BI 121A--EXAM II NAME______________________________
Fall 1999
I. (12 points) Circle the correct response
1. The replication of DNA occurs ___.
a. between the growth phases of interphase
b. immediately before prophase of mitosis
c. during prophase of mitosis
d. during prophase of meiosis
2. In the cell life cycle of a particular cell, ___.
a. mitosis occurs immediately prior to S
b. mitosis occurs immediately prior to G1
c. G2 procedes S
d. G1 precedes S
e. mitosis and S precede G1
3. In eukaryotic cells, which of the following can occur during mitosis?
a. two mitotic divisions to maintain the parental chromosome number
b. the replication of DNA
c. a long growth period
d. the disappearance of the nuclear envelope and nucleolus
4. Diploid refers to ___.
a. having two chromosomes of each type in somatic cells
b. twice the parental chromosome number
c. half the parental chromosome number
d. having one chromosome of each type in somatic cells
5. If a parent cell has sixteen chromosomes and undergoes mitosis, each resulting cell will have ___ chromosomes.
a. sixty-four
b. thirty-two
c. sixteen
d. eight
e. four
6. The correct order of the stages of mitosis is ___.
a. prophase, metaphase, telophase, anaphase
b. telophase, anaphase, metaphase, prophase
c. telophase, prophase, metaphase, anaphase
d. anaphase, prophase, telophase, metaphase
e. prophase, metaphase, anaphase, telophase
7. During ___, sister chromatids of each chromosome are separated from each other, and those former partners, now chromosomes, are moved toward opposite poles.
a. prophase
b. metaphase
c. anaphase
d. telophase
8. In the process of cytokinesis, cleavage furrows are associated with ___ cell division, and cell plate formation is associated with ___ cell division.
a. animal, animal
b. plant, animal
c. plant, plant
d. animal, plant
II. (9 points) A particular diploid cell has 2 pairs of homologous chromosomes, one long black pair, one short white pair. Diagram the following during meiosis: (a) metaphase I; (b) anaphase I; (c) anaphase II.
a. b. c.
III. (20 points) In garden peas, one pair of alleles controls the height of the plant and a second pair of alleles controls flower color. The allele for tall (D) is dominant to the allele for dwarf (d), and the allele for purple (P) is dominant to the allele for white (p).
(a) A tall plant with purple flowers crossed with a dwarf plant with white flowers produces ½ tall with purple flowers and ½ tall with white flowers. What is the genotype of the parents?
(b) The progeny of a mating are ¼ tall purple, ¼ tall white, ¼ dwarf purple, and ¼ dwarf white. What are genotypes of the parents?
IV. (9 points) An illegitimate child (Dan) is born to Martha Smith. Dan's blood type is O, Martha's is B. Martha points her finger at Bill Jones as the father. Bill is type A and denies the charge. Could he have been the father? Show your figuring. Is this a kind of sex linkage?
V. (20 points) Multiple Choice. Circle the correct response.
1. A colorblind man and a woman with normal vision whose father was colorblind have a son. Colorblindness, in this case, is caused by an X-linked recessive gene. If only the male offspring are considered, the probability that their son is colorblind is
a. .25 (or 25%).
b. .50 (or 50%).
c. .75 (or 75%).
d. 1.00 (or 100%).
e. none of the above
2. Red-green colorblindness is an X-linked recessive trait in humans. A colorblind woman and a man with normal vision have a son. What is the probability that the son is colorblind?
a. 100%
b. 75%
c. 50%
d. 25%
e. 0%
3. Red-green colorblindness is an X-linked recessive trait in humans. What is the probability that a colorblind woman and a man with normal vision will have a colorblind daughter?
a. 100%
b. 75%
c. 50%
d. 25%
e. 0%
4. 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.
5. 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. both b and c
6. An X-linked carrier is a
a. homozygous dominant female.
b. heterozygous female.
c. homozygous recessive female.
d. homozygous male.
e. heterozygous male.
7. Sex chromosomes
a. determine sex.
b. vary from one sex to another.
c. carry some genes that have nothing to do with sex.
d. all of the above
8. A genetic abnormalitiy that may result in sterile males with mental retardation or breast enlargement is
a. XXY.
b. XYY.
c. Turner syndrome.
d. Down syndrome.
e. none of the above
9. Males who tend to be taller than average and show mild mental retardation may be designated
a. XXY.
b. XYY.
c. Turner’s syndrome.
d. Down syndrome.
e. none of the above
10. Nondisjunction involving the X chromosome 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 the above
VI. (10 points) Describe how the enzyme mediating transcription knows where to start and where to stop.
VII. (10 points) What kind of RNA is indicated by the diagram below? What process occurs at site A? at site B?
a. In the lactose operon in bacteria: (a) where does the repressor act? (b) what is its effect? (c) what substance inactivates the repressor?
IX. (4 points) Distinguish between exons and introns.