Genetics MCQ

Matching Questions Choose the one most appropriate answer for questions 49-51. 49. Colchicine __ 50. __ monosomy 51. _ _ trisomy a. inhibits microtubule assembly; prevents chromosome movement b. (2n - 1); a gamete deprived of a chromosome c. (2n + 1); three chromosomes of the same kind are present in a set of chromosomes

49. a 50. b 51. c

Choose the one most appropriate answer for questions 52-55. 52. deletion 53. __ duplication 54. _ _ inversion 55. translocation a. a chromosome segment is permanently transferred to a nonhomologous chromosome b. a repeat of a particular DNA sequence in the same chromosome or in nonhomologous ones c. a piece of the chromosome is inadvertently left out during the repair process d. a chromosome segment that has been cut out and rejoined at the same place, but backward

52. c 53. b 54. d 55. a

Match the cause of the disorder with the disorder for questions 56-60. . 56. Down syndrome 57. galactosemia and albinism 58. hemophilia and color blindness 59 Turner syndrome 60. Huntington's disease a. autosomal recessive inheritance b. nondisjunction of the twenty-first chromosomal pair c. X-linked recessive inheritance d. nondisjunction of the sex chromosomes e. Autosomal dominant inheritance

56. b 57. a 58. c 59. d 60. e

Different, or alternative, forms of the same gene are a) genetomorphs. b) alleles. c) mutants. d) chromatids. e) homologous.

B

Crossing over a) generally results in binary fission. b) involves centrioles. c) involves breakages and exchanges between sister chromatids. d) results in new combinations of alleles being channeled into the daughter cells. e) does all of these.

D

If meiosis did NOT occur in sexually reproducing organisms, a) growth of the zygote would be halted. b) mitosis would be sufficient. c) gametes would be haploid. d) the chromosome number would double in each generation. e) eggs would be haploid, but sperm would be diploid.

D

If short hair (L) is dominant to long hair (l), then what fraction of the offspring produced by a cross of Ll×ll will be homozygous dominant? a. 1/2 b. 1/4 c. 1/3 d. none (no chance of this offspring) e. none of these answers is correct

D

A human X-linked recessive gene may be a. found on the Y chromosome b. passed to daughters from their fathers c. passed to sons from their mothers d. expressed more commonly among females e. passed to daughters from their fathers and to sons from their mothers

E

In comparing mitosis and meiosis, which of the following statements is true? a) Meiosis I is more like mitosis than is meiosis II. b) Both processes result in four cells. c) Pairing of homologues occurs in both. d) Chromatids are present only in mitosis. e) Meiosis II resembles mitosis.

E

The F2phenotypic ratio of a monohybrid cross is a. 1:1 b. 2:1. c. 9:3:3:1. d. 1:2:1. e. 3:1

E

Which of the following indicates homozygous genotypes? a. aa b. Aa c. AA d. AA and Aa e. AA and aa

E

10. If tall (D) is dominant to dwarf (d), and two homozygous varieties DD and dd are crossed, then what kind of offspring will be produced? a. all Dd b. all DD c. all dd d. 1/2 DD, 1/2 Dd e. 1/2 Dd, 1/2 dd

a. all Dd

44. In a pedigree chart, a male showing the specific trait being studied is indicated by a a. darkened square b. clear square c. darkened diamond d. clear triangle e. darkened circle

a. darkened square

15. If all the offspring of a testcross are alike and resemble the organism being tested, then that parent is a. homozygous dominant b. homozygous recessive c. heterozygous d. recessive e. incompletely dominant

a. homozygous dominant

18. An individual with a genetic makeup of aa BB is said to be a. pure-breeding b. recessive c. hybrid d. dihybrid e. heterozygous

a. pure-breeding

31. The SRY gene is found on a. the human Y chromosome b. the human X chromosome c. a human autosome d. both the human X and Y chromosomes e. all human chromosomes

a. the human Y chromosome

A testcross consists of a cross

an organism of dominant phenotype but unknown genotype and an organism that is homozygous recessive for that trait

