(4) Chapter 18

Question 1

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

Answer 1

the amino acid acts as a corepressor.

Question 2

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

Answer 2

RNA polymerase must bind to the promoter, and the repressor must be inactive.

Question 3

Which of the following results is most likely to occur if acetylation of histone tails in the chromatin of embryonic cells is increased?

Answer 3

decreased chromatin condensation

Question 4

If the DNA of a mammalian promoter region experiences increased methylation on cytosine (C) which of the following results is most likely to occur?

Answer 4

inactivation of the gene

Question 5

It is possible for a cell to make proteins that last for months, hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?

Answer 5

short-lived proteins enable the cells to control their activities precisely and efficiently

Question 6

Muscle cells differ from nerve cells mainly because they

Answer 6

express different genes.

Question 7

The functioning of enhancers is an example of

Answer 7

transcriptional control of gene expression.

Question 8

Within a cell, the amount of protein made using a given mRNA molecule depends partly on

Answer 8

the rate at which the mRNA is degraded.

Question 9

Which of the following is the most likely phenotypes of a yeast mutant that contains histones that are resistant to acetylation?

Answer 9

The mutant will show decreased levels of gene expression.

Question 10

Which of the following statements correctly describes the primary difference between enhancers and proximal control elements?

Answer 10

Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter.

Question 11

Tests (assays) analyzing transcriptional control of gene expression focus on which of the following characteristics?

Answer 11

amount of the mRNA generated

Question 12

How are genes coordinately controlled in eukaryotic cells?

Answer 12

Coordinately controlled genes in eukaryotic cells share a set of control elements and are activated by the same chemical signals.

Question 13

A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____.

Answer 13

two-headed fly

Question 14

The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.

Answer 14

the establishment of the anterior-posterior axis

Question 15

The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the _____.

Answer 15

head

Question 16

What triggers the translation of bicoid mRNA?

Answer 16

fertilization of the egg

Question 17

The bicoid gene is a type of _____ gene.

Answer 17

egg-polarity

Question 18

What process produces the gradient of bicoid protein in a fertilized egg?

Answer 18

diffusion

Question 19

Bicoid mRNA is translated in _____.

Answer 19

the fertilized egg

Question 20

The bicoid gene is transcribed by _____.

Answer 20

nurse cells

Question 21

In wildtype Drosophila embryos, the bicoid mRNA is localized to the anterior end of the embryo. If bicoid mRNA was injected into the embryo’s posterior end as well, which of the following developmental events would occur?

Answer 21

The embryo would show anterior structures at both ends of the embryo.

Question 22

Which of the following is true of the cytoplasm of an unfertilized egg?

Answer 22

It is an unevenly distributed (gradients) mixture of mRNA, proteins, organelles, and other substances. Many proteins are found concentrated at one end of the cell or another and provide positional information to the developing embryo.

Question 23

How do cells become differentiated?

Answer 23

different genes are expressed so that different proteins are produced. (Cell differentiation results from changes in gene expression)

Question 24

Cytoplasmic determinants are best described as having which of the following characteristics?

Answer 24

They are maternal substances in the egg that influence the course of early development.

Question 25

Which of the following describes the normal function of the p53 gene product?

Answer 25

It inhibits the cell cycle.

Question 26

Two main types of genes involved in cancer development are

Answer 26

proto-oncogenes and tumor-suppressor genes

Question 27

Which of the following would be most likely to lead to cancer?

Answer 27

amplification of a proto-oncogene and inactivation of a tumor-suppressor gene

Question 28

All your cells contain proto-oncogenes, which can change into cancer-causing genes. Why do cells possess such potential time bombs?

Answer 28

proto-oncogenes are necessary for the normal control of cell growth and division

Question 29

Which of the following statements correctly describes a characteristic of tumor-suppressor genes?

Answer 29

They encode proteins that help prevent uncontrolled cell growth.