Chapter 18 New

Question 1

operator

Answer 1

In bacterial and phage DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon.

Question 2

operon

Answer 2

A unit of genetic function found in bacteria and phages, consisting of a promoter, and operator, and a coordinately regulated cluster of genes whose products function in a common pathway.

Question 3

repressor

Answer 3

A protein that inhibits gene transcription. In prokaryotes, repressors bind to the DNA in or near the promoter. In eukaryotes, repressors may bind to control elements within enhancers, to activators, or to other proteins in a way that blocks activators from binding to DNA.

Question 4

regulatory gene

Answer 4

A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.

Question 5

corepressor

Answer 5

A small molecule that binds to a bacterial repressor protein and changes the protein’s shape, allowing it to bind to the operator and switch an operon off.

Question 6

inducer

Answer 6

A specific small molecule that binds to a bacterial repressor protein and changes the repressor’s shape so that it cannot bind to an operator, thus switching an operon on.

Question 7

cyclic AMP (cAMP)

Answer 7

Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is common intracellular signaling molecule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons.

Question 8

activator

Answer 8

A protein that binds to DNA and stimulates gene transcription. In prokaryotes, activators bind in or near the promoter; in eukaryotes, activators generally bind to control elements in enhancers.

Question 9

differential gene expression

Answer 9

The expression of different sets of genes by cells with the same genome.

Question 10

histone acetylation

Answer 10

The attachment of acetyl groups to certain amino acids of histone proteins.

Question 11

DNA methylation

Answer 11

The presence of methyl groups on the DNA bases (usually cytosine) of plants animals, and fungi. (The term also refers to the process of adding methyl groups to DNA bases.)

Question 12

epigenetic inheritance

Answer 12

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence of a genome.

Question 13

control element

Answer 13

A segment of noncoding DNA that helps regulate transcription of a gene by serving as a binding site for a transcription factor. Multiple control elements are present in a eukaryotic gene’s enhancer.

Question 14

enhancer

Answer 14

A segment of eukaryotic DNA containing multiple control elements, usually located far from the gene whose transcription it regulates.

Question 15

alternative RNA splicing

Answer 15

A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.

Question 16

proteasome

Answer 16

A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.

Question 17

microRNA (miRNA)

Answer 17

A small, single-stranded RNA molecule, generated from a hairpin structure on a precursor RNA transcribed from a particular gene. The miRNA associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence.

Question 18

RNA interference (RNAi)

Answer 18

A technique used to silence the expression of selected genes. RNAi uses synthetic double-stranded RNA molecules that match the sequence of a particular gene to trigger the breakdown of the gene’s messenger RNA.

Question 19

small interfering RNA (siRNA)

Answer 19

One of multiple small, single-stranded RNA molecules generated by cellular machinery from a long, linear, double-stranded RNA molecule. The siRNA associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence. In some cases, siRNA can also block transcription by promoting chromatin modification.

Question 20

differentiation

Answer 20

The process by which a cell or group of cells become specialized in structure and function.

Question 21

morphogenesis

Answer 21

The development of the form of an organism and its structures.

Question 22

cytoplasmic determinants

Answer 22

A maternal substance, such as a protein or RNA, that when placed into an egg influences the course of early development by regulating the expression of genes that affect the developmental fate of cells.

Question 23

induction

Answer 23

The process in which one group of embryonic cells influences the development of another, usually by causing changes in gene expression.

Question 24

determination

Answer 24

The progressive restriction of developmental potential in which the possible fate of each cell becomes more limited as an embryo develops. At the end of determination, a cell is committed to its fate.

Question 25

pattern formation

Answer 25

The development of a multicellular organism’s spatial organization, the arrangement of organs and tissues in their characteristic places in three-dimensional space.

Question 26

positional information

Answer 26

Molecular cues that control pattern formation in an animal or plant embryonic structure by indicating a cell’s location relative to the organism’s body axes. These cues elicit a response by genes that regulate development.

Question 27

homeotic genes

Answer 27

Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the development fate of groups of cells.

Question 28

embryonic lethal

Answer 28

A mutation with a phenotype leading to death of an embryo or larvae.

Question 29

maternal effect gene

Answer 29

A gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the offspring’s genotype. Maternal effect genes, also called egg-polarity genes, were first identified in <em>Drosophila melanogaster</em>.

Question 30

egg-polarity gene

Answer 30

A gene that helps control the orientation (polarity) of the egg; also called a maternal effect gene.

Question 31

<em>bicoid</em>

Answer 31

A maternal effect gene that codes for a protein responsible for specifying the anterior end in <em>Drosophila melanogaster</em>.

Question 32

morphogen

Answer 32

A substance, such as Bicoid protein in <em>Drosophila</em>, that provides positional information in the form of a concentration gradient along an embryonic axis.

Question 33

oncogene

Answer 33

A gene found in viral or cellular genomes that is involved in triggering molecular events that can lead to cancer.

Question 34

proto-oncogene

Answer 34

A normal cellular gene that has the potential to become an oncogene.

Question 35

tumor-suppressor gene

Answer 35

A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.

Question 36

<em>ras</em> gene

Answer 36

A gene that codes for Ras, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle.

Question 37

<em>p53</em> gene

Answer 37

A tumor-suppressor gene that codes for a specific transcription factor that promotes the synthesis of proteins that inhibit the cell cycle.