Question 1

Which of the following is characteristic of the product of the p53 gene?

Accepted Answer

A) It is an activator for other genes. 
B) It speeds up the cell cycle. 
C) It causes cell death via apoptosis. 
D) It allows cells to pass on mutations due to DNA damage. 
E) It slows down the rate of DNA replication by interfering with the binding of DNA polymerase.

Question 2

Which of the following can contribute to the development of cancer?

Accepted Answer

A) random spontaneous mutations 
B) mutations caused by X-rays 
C) transposition 
D) chromosome translocations 
E) all of the above

Question 3

A lack of this nonprotein molecule would result in the inability of the cell to "turn off" genes:

Accepted Answer

A) operon 
B) inducer 
C) promoter 
D) repressor 
E) corepressor

Question 4

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in

Accepted Answer

A) continuous transcription of the structural gene controlled by that regulator. 
B) complete inhibition of transcription of the structural gene controlled by that regulator. 
C) irreversible binding of the repressor to the operator. 
D) inactivation of RNA polymerase by alteration of its active site. 
E) continuous translation of the mRNA because of alteration of its structure.

Question 5

In response to chemical signals, prokaryotes can do which of the following?

Accepted Answer

A) turn off translation of their mRNA 
B) alter the level of production of various enzymes 
C) increase the number and responsiveness of their ribosomes 
D) inactivate their mRNA molecules 
E) alter the sequence of amino acids in certain proteins

Question 6

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then the

Accepted Answer

A) amino acid inactivates the repressor. 
B) enzymes produced are called inducible enzymes. 
C) repressor is active in the absence of the amino acid. 
D) amino acid acts as a corepressor. 
E) amino acid turns on transcription of the operon.

Question 7

When this is taken up by the cell, it binds to the repressor so that the repressor no longer binds to the operator:

Accepted Answer

A) operon 
B) inducer 
C) promoter 
D) repressor 
E) corepressor

Question 8

These genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo:

Accepted Answer

A) homeotic genes 
B) segmentation genes 
C) egg-polarity genes 
D) morphogens 
E) inducers

Question 9

In a series of experiments, the enzyme Dicer has been inactivated in cells from various vertebrates, and the centromere is abnormally formed from chromatin. Which of the following is most likely to occur?

Accepted Answer

A) The usual mRNAs transcribed from centromeric DNA will be missing from the cells. 
B) Tetrads will no longer be able to form during meiosis I. 
C) Centromeres will be euchromatic rather than heterochromatic and the cells will soon die in culture. 
D) The cells will no longer be able to resist bacterial contamination. 
E) The DNA of the centromeres will no longer be able to replicate.

Question 10

The tryptophan operon is a repressible operon that is

Accepted Answer

A) permanently turned on. 
B) turned on only when tryptophan is present in the growth medium. 
C) turned off only when glucose is present in the growth medium. 
D) turned on only when glucose is present in the growth medium. 
E) turned off whenever tryptophan is added to the growth medium.

Question 11

The fact that plants can be cloned from somatic cells demonstrates that

Accepted Answer

A) differentiated cells retain all the genes of the zygote. 
B) genes are lost during differentiation. 
C) the differentiated state is normally very unstable. 
D) differentiated cells contain masked mRNA. 
E) differentiation does not occur in plants.

Question 12

Mutations in these genes lead to transformations in the identity of entire body parts:

Accepted Answer

A) homeotic genes 
B) segmentation genes 
C) egg-polarity genes 
D) morphogens 
E) inducers

Question 13

Use the following scenario for the following questions.
A few decades ago, Knudsen and colleagues proposed a theory that, for a normal cell to become a cancer cell, a minimum of two genetic changes had to occur in that cell. Knudsen was studying retinoblastoma, a childhood cancer of the eye.
-In colorectal cancer, several genes must be mutated in order to make a cell a cancer cell, supporting Knudsen's hypothesis. Which of the following kinds of genes would you expect to be mutated?

Accepted Answer

A) genes coding for enzymes that act in the colon 
B) genes involved in control of the cell cycle 
C) genes that are especially susceptible to mutation 
D) the same genes that Knudsen identified as associated with retinoblastoma 
E) the genes of the bacteria that are abundant in the colon

Question 14

Which of the following describes the function of an enzyme known as Dicer?

Accepted Answer

A) It degrades single-stranded DNA. 
B) It degrades single-stranded mRNA. 
C) It degrades mRNA with no poly(
A) tail. 
D) It trims small double-stranded RNAs into molecules that can block translation. 
E) It chops up single-stranded DNAs from infecting viruses.

Question 15

For a repressible operon to be transcribed, which of the following must occur?

Accepted Answer

A) A corepressor must be present. 
B) RNA polymerase and the active repressor must be present. 
C) RNA polymerase must bind to the promoter, and the repressor must be inactive. 
D) RNA polymerase cannot be present, and the repressor must be inactive. 
E) RNA polymerase must not occupy the promoter, and the repressor must be inactive.

Question 16

Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell?

Accepted Answer

A) enzymatic shortening of the poly(
A) tail 
B) removal of the 5' cap 
C) methylation of C nucleotides 
D) memethylation of histones 
E) removal of one or more exons

Question 17

One of the hopes for use of recent knowledge gained about non-coding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs?

Accepted Answer

A) exploring a way to turn on the expression of pseudogenes 
B) targeting siRNAs to disable the expression of an allele associated with autosomal recessive disease 
C) targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease 
D) creating knock-out organisms that can be useful for pharmaceutical drug design 
E) looking for a way to prevent viral DNA from causing infection in humans

Question 18

Use the following scenario for the following questions.
A few decades ago, Knudsen and colleagues proposed a theory that, for a normal cell to become a cancer cell, a minimum of two genetic changes had to occur in that cell. Knudsen was studying retinoblastoma, a childhood cancer of the eye.
-One of the human leukemias, called CML (chronic myelogenous leukemia)is associated with a chromosomal translocation between chromosomes 9 and 22 in somatic cells of bone marrow. Which of the following allows CML to provide further evidence of this multi-step nature of cancer?

Accepted Answer

A) CML usually occurs in more elderly persons (late age of onset). 
B) The resulting chromosome 22 is abnormally short; it is then known as the Philadelphia chromosome. 
C) The translocation requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces. 
D) CML involves a proto-oncogene known as abl. 
E) CML can usually be treated by chemotherapy.

Question 19

What do gap genes, pair-rule genes, segment polarity genes, and homeotic genes all have in common?

Accepted Answer

A) Their products act as transcription factors. 
B) They have no counterparts in animals other than Drosophila. 
C) Their products are all synthesized prior to fertilization. 
D) They act independently of other positional information. 
E) They apparently can be activated and inactivated at any time of the fly's life.

Question 20

Which of the following is established prior to fertilization in Drosophila eggs?

Accepted Answer

A) the anterior-posterior and dorsal-ventral axes 
B) the position of the future segments 
C) the position of the future wings, legs, and antennae 
D) A and B only 
E) A, B, and C

Exam 18: Control of Gene Expression