8-肿瘤遗传学——done

1. 癌基因在细胞水平呈（），一个等位基因的突变足以使正常细胞发生恶变。Ras蛋白是一个位于细胞膜内部，存在于细胞膜上信号转导蛋白。当它被细胞外因子激活时，便会从GDP状态变为有活性的GTP状态，产生刺激细胞生长的信号。而突变的Ras蛋白始终处于被激活的GTP活性状态。现已在许多肿瘤中发现了ras 基因的点突变。(6.0分)

A.不规则显性

B.共显性

C.中间显性

D.显性

E.延迟显性

2. 尽管在大多数情况下，这些家族性肿瘤呈常染色体显性遗传，但其发生需要相应的肿瘤抑制基因的基因座上两个等位基因的（）。(6.0分)

A.相互融合

B.一个扩增

C.全部扩增

D.一个失活

E.全部失活

3. Dara is a 40 year-old woman who has just been found to have breast cancer. Because of additional family history of breast cancer, her sisters are concerned that an inherited mutation is responsible for the cancer. A clinical geneticist discusses these concerns with the family and they decide to proceed with genetic testing. What type of sample would she get from Dara’s do ctor to do this testing?(8.0分)

A.Bone marrow

B.White blood cells

C.Red blood cells

D.Biopsy of the tumor

E.Cell line from the tumor

4. Which of the following types of mutations would you expect to cause cancer when it occurs in an oncogene?(8.0分)

A.A or B

B.A gain of function mutation

C.Gene amplification

D.A loss of function mutation

E.B or C

5. Jill is concerned about her risk of hereditary breast cancer. Which of the following family histories would be most likely to be associated with a germline mutation that would predispose Jill to breast cancer(If she inherited that mutation)?(8.0分)

A.Breast cancer in Jill's paternal aunt at age 55 years and prostate

cancer in her father at age 62 years

B. Breast cancer in Jilil's mother at age 60 years

C. Breast cancer in Jill's paternal grandmother at age 60 years and

in her maternal grandmother at age 62 years

D. Breast cancer in Jill's paternal aunt at age 40 years and in her

paternal grandmother at age 45 years

E.Breast cancer in Jill's mother at age 60 years and prostate cancer

in her father at age 62 years

6. A 4-year old girl is seen by a dermatologist.The child has fair skin with many freckled areas and is very sensitive to light.She sunburns easily and does not like to play outdoors.Some of her freckled areas seem large and one is irritated.A defect in which DNA repair process is most likely the cause of her photosensitivity? (8.0分)

A.Nucleotide excision repair.

B.Mismatch repair

C.Non-homologous end joining

D.Base excision repair

E.SOS repair

7. A colonoscopy on a 20-year-old man reveals several hundred growths on the epithelial surface of the large bowel. Histologic examination of biopsied tissue revealed mild to moderate cellular dysplasia. DNA analysis is most likely to reveal a mutation in which gene? (8.0分)

A.RAS

B.DCC

C.MLH1

D.APC

E.TP53

8. Jack’s father and son were both affected by retinoblastoma when they were children, but Jack himself was not.Which of the following is the most likely explanation for the incomplete penetrance of the RB mutation in Jack, who is an obligate carrier of the mutation? (8.0分)

A.Jack carries a duplication of his wild-type copy of RB

B.A spontaneous reversion of the RB mutation occurred early in Jack’s

development

C.Jack inherited a second site mutation that counteracts the RB

mutation

D.No somatic mutation in RB occurred in any of Jack’s retinal cells

E.Jack carries a somatic deletion of the mutant RB allele

9. Thus far, two genes have been found that can cause autosomal dominant breast cancer (one on chromosome 13 and one on chromosome 17).This is best described as an example of: (8.0分)

A.Linkage disequilibrium

B.Allelic heterogeneity

C.Synteny

D.Linkage

E.Locus heterogeneity

10. Autosomal dominant breast cancer caused by mutations in the BRCA1 gene (chromosome 17) is characterized by:(8.0分)

A.increased risk of small cell lung cancer

B.increased incidence of breast cancer in males

C.increased risk of ovarian cancer

D.relatively early age of onset of the disease

E.A and C

11. Which of the following is true of autosomal dominant breast cancer?(8.0分)

A.Penetrance is close to 100%, with nearly all gene carriers

developing breast cancer by age 80

B.It accounts for nearly half of all breast cancer cases in the United

States

C.It can be detected by hybridization with a single oligonucleotide

probe

D.It is characterized by locus heterogeneity

E.Autosomal dominant breast cancer affects females but not males

12. Concerning retinoblastoma, which of the following is not predicted by the two-hit model? (8.0分)

A.two copies of the gene must be disabled for tumor expression to occur

B.inherited tumors will be multifocal

C.penetrance is incomplete

D.sporadic tumors will be unifocal

E.imprinting will be observed

13. Phosphorylation of gene product by cyclin-dependent kinases (CDK); binding of gene product to transcription factors such as E2F (8.0分)

A.Huntington disease

B.Achondroplasia

C.Neurofibromatosis type 1

D.Retinoblastoma

E.Marfan syndrome