Saturday, 2 March 2013

Multiple choice questions in genetics

1. Which of the following chromosomal alterations would you expect to have the most drastic consequences?
(a) inversion (b) duplication
(c) translocation (d) deletion
2. The most common lethal genetic disease in the United States is
(a) sickle-cell an emia (b) cystic fibrosis
(c) Huntington’s disease (d) hemophilia.
3. There are various procedures that can be used to detect genetic disorders before birth. Among the tests discussed in this chapter, ____ is the least invasive, while ____ carries the highest risk.
(a) chorionic villi sampling . . . amniocentesis
(b) ultrasound imaging . . . fetoscopy
(c) fetoscopy . . . chorionic villi sampling
(d) fetoscopy . . . amniocentesis
4. Tay-Sachs disease runs in Seema’s family. On a family pedigree, she saw a half darkened circle. This represented
(a) a male with Tay-Sachs (b) a female with Tay-Sachs
(c) a carrier male (d) a carrier female.
5. On a pedigree tracing the inheritance of PKU, a horizontal line joins a black square and a half-black circle. What fraction of this couple’s children would you expect to suffer from PKU?
(a) none (b) 1/4
(c) 1/2 (d) 3/4
6. Ram and Nidhi are apparently normal, but their daughter was born with alkaptonuria, an inherited metabolic disorder. If alkaptonuria is like most human hereditary disorders, the probability of their next child being born with alkaptonuria is
(a) 0 (b) 1/4
(c) 1/2 (d) 2/3
7. Several inherited disorders are much more common in close-knit religious communities, such as the Amish(Jews), than in the general population. This is at least partly due to the fact that
(a) people in such communities are more likely to marry relatives
(b) shared environmental conditions such as diet can increase mutation rate
(c) modern medical care is not widely available in such communities
(d) community members care for each other and disorders are possed on.
8. A heritable feature is a ______ and may have two or more variants called______ .
(a) trait/characteristics (b) character/traits
(c) character/factors (d) trait/factors
9. In a cross between two heterozygotes (Aa), the F2 generation will be
(a) in the ratio 1:3 heterozygous to homozygous
(b) all heterozygous
(c) in the ratio 1:1 homozygous to heterozygous
(d) in the ratio 1:3 homozygous to heterozygous
10. You set up an experiment in which you breed two populations of true-breeding pea plants. The first true-breeding population has yellow round seeds and the second has green wrinkled seeds. All of the F1 plants yield yellow round seeds. When you self fertilize the F1 the F2 generation yields a mixture of yellow round, yellow wrinkled, green round and green wrinkled seeds. What does this tell you about the alleles for seed color and shape?
(a) the recessive alleles are always expressed
(b) the alleles are on different chromosomes
(c) the two alleles for each character segregate during gamete production
(d) both genes are on the same chromosome
11. You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parent traits?
(a) red and white are codominant
(b) red is dominant
(c) both red and white are recessive
(d) red and white show incomplete dominance
12. While on a field trip in the jungle you find a new species of mouse. You catch a pair and take them back to the lab. In mice, black coat color, B, is dominant to brown b,yet the female mouse gives rise to a large litter in which 9 of the offspring were black, 3 were brown and 4 were white. You conclude that
(a) a new mutation has occurred in the mice
(b) this is an example of polygenic inheritance
(c) there must be an epistatic interaction influencing coat color
(d) the coat color alleles are codominant
13. A new breed of domestic cat, the Indian Curl Cat, has unusual curled-back ears.When the owners of Shulamith, the foundation cat from which the breed arose, crossed her with a normal straight-eared domestic cat in each of her litters roughly half of the kittens had curled ears. When both parents are curl cats, all the kittens have curled ears. What does this tell you about the curled-ear trait?
(a) curled ears and straight ears are codominant traits
(b) curled ears and straight ears are show incomplete dominance
(c) curled ears are dominant
(d) curled ears are recessive
14. John and Jesica are planning a family, but since each has a brother who has sicklecell anemia, they are concerned that their children may develop sickle-cell disease.Neither John, Jane nor their respective parents have the disease. They consult agenetic counselor who tells them
(a) there is very little chance that any of their children will have sickle-cell disease
(b) that all of their children will have sickle-cell disease
(c) that one out of four of their children could be expected to have sickle cell-disease
(d) that its possible that none of their children will have the disease but blood tests on them both will be required to make sure
