Chapter 18/19

Question 1

activator

Answer 1

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 2

alternative RNA splicing

Answer 2

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 3

bicoid

Answer 3

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

Question 4

control element

Answer 4

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 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

cyclic AMP (cAMP)

Answer 6

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

Question 7

cytoplasmic determinant

Answer 7

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 8

determination

Answer 8

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 9

differential gene expression

Answer 9

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

Question 10

differentiation

Answer 10

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

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

embryonic lethal

Answer 12

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

Question 13

enhancer

Answer 13

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

Question 14

epigenetic inheritance

Answer 14

Inheritance of traits transmitted by mechanisms that do not involve the nucleotide sequence.

Question 15

histone acetylation

Answer 15

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

Question 16

homeotic gene

Answer 16

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

Question 17

inducer

Answer 17

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 18

induction

Answer 18

A process in which a group of cells or tissues influences the development of another group through close-range interactions.

Question 19

long noncoding RNA (lncRNA)

Answer 19

An RNA between 200 and hundreds of thousands of nucleotides in length that does not code for protein but is expressed at significant levels.

Question 20

maternal effect gene

Answer 20

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 Drosophila melanogaster.

Question 21

microRNA (miRNA)

Answer 21

A small, single-stranded RNA molecule, generated from a double-stranded RNA precursor. 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 22

morphogen

Answer 22

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

Question 23

morphogenesis

Answer 23

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

Question 24

oncogene

Answer 24

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

Question 25

operator

Answer 25

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 26

operon

Answer 26

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

Question 27

p53 gene

Answer 27

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

Question 28

pattern formation

Answer 28

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

Question 29

positional information

Answer 29

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 30

proto-oncogene

Answer 30

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

Question 31

ras gene

Answer 31

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 32

regulatory gene

Answer 32

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

Question 33

repressor

Answer 33

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 34

RNA interference (RNAi)

Answer 34

A mechanism for silencing the expression of specific genes. In RNAi, double-stranded RNA molecules that match the sequence of a particular gene are processed into siRNAs that either block translation or trigger the degradation of the gene’s messenger RNA. This happens naturally in some cells, and can be carried out in laboratory experiments as well.

Question 35

small interfering RNA (siRNA)

Answer 35

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.

Question 36

tumor-suppressor gene

Answer 36

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