Chapter 18.2 and 18.3

Question 1

Prokaryotes and eukaryotes alter gene expression in response to

Answer 1

their changing environment

Question 2

In multicellular eukaryotes,

Answer 2

gene expression regulates the development and is responsible for differences in cell types
Ex. Muscle cell v. nerve cell

Question 3

RNA molecules play many roles in

Answer 3

regulating gene expression in eukaryotes

Question 4

Eukaryotic gene expression is regulated at

Answer 4

many stages

Question 5

All organisms must regulate which genes are

Answer 5

expressed at any given time

Question 6

In multicellular organisms regulation of gene expression is

Answer 6

essential for cell specialization

Question 7

Almost all the cells in an organism are

Answer 7

genetically identical

Question 8

Differences between cell types result from

Answer 8

differential gene expression, the expression of different genes by cells with the same genome

Question 9

Abnormalities in gene expression can lead to

Answer 9

diseases including cancer

Question 10

Gene expression is regulated at

Answer 10

many stages

Question 11

Genes with highly packed heterochromatin are

Answer 11

usually not expressed

Question 12

Chemical modifications to histones and DNA of chromatin

Answer 12

influence both chromatin structure and gene expression

Question 13

In histone acetylation,

Answer 13

acetyl groups are attached to positively charged lysines in histone tails.

This loosens chromatin structure, thereby promoting the initiation of transcription

Question 14

The addition of methyl groups (methylation) can condense chromatin; the addition of phosphate groups (phosphorylation)

Answer 14

next to a methylated amino acid can loosen chromatin

Question 15

The histone code hypothesis proposes that

Answer 15

specific combinations of modifications, as well as the order in why they occur, help determine chromatin configuration and influence transcription

Question 16

DNA methylation, the addition of methyl groups to certain bases in DNA, is

Answer 16

associated with reduced transcription in some species

Question 17

DNA methylation can

Answer 17

cause long-term inactivation of genes in cellular differentiation

Question 18

In genomic imprinting,

Answer 18

methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development

Question 19

Although the chromatin modifications just discussed do not alter DNA sequence,

Answer 19

they may be passed to future generations of cells

Question 20

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called

Answer 20

epigenetic inheritance

Question 21

Chromatin-modifying enzymes provide

Answer 21

initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery

Question 22

Associated with most eukaryotic genes are multiple control elements,

Answer 22

segments of noncoding DNA that serve as binding sites for transcription factors that help regulate transcription

Question 23

Control elements and the transcription factors they bind are critical to

Answer 23

the precise regulation of gene expression in different cell types

Question 24

To initiate transcription,

Answer 24

eukaryotic RNA polymerase requires the assistance of proteins called transcription factors

Question 25

General transcription factors are

Answer 25

essential for the transcription of all protein-coding genes

Question 26

In eukaryotes, high levels of transcription of particular genes depend on

Answer 26

control elements interacting with specific transcription factors

Question 27

Proximal control elements are located close to

Answer 27

the promoter

Question 28

Distal control elements, groupings of which are called enhances, may be

Answer 28

far away from a gene or even located in an intron

Question 29

An activator is a

Answer 29

protein that binds to an enhancer and stimulates transcription of a gene

Question 30

Activators have two domains,

Answer 30

one that binds DNA and a second that activates transcription

Question 31

Bound activators facilitate a

Answer 31

sequence of protein-protein interactions that result in transcription of a given gene

Question 32

Some transcription factors function as

Answer 32

repressors, inhibiting expression of a particular gene by a variety of methods

Question 33

Some activators and repressors act indirectly by

Answer 33

influencing chromatin structure to promote or silence transcription

Question 34

Transcription alone dow not account for

Answer 34

gene expression

Question 35

Regulatory mechanisms can

Answer 35

operate at various stages after transcription

Question 36

Such mechanisms allow a cell to

Answer 36

fine-tune gene expression rapidly in response to environmental changes

Question 37

In alternative RNA splicing,

Answer 37

different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns

Question 38

The life span of mRNA molecules in the cytoplasm is a

Answer 38

key to determining protein synthesis

Question 39

Eukaryotic mRNA is more long lived than

Answer 39

prokaryotic mRNA

Question 40

Nucleotide sequences that influence the lifespan of mRNA eukaryotes reside in the

Answer 40

untranslated region (UTR) at the 3' end of the molecule

Question 41

The initiation of translation of selected mRNAs can be

Answer 41

blocked by regulatory proteins that bind to sequences or structures of the mRNA

Question 42

Alternatively, translation of all mRNAs in a cell may be

Answer 42

regulated simultaneously

Question 43

For example, translation initiation factors are

Answer 43

simultaneously activated in an egg following fertilization

Question 44

After translation,

Answer 44

various types of protein processing, including cleavage and the addition of chemical groups, are subject to control

Question 45

Proteasomes are

Answer 45

giant protein complexes that bind protein molecules and degrade them

Question 46

Noncoding RNAs play

Answer 46

multiple roles in controlling gene expression

Question 47

Only a small fraction of DNA codes for proteins, and

Answer 47

a very small fraction of the non-protein-coding DNA consists of genes for RNA such as rRNA and tRNA

Question 48

A significant amount of the genome may be

Answer 48

transcribed into noncoding RNAs (ncRNAs)

Question 49

Noncoding RNAs regulate gene expression at two points:

Answer 49

mRNA translation and chromatin configuration

Question 50

MicroRNAs (miRNAs) are

Answer 50

small single-stranded RNA molecules that can bind to mRNA. These can degrade mRNA or block its translation

Question 51

The phenomenon of inhibition of gene expression by RNA molecules is called

Answer 51

RNA interference (RNAi)

Question 52

RNAi is caused by

Answer 52

small interfering RNAs (siRNAs)

Question 53

siRNAs and miRNAs are similar but

Answer 53

form from different RNA precursors

Question 54

In some yeasts siRNAs play a role in

Answer 54

heterochromatin formation and can block large regions of the chromosome

Question 55

Small ncRNAs called piwi-associated RNAs (piRNAs) induce

Answer 55

heterochromatin, blocking the expression of parasitic DNA elements in the genome, known as transposons

Question 56

RNA-based mechanisms may also block

Answer 56

transcription of single genes

Question 57

Small ncRNAs can regulate

Answer 57

gene expression at multiple steps

Question 58

An increase in the number of miRNAs in a species may have allowed

Answer 58

morphological complexity to increase over evolutionary time

Question 59

siRNAs may have evolved first, followed by

Answer 59

miRNAs and later piRNAs