考前思考题.doc

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1、（摘自 45 度角 F3 http:/www.cc98.org/dispbbs.asp?BoardID=241 the fragments were separated by electrophoresis and then transferred to a membrane filter using the Southern blot technique. The blots were probed with a particular cloned sequence. Three different patters of hybridization were seen on the blot

2、s. Some DNA samples (56 of them) showed a single band of 6.3kb, others (6) showed a single band of 4.1kb, and others (38) showed both the 6.3-and the 4.1-kb bands.a. Interpret these results in terms of BamHsites.b. What are the frequencies of the restriction site allele?c. Does this population appea

3、r to be in Hardy-Weinberg equilibrium for the relevant restriction site?2It is possible to create a zygote from two copies of the maternal genome alone. In amphibians, the zygote will develop and mature into an adult without fertilization by a sperm cell (this process is known parthenogenesis). The

4、same experiment has been attempted in mice, but it always results in early prenatal death. Explain this.3. Explain why 8% to 10% of female carriers of the DMD gene have muscle weakness or DMD phenotype.4. One member of a pair of MZ twins is affected by an autosomal dominant disease, and the other is

5、 not. List two different ways in which this could happen.5. The G6PD locus is located on the X chromosome. Studies of G6PD alleles in tumor cells from women show that all tumor cells usually express the same single G6PD allele, even though the women are heterozygous at the G6PD locus. What does this

6、 finding imply about the origin of the tumor cells?6. A pedigree for an autosomal dominant disease, each family member has been typed for a four-allele microsatellite marker, as shown in the aoutradiogram below the pedigree. Determine linkage phase for the disease and marker locus in the affected ma

7、le in generation . Based on the meioses that produced the offspring in generation , what is the recombination frequency for the marker and disease locus?7. Figure out the all possible offsprings from the couple which female with balanced reciprocal translocation of XX, t (2; 5) (q21; q31) and male w

8、ith normal male karyotype after reading something. (only list zygote karyotype)8. DMD has a high mutation rate but shows no ethnic variation in frequency. Use your knowledge of the gene and the genetics of DMD to suggest why this disorder is equally common in all populations.9. Inversions are known

9、to affect crossing-over. The following homologs have the indicated gene order (the filled and open circles are homologous centromeres): a. Considering the position of the centromere, what is this sort of inversion called?b. Diagram the alignment of these chromosomes during meiosis.c. Diagram the res

10、ult of a single crossover between homologous genes B and C in the inversion. 10. Alzheimer disease (AD) is the leading cause of dementia in old adults. Evidence that genetic alterations are involved in AD comes from three sources; the incidence of AD in first-degree relatives, the incidence in pairs

11、 if twins, and pedigree analysis. There is a 24-50 percent risk of AD by age 90 in first-degree relatives of individuals with AD, a 40-50 percent risk of AD in the identical(monozygotic) twin of individual with AD, and a 10-50 percent risk of AD in the fraternal (dizygotic) twin of individual with A

12、D. Individuals with AD in a subset of families showing AD have an alteration in the APP (amyloid protein) gene on chromosome 21. Individuals with AD in another subset of AD families have particular allele (E4) at the APOE (apolipoprotein E) gene on chromosome 19. Individuals homozygous for the E4 al

13、lele have increased risk of AD and earlier disease onset than heterozygotes. Population studies have shown that 40-50 percent of AD cases are associated with alterations in the APOE gene, but less than 1 percent of AD cases are associated with mutations in the APP gene.a. In what sense might AD be c

14、onsidered a polygentic trait?b. If AD has a genetic basis, why are identical twins not equally affected?11. Rearrangement at the end of 16p (the short arm of chromosome 16) underlie a variety of common human genetic disorders, including -thalassemia (a defect in hemoglobin metabolism caused by mutat

15、ions in the -globin gene), mental retardation, and the adult form of polycystic kidney disease. The availability of approximately 285-kilobase (kb) pairs of DNA sequence at the end of human chromosome 16p has allowed very detailed analysis of the structure of this chromosome region. The first functi

16、onal gene lies about 44 kb from the region of simple telomeric sequences and about 8 kb from the telomere-associated sequences. Analysis of sequences proximal (nearer the centromere) to the first gene reveals a sinusoidal variation in GC content, with GC-rich regions associated with gene-rich areas

17、and AT-rich regions associated with Alu-dense areas. The- globin gene lies about 130 kb from telomere-associated sequences.a. Discuss these findings in light of the current view of telomere structure and function as presented in the text.b. What new information have the preceding data revealed about the distribution of SINEs in the terminus of 16p? (SINs and LINs are, respectively, short and long interspersed nuclear elements.)