere

22、in the world. What is most likely to account for the high frequency of this mutation in a small region in Quebec?(10.0分)Lets assume that two alleles are A and a , p and q represent the gene frequency respectively.Since the inheritance pattern for the disease is autosomal recessive , and frequencies

23、of the affected among Quebec population is 1:1600, We can see: q is 1/40;thus p=1-q=39/40 frequency of carriers is 2pq=2*1/40*39/40=78/1600; conclusion: probability of next generation having the disorder is 1/4 in this family and for population is 78/1600*78/1600*1/4=0.05%25. What is the parental or

24、igin of the extra chromosome in the Down syndrome child below, and was the error in meiosisor meiosis  (5.0分)the extra 21 chromosome must come from her father. The error happened in meiosis 2.26. Duchenne muscular dystrophy is sex-linked and usually affects only males. Victims of the disease become progressively weaker, starting early in life. a. What is the probability that a woman whose brother has the disease will have an affected child? b. If  b. If your mother's brother (your uncle) had Duchenne's disease, what is the probability that you have received the allele