Chapter 18 Questions

Question 1

Why is it important for bacterial cells to be able to only produce the products only when needed?

Answer 1

In order to conserve energy

-A cell can regulate the production of enzymes by feedback inhibition or by gene regulation

Question 2

What are the two major targets of bacterial negative feedback inhibition of genes?

Answer 2

Regulation of enzyme
 activity and Regulation of enzyme
production

Question 3

How many promotors are used in an operon?

Answer 3

2 possible ones

Question 4

Are the genes in an operon transcribed all at once or one at a time?

Answer 4

all at once

Question 5

What enzyme is responsible for transcribing the genes that are found in an operon?

Answer 5

RNA polymerase

Question 6

What would happen if one of the genes in an operon was shut off?

Answer 6

The enzymes will not be produced

Question 7

What would happen in one the enzymes in a metabolic pathway was inhibited?

Answer 7

Final product not produced

Question 8

What is the difference between repressible operons and inducible operons?

Answer 8

repressible - can be turned off by a repressor when gene products are abundant
inducible - transcription can be turned on by an inducer when gene products are needed

Question 9

Is the tryptophan operon (trp operon) a repressible or inducible operon?

Answer 9

repressible

Question 10

Is the lactose operon (lac operon) a repressible or inducible operon?

Answer 10

inducible

Question 11

Are corepressors used in repressible operons or inducible operons?

Answer 11

repressible

Question 12

What is the corepressor for the trp operon? Does the lac operon use a corepressor?

Answer 12

tryptophan and protein.

no

Question 13

What is the inducer for the lac operon? Does the trp operon use an inducer?

Answer 13

allolactose and protein

no

Question 14

Does the trp operon use a repressor? Does the lac operon use a repressor?

Answer 14

yes

no

Question 15

What are the two ways that eukaryotic cells regulate gene expression?

Answer 15

Regulation of Chromatin Structure and Regulation of Transcription Initiation

Question 16

What are the two ways that chromatin structure can be regulated?

Answer 16

Histone Modification and

DNA Methylation

Question 17

Although all somatic cells in the human body are genetically identical, we can produce several types of specialized cells (example brain cells, heart cells, liver cells, skin cells white blood cells, etc.) What allows for this development of cells into the various cell types?

Answer 17

Differential gene expression is how multicellular organisms produce specialized cells that are very different from each other

Question 18

What chromatin proteins can be altered to regulate gene expression?

Answer 18

histones

Question 19

Which form of chromatin is tightly packed and relatively inactive?

Answer 19

histone methylation

Question 20

Which form of chromatin is more loosely packed and is relatively active?

Answer 20

histone acetylation

Question 21

What are two ways that histones can be altered to regulated gene expression?

Answer 21

histone acetylation and histone methylation

Question 22

Which organic functional group can be added to histones to tighten chromatin and repress gene expression?

Answer 22

methyl groups

Question 23

Which organic functional group can be attached to histones to loosen chromatin to promote gene expression?

Answer 23

acetyl groups

Question 24

What effect does methylation of DNA typically have?

Answer 24

can cause long-term inactivation of genes in cellular differentiation
-In genomic imprinting, methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development

Question 25

Eukaryotic cells require transcription factors that bind to control elements in the promotor region of a gene. What role does transcription factors play in transcription?

Answer 25

To initiate transcription, eukaryotic RNA polymerase requires the assistance of transcription factors

Question 26

What is the difference between specific and general transcription factors?

Answer 26

• General transcription factors are essential for the transcription of all protein-coding genes
• Specific transcription factors are used to increase or decrease the amount of transcription that occurs for a specific gene

Question 27

What effect would a lack of transcription factors have on gene expression?

Answer 27

no transcription would occur