Chapter 18 Terms

Question 1

operon

Answer 1

the entire stretch of DNA that includes the operator, the promoter, and the genes that they control

Question 2

operator

Answer 2

The “switch” is a segment of DNA called an operator usually positioned within the promoter

Question 3

repressible operon

Answer 3

transcription of the operon is on by default, but can be turned off by a repressor molecule when gene products are abundant

Question 4

repressor

Answer 4

molecule that can turn off transcription of the operon in repressible operons when gene products are abundant

Question 5

inducible operon

Answer 5

transcription of the operon is off by default, but can be turned on by an inducer molecule when the gene products are needed

Question 6

inducer

Answer 6

molecule that can turn on transcription of operon in inducible operon when products are needed

Question 7

corepressor

Answer 7

a small molecule that binds to the repressor to activate the repressor of an operon

Question 8

differential gene expression

Answer 8

Differential gene expression is how multicellular organisms produce specialized cells that are very different from each other (example: heart cells, liver cells, brain cells, skins cells, white blood cells, etc.)

Question 9

histones

Answer 9

Chemical modifications to histones and DNA of chromatin influence both chromatin structure and gene expression

Question 10

histone acetylation

Answer 10

acetyl groups are attached to histone which loosens chromatin structure, thereby promoting the initiation of transcription

Question 11

histone methylation

Answer 11

methyl groups are attached to histones which tightens chromatin structure, thereby promoting the repression of transcription

Question 12

DNA methylation

Answer 12

the addition of methyl groups to certain bases in DNA, which is associated with reduced transcription in some species

Question 13

control elements

Answer 13

Associated with most eukaryotic genes are multiple control elements, segments of noncoding DNA that serve as binding sites for transcription factors that help regulate transcription

Question 14

transcription factors

-general and specific

Answer 14

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

• 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