15. Why is sickle cell disease so called?
(a) because it makes people sick
(b) its named after a special type of white blood cell
(c) pH changes in the blood cells make them collapse into a sickle shape
(d) because its caused by an infectious microorganism that has sickle shaped cells
16. In people with sickle cell disease the red blood cells breakdown, clump, and clog the blood vessels. The broken cells accumulate in the spleen. Among other things this leads to physical weakness, heart failure, pain, brain damage and spleen damage. Affected individuals become paralyzed and can develop rheumatism, pneumonia and other diseases and kidney failure. This is an example of
(a) the polygenic nature of sickle cell disease
(b) the pleiotropic effects of the sickle cell allele
(c) an epistatic interaction between the sickle cell allele and a proteolytic enzyme gene
(d) infectious organisms acting on the sickle cell allele
17. Heart disease, diabetes, cancer, alcoholism and many mental illnesses can best be described as:
(a) symptoms of a bad life-style
(b) infectious diseases caused by microorganisms
(c) multifactorial disorders with a possible polygenic component
(d) all symptoms of Huntingdon’s disease
18. The genetic disease cystic fibrosis is caused by a defective allele that
(a) produces a dysfunctional enzyme that fails to break down brain lipids.
(b) causes hemoglobin molecules to collapse.
(c) produces a defective chlorine-channel membrane transport protein.
(d) produces a neurotoxin
19. Huntington’s disease is an example of a genetic disorder caused by
(a) a late-acting lethal dominant allele
(b) a non-lethal dominant allele
(c) a late acting recessive allele
(d) homozygous recessive alleles
20. Which of the following is a form of sexual reproduction?
(a) budding (b) fission
(c) hermaphroditism (d) regeneration
21. The most common phenotype in a natural population is referred to as the
(a) genotype (b) wild type
(c) autosome (d) mutant phenotype
22. Human males are much more likely to be have hemophilia (a failure of blood to clot properly) than human females. This is the case because
(a) hemophilia is a contagious disease to which males are more susceptible
(b) the gene for hemophilia is carried on the Y chromosome
(c) hemophilia is carried on the autosomes
(d) the gene for hemophilia is sex-linked
23. In a particular species of mammal black hair (B) is dominant to green hair (b) and red eyes (R) are dominant to white eyes (r). If a BbRr individual is mated with a bbrr individual the expected phenotypic ratio of the offspring is 1 black-red : 1 black-white: 1 green-red : 1 green-white. However, when you mate these individuals you find that the phenotypic ratio of the offspring is 6 black-red : 1 black-white : 1 green-red : 6 green-white. What could account for this difference?
(a) The genes for hair color and the genes for eye color are carried on different chromosomes
(b) The expected results did not take genetic recombination into account
(c) The genes for hair color and eye color are linked
(d) The genes for hair color and eye color show dependent assortment
24. In the problem no. 23 the observed F2 generation distribution of offspring was: blackred 1,070; black-white 177; green-red 180; green-white1072. Based on this data, what is the recombination frequency ?
(a) 30 percent (b) 7 percent
(c) 17 percent (d) 14 percent
25. How many map units is a recombination frequency of 5 percent equal to?
(a) 2.5 centimorgans (b) 10 centimorgans
(c) 5 centisturtevants (d) 5 centimorgans
26. A linkage map
(a) orders genes on a chromosome based on recombination frequencies
(b) can only be constructed for sex chromosomes
(c) orders genes on a chromosome based on their location with respect to a stained band
(d) shows the actual ordering and spacing of genes on a chromosome
27. A male bee is
(a) X Y (b) diploid
(c) hapliod (d) Z W
28. What is the probability that a male will inherit an X-linked recessive gene from his father?
(a) 0 (b) 25 percent
(c) 50 percent (d) 75 percent
29. Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls?
(a) Sex-linked traits are never seen in girls
(b) The allele is carried on the Y chromosome
(c) Nondisjunction occurs in males but not in females
(d) In order to express an X-linked recessive, a female must have two copies of the gene
30. Which of the following human genetic disorders is sex linked?
(a) hemophilia (b) PKU
(c) cystic fibrosis (d) achondroplasia
31. A genetic defect in humans results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way. A woman with this defect typically has small patches of skin with sweat glands and other patches where sweat glands are lacking. This pattern suggests the phenotypic effect of
(a) a mutation
(b) chromosome inactivation
(c) RNA splicing
(d) an operon
32. Which of the following is correct with regard to aneuploidy?
(a) inversion
(b) 2n + 1
(c) All aneuploid individuals die before birth
(d) 4n
33. If a fragment of a chromosome breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called
(a) a deletion (b) an inversion
(c) a translocation (d) a nondisjunction
34. Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?
