Chapter 19

Question 1

A gene that must be expressed continually for the cell to survive.

Answer 1

housekeeping gene

Question 2

The continual expression of a gene.

Answer 2

constitutive gene expression:

Question 3

The conditional expression of a gene based on the cellular need for the gene product, achieved by the presence or absence of activators, repressors, enhancers, and other regulatory factors.

Answer 3

regulated gene expression

Question 4

The positive regulation of the expression of a gene or genes.

Answer 4

activation

Question 5

A decrease in the expression of a gene in response to a change in the activity of a regulatory protein.

Answer 5

repression

Question 6

In eukaryotes, a protein that affects the regulation and transcription initiation of a gene by binding to a regulatory sequence near or within the gene and interacting with RNA polymerase and/or other transcription factors.

Answer 6

transcription factor

Question 7

(1) A DNA-binding protein that positively regulates the expression of one or more genes; that is, transcription rates increase when an activator is bound to the DNA.

(2) A positive modulator of an allosteric enzyme.

Answer 7

activator

Question 8

A protein that binds to the regulatory sequence or operator for a gene, blocking its transcription.

Answer 8

repressor

Question 9

A DNA sequence involved in regulating the expression of a gene; for example, a promoter or operator. Also called a regulatory site.

Answer 9

regulatory sequence

Question 10

The increased expression of a gene by the binding of an activator protein.

Answer 10

positive regulation

Question 11

The decreased expression of a gene due to the binding of a repressor protein.

Answer 11

negative regulation

Question 12

The characteristic of an enzyme or other protein in which binding of the first molecule of a ligand changes the affinity for the second molecule. In positive cooperativity, the affinity for the second ligand molecule increases; in negative cooperativity, it decreases.

Answer 12

cooperativity

Question 13

The interaction of proteins bound at distant sites on a DNA molecule so that the intervening DNA forms a loop.

Answer 13

DNA looping

Question 14

A DNA sequence that facilitates the expression of a given gene; it may be located a few hundred, or even thousand, base pairs away from the gene. In yeast, enhancers are called upstream activator sequences (UASs).

Answer 14

enhancer

Question 15

A protein that stimulates transcription by binding both the RNA polymerase and an activator or activators, without binding the DNA directly.

Answer 15

coactivator

Question 16

A protein that inhibits transcription by binding both the RNA polymerase and a repressor or repressors, without binding the DNA directly.

Answer 16

corepressor

Question 17

A short sequence of DNA that prevents inappropriate cross-signaling between regulatory elements for different genes. Also called a boundary element.

Answer 17

insulator

Question 18

The control of gene expression by the net effect of multiple, sometimes conflicting, regulatory signals.

Answer 18

signal integration

Question 19

A region of DNA that interacts with a repressor protein to control the expression of a group of genes organized in an operon.

Answer 19

operator

Question 20

A small molecule that binds a transcription activator or repressor, causing a conformational change in the regulatory protein that results in an increase or decrease in transcription from the gene.

Answer 20

effector

Question 21

A contiguous mRNA with more than two genes that can be translated into proteins.

Answer 21

polycistronic mRNA:

Question 22

A unit of genetic expression consisting of one or more cotranscribed genes and the operator and promoter sequences that regulate their transcription.

Answer 22

operon

Question 23

A group of genes or operons that are coordinately regulated even though some, or all, may be spatially distant in the chromosome or genome.

Answer 23

regulon

Question 24

The use of specific combinations of a limited number of regulatory proteins to exert fine control over gene expression.

Answer 24

combinatorial control

Question 25

The α helix in a DNA regulatory protein that recognizes and binds to the DNA regulatory site.

Answer 25

recognition helix

Question 26

A sequence that is the reversed complement of a downstream sequence.

Answer 26

inverted repeat

Question 27

A supersecondary protein motif consisting of two α helices separated by a β turn. This motif is crucial to the interaction of many bacterial regulatory proteins with DNA.

Answer 27

helix-turn-helix motif:

Question 28

A conserved 60 amino acid sequence motif in transcription activators encoded by genes that regulate body pattern development.

Answer 28

homeodomain motif

Question 29

A leucine zipper motif in which one side of the recognition helix has a series of basic residues, which facilitates DNA binding.

Answer 29

basic leucine zipper motif:

Question 30

A protein structural motif involved in DNA recognition by some DNA-binding proteins; characterized by a single atom of zinc coordinated to four Cys residues or to two His and two Cys residues.

Answer 30

zinc finger motif:

Question 31

A class of small RNA molecules (21 to 23 nucleotides after processing is complete) involved in gene silencing by inhibiting translation and/or promoting the degradation of particular mRNAs.

Answer 31

microRNA (miRNA):

Question 32

Methods of gene silencing, mediated by short interfering RNAs (siRNAs) or microRNAs (miRNAs), which bind to and silence the mRNA transcript, usually by targeting it for degradation. MicroRNAs are endogenous to the cell, produced by nucleases from longer transcripts encoded in the genome; siRNAs are generated by the same cellular enzymes from exogenous double-stranded RNA, introduced into the cell by viral infection or experimental manipulation.

Answer 32

RNA interference (RNAi):

Question 33

A large assembly of enzymatic complexes that function in the degradation of damaged or unneeded cellular proteins. In eukaryotes, also called a 26S proteasome.

Answer 33

proteasome