42. Nondisjunction involving the X chromosomes may occur during oogenesis and produce two kinds of eggs. If normal sperm fertilize these two types, which of the following pairs of genotypes are possible? a. XX and XY b. XXY and XO c. XYY and XO d. XYY and YO e. none of these

b. XXY and XO

5. Various forms of a gene at a given locus are called a. chiasmata b. alleles c. autosomes d. loci e. chromatids

b. alleles

28. A bell-shaped curve of phenotypic variation is a representation of a. incomplete dominance b. continuous variation c. multiple alleles d. epistasis e. environmental effects on phenotypes

b. continuous variation

40. Cri-du-chat is caused by a/an a. inversion b. deletion c. duplication d. translocation e. autosomal dominant

b. deletion

46. Which of the following is more common males? a. albinism b. hemophilia c. progeria d. Huntington's disease e. both hemophilia and Huntington's disease

b. hemophilia

32. An X-linked carrier is a a. homozygous dominant female b. heterozygous female c. homozygous recessive female d. homozygous male e. heterozygous male

b. heterozygous female

25. Pleiotropic genes a. act on secondary sexual characteristics b. influence more than one aspect of phenotype c. are additive d. produce lethal effects when homozygous e. none of these

b. influence more than one aspect of phenotype

33. A karyotype a. compares one set of chromosomes to another b. is a visual display of chromosomes arranged according to size c. is a photograph of cells undergoing mitosis during anaphase d. of a normal human cell shows 48 chromosomes e. cannot be used to identify individual chromosomes beyond the fact that two chromosomes are homologues

b. is a visual display of chromosomes arranged according to size

41. The condition occurring when an organism has a 2n + 1 chromosome composition is known as a. monosomy b. trisomy c. diploid d. haploid e. both trisomy and haploid

b. trisomy

19. An individual with a genotype of Aa Bb CC is able to produce how many different kinds of gametes? a. 2 b. 3 c. 4 d. 7 e. 8

c. 4

20. The usual F2 phenotypic ratio of a dihybrid cross is a. 1:1 b. 2:1 c. 9:3:3:1 d. 1:2:1 e. 3:1

c. 9:3:3:1

21. Mendel's dihybrid crosses, but not his monohybrid crosses, showed that a. Some genes were linked together. b. The two alleles controlling a trait were divided equally among the gametes. c. Alleles for different traits were inherited independently. d. One of the pair of alleles is dominant to the other. e. The crossing of two different homozygous forms will not produce any offspring in the first generation that will look like either of the parents.

c. Alleles for different traits were inherited independently.

43. Which of the following is not inherited as an autosomal recessive? a. albinism b. cystic fibrosis c. Marfan's syndrome d. phenylketonuria e. sickle cell disease

c. Marfan's syndrome

1. In Mendel's time, most people believed that a. All genetic traits bred true. b. Only certain forms of domesticated plants and animals bred true. c. The characteristics of parents were blended in the offspring. d. Acquired characteristics were inherited. e. The inheritance of traits was controlled by blood.

c. The characteristics of parents were blended in the offspring.

37. If a daughter expresses an X-linked recessive gene, she inherited the trait from a. her mother b. her father c. both parents d. neither parent e. her grandmother

c. both parents

45. In a pedigree chart, a female who does not demonstrate the trait being studied is represented by a a. darkened square b. clear diamond c. clear circle d. darkened triangle e. darkened oval

c. clear circle

34. Which chemical is used to keep chromosomes from separating during metaphase? a. Giemsa stain b. acetone c. colchicine d. alcohol e. formaldehyde

c. colchicine

14. The results of a testcross reveal that all offspring resemble the parent being tested. That parent necessarily is a. heterozygous b. polygenic c. homozygous d. recessive e. male

c. homozygous

35. Karyotyping involves taking pictures of chromosomes during a. prophase b. telophase c. metaphase d. interphase e. anaphase

c. metaphase

9. According to Mendel, what kind of genes "disappear" in F1 pea plants? a. sex-linked b. dominant c. recessive d. codominant e. lethal

c. recessive

47. Amniocentesis is a. a surgical means of repairing deformities b. a form of chemotherapy that modifies or inhibits gene expression or the function of gene products c. used in prenatal diagnosis to detect chromosomal mutations and metabolic disorders in embryos d. a form of gene replacement therapy e. all of these

c. used in prenatal diagnosis to detect chromosomal mutations and metabolic disorders in embryos

7. Which of the following genotypes show dominant phenotypes? a. aa b. Aa c. AA d. Aa and AA e. AA and aa

d. Aa and AA

17. Mendel's principle of independent assortment states that a. One allele is always dominant to another. b. Hereditary units from the male and female parents are blended in the offspring. c. The two hereditary units that influence a certain trait segregate during gamete formation. d. Each hereditary unit is inherited separately from other hereditary units. e. All of the choices.

d. Each hereditary unit is inherited separately from other hereditary units.

8. Hybrid organisms produced from a cross between two pure-breeding organisms belong to which generation? a. P1 b. H1 c. A1 d. F1 e. F2

d. F1

29. Chromosomes other than those involved in sex determination are known as a. nucleosomes b. heterosomes c. alleles d. autosomes e. liposomes

d. autosomes

16. The theory of segregation a. deals with the alleles governing two different traits b. applies only to linked genes c. applies only to sex-linked genes d. explains the behavior of a pair of alleles during meiosis e. none of these

d. explains the behavior of a pair of alleles during meiosis

22. A gene that produces multiple effects is called a(n) a. multiple allele b. autosome. c. epistatic gene d. pleiotropic gene e. incompletely dominant gene

d. pleiotropic gene

24. Multiple effects of a single gene is known as a. expressivity b. penetrance c. codominance d. pleiotropy e. multiple alleles

d. pleiotropy

48. Phenotypic treatments for genetic disorders include a. preventing the disorders in the carriers b. elimination of the defective gene c. preventing a disorder from being passed on d. preventing a disorder from being expressed e. all of these

d. preventing a disorder from being expressed

3. In his experiments with plants, Mendel removed which part of the plant to prevent unwanted fertilizations? a. flowers b. petals c. pistils d. stamens e. stigmas

d. stamens

4. A locus is a. a recessive gene b. an unmatched allele c. a sex chromosome d. the location of an allele on a chromosome e. a dominant gene

d. the location of an allele on a chromosome

39. A chromosome's gene sequence that was ABCDEFG before modification and ABCDLMNOP afterward is an example of a. inversion b. deletion c. duplication d. translocation e. crossing over

d. translocation

11. The F2 phenotypic ratio of a monohybrid cross is a. 1:1 b. 2:1 c. 9:3:3:1 d. 1:2:1 e. 3:1

e. 3:1

6. Which of the following indicates homozygous genotypes? a. aa b. Aa c. AA d. AA and Aa e. AA and aa

e. AA and aa

26. Genes that are located on the same chromosome a. tend to be inherited together b. usually appear together in the gamete c. are said to be linked d. may be separated during crossing over e. all of these

e. all of these

27. Which of the following may be influenced by the environment? a. ability of plants to grow b. shape of Daphnia heads c. how people handle stress d. fur color in Himalayan rabbits e. all of these

e. all of these

30. Sex chromosomes a. determine sex b. vary from one sex to another c. carry some genes that have nothing to do with sex d. were unknown to Mendel e. all of these

e. all of these

36. Galactosemia a. is an X-linked recessive trait expressed more commonly in males b. occurs more frequently in some ethnic groups than others c. is an autosomal recessive inheritance d. must be homozygous to be expressed e. is an autosomal recessive inheritance and must be homozygous to be expressed

e. is an autosomal recessive inheritance and must be homozygous to be expressed

38. A human X-linked recessive gene may be a. found on the Y chromosome b. passed to daughters from their fathers c. passed to sons from their mothers d. expressed more commonly among females e. passed to daughters from their fathers and to sons from their mothers

e. passed to daughters from their fathers and to sons from their mothers

Males tend to be affected in greater numbers by X-linked recessive genetic disorders than are females because

males have only one X chromosome.

In this generalized illustration of gametogenesis, the four cells in the right column should be labeled

ovum and three polar bodies

A gene locus is

the location of an allele on a chromosome

12. If all offspring of a cross have the genotype Aa, the parents of the crosses would most likely be a. AA x aa b. Aa x Aa c. Aa x aa d. AA x Aa e. none of these

a. AA x aa

2. Which of the following statements is true? a. Darwin did not know which mechanisms were responsible for the variation he saw. b. The blending theory of inheritance provides excellent support for evolution. c. Darwin received Mendel's paper but did not understand its significance. d. The explanation for genetics had no implica tions for evolution. e. All of these.

a. Darwin did not know which mechanisms were responsible for the variation he saw.

23. In incomplete dominance: a. One allele is not dominant to another allele. b. The genotype can be determined by the phenotype. c. The heterozygote is somewhat intermediate to the two homozygotes. d. The intermediate phenotype may be the result of enzyme insufficiency. e. All of these.

a. One allele is not dominant to another allele.