(a) There are probably more genes on chromosome 21 than on the others
(b) Chromosome 21 is a sex chromosome and 3 and 16 are not
(c) Down syndrome is not more common, just more serious
(d) Extra copies of the other chromosomes are probably fatal
35. Humans have 23 pairs of chromosomes, while our closest relatives, chimpanzees, have 24. Chromosome studies indicate that at some point early in human evolution, two chromosomes simultaneously broke into a large portion and a small portion. The large parts combined to form a large chromosome, and the small parts combined to form a much smaller chromosome (which was subsequently lost). This important chromosomal change could best be described as
(a) nondisjunction followed by deletion
(b) translocation followed by deletion
(c) duplication followed by deletion
(d) translocation followed by inversion
36. Each cell in an individual with Down syndrome contains ____ chromosomes.
(a) 47 (b) 22
(c) 24 (d) 45
37. Disorders involving unusual numbers of sex chromosomes show that maleness is caused by the
(a) presence of an X chromosome
(b) presence of a Y chromosome
(c) absence of an X chromosome
(d) absence of a Y chromosome
38. A particular allele can have different effects if it was inherited from a male rather than a female. This phenomenon is known as
(a) extranuclear inheritance
(b) genome imprinting
(c) sex-linkage
(d) Prader-Willi syndrome
39. Human mitochondria
(a) are inherited as an X-linked trait
(b) are all inherited from the father
(c) have linear DNA
(d) are all inherited from the mother
40. Both chloroplasts and mitochondria
(a) are found within the nucleus
(b) have linear DNA
(c) carry extranuclear genes
(d) display a Mendelian pattern of inheritance
41. Who demonstrated that genes are located on chromosomes?
(a) Morgan (b) Meselson and Stahl
(c) Chargaff (d) Franklin
42. In Griffith’s experiments, a harmless variant of S. pneumoniae became pathogenic when mixed with a heat-killed pathogenic variant as a result of
(a) conjugation (b) transduction
(c) mutation (d) transformation
43. In an important experiment, bacteriophages were allowed to infect bacteria. In the first trial, the phages used contained radioactive DNA, and radioactivity was detected in the bacteria. Next, other phages containing radioactive protein were allowed to infect bacteria, and no radioactivity was detected in the bacteria. When the experimenters compared the results of these two trials, they concluded that
(a) genes are made of DNA
(b) bacteriophages can infect bacteria
(c) DNA is made of nucleotides
(d) genes carry information for making proteins
44. A geneticist raised a crop of T2 bacteriophages in a medium containing radioactive phosphorus, so that the DNA of the bacteriophages was labeled with radioactivity. The labeled phages were then allowed to infect nonradioactive bacteria. In a few hours, these bacteria burst open, releasing many bacteriophages. Some of these phages contained labeled
(a) DNA
(b) RNA
(c) protein
(d) DNA and protein only
45. Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have
(a) the protein of T2 and the DNA of T4
(b) the protein of T4 and the DNA of T2
(c) the protein and DNA of T2
(d) the protein and DNA of T4
46. Chargaff found that for DNA
(a) the ratio of A to C is close to 1:1 and the ratio of G to T is close to 1:1
(b) the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
(c) the ratio of A to G is close to 1:1 and the ratio of T to C is close to 1:1
(d) A + T = G + C
47. The X-ray diffraction studies conducted by ______ were key to the discovery of the
structure of DNA.
(a) McClintock (b) Franklin
(c) Meselson and Stahl (d) Chargaff
48. Which of the following is not true of DNA?
(a) A pairs with T and G pairs with C
(b) Nitrogen bases are 0.34 nm apart on a DNA strand
(c) The double helix is 2.0 nm wide
(d) The double helix is 3.4 nm wide
49. Which of the following is correct?
(a) A forms 2 hydrogen bonds with G; T forms 3 hydrogen bonds with C
(b) A forms 3 hydrogen bonds with T; G forms 2 hydrogen bonds with C
(c) A forms 2 covalent bonds with T; G forms 3 covalent bonds with C
(d) A forms 2 hydrogen bonds with T; G forms 3 hydrogen bonds with C
50. Which of the following is not needed for DNA replication?
(a) ribosomes (b) DNA
(c) nucleotides (d) enzymes
1. (d) 2. (b) 3. (b) 4. (d) 5. (c) 6. (b) 7. (a) 8. (b) 9. (c) 10. (c)
11. (d) 12. (c) 13. (c) 14. (d) 15. (c) 16. (b) 17. (c) 18. (c) 19. (a) 20. (c)
21. (b) 22. (d) 23. (c) 24. (d) 25. (d) 26. (a) 27. (c) 28. (a) 29. (d) 30. (a)
31. (b) 32. (b) 33. (b) 34. (d) 35. (b) 36. (a) 37. (b) 38. (b) 39. (d) 40. (c)
41. (a) 42. (d) 43. (a) 44. (a) 45. (d) 46. (b) 47. (b) 48. (d) 49. (d) 50. (a)

1 comment: