Medical Genetics Homework-1.doc
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1、Medical Genetics Homework-1Student Number: Name: . Pick the best answer and write in the corresponding blanks: 12345678910111213141516171819202122231. Contrasting genes at the same locus are called A. Homologus B. Alleles C. Allies D. Difactors E. Associates 2. One characteristic of a mutation is th
2、at it is A. Almost an improvement B. Genetically transmitted to future generations C. Always a dominant characteristic D. Limited to high organisms E. Prevented by using colchicine 3. Color blindness is more likely to occur in males than females because A. Males have a tendency to deposit cholestero
3、l in small blood vessels thereby reducing the oxygen and food supply to the retina B. Genes for the characteristic are located in sex chromosomes C. The trait is dominant in males and recessive in females D. Males require more vitamin A to achieve the same sensitivity in the rods and cones of the re
4、tina E. Some males have difficulty absorbing vitamin A, a necessary prerequisite to the synthesis of visual purple (rhodopsin) 4. If there is a large percentage of crossing-over between gene A and B, the explanation is that the genes are A. Located on separate chromosomes B. Located close together C
5、. Located far apart on the same chromosome D. Separated only by the centromere E. Connected by weak linkage 5. Mutt and Jeff are two brothers who were born with congenital deafness. Their parents had normal hearing. Mutt married Mabel. Mabel was also congenitally deaf and her parents had normal hear
6、ing. Mutt and Mabel had 10 children (5 boys and 5 girls) all of whom were born congenitally deaf. Jeff married Jane. Jane is not related to Mabel. Jane was congenitally deaf although her parents had normal hearing. Janes sister, Myrna, was also congenitally deaf. Jeff and Jane had 10 children (5 boy
7、s and 5 girls) none of whom were congenitally deaf. The probable explanation of the above pedigree is that: A. there is a single genetic locus with at least 2 different abnormal recessive alleles (a and b) which will result in congenital deafness when homozygous as either recessive aa, ab or bb. B.
8、there are at least 2 different genetic loci which have abnormal recessive alleles which will result in congenital deafness when both loci are homozygous for their abnormal alleles. C. there are at least 2 different genetic loci which have abnormal recessive alleles which will result in congenital de
9、afness when either locus is homozygous for its abnormal allele. D. Jeffs congenital deafness resulted from a spontaneous mutation and hence cannot be passed on. 6. Thus far, two genes have been found that can cause autosomal dominant breast cancer (one on chromosome 13 and one on chromosome 17). Thi
10、s is best described as an example of:A. Linkage B. Allelic heterogeneityC. Linkage disequilibrium D. Locus heterogeneity 7. Many biochemical defects, which are inherited in a single-gene Mendelian fashion, have multiple effects upon the individual affected. This phenomenon is known as:A. phenocopyin
11、g B. pleiotropy C. incomplete penetrance D. codominance 8. A young couple both affected with classical achondroplasia come to you for genetic counseling. There is no other family history of achondroplasia. You should inform them that if they have a tull term liveborn, the probabi1ity that the newbor
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