Cell Biology Chapter 20

Question 1

Selective gene expression allows cells to be what? The presence of a gene does not guarantee what?

Answer 1

efficient, synthesizing only what is needed for each cell type; a function, phenotype or trait, etc

Question 2

The expression of a gene is what determines the what? Cells express genes related to their what? House Keeping genes are what?

Answer 2

the properties of a cell; specialized function; genes expressed in all cells

Question 3

Gene expression can be what and into what?

Answer 3

altered; intracellular and extracellular environments

Question 4

Cell differentiation occurs through what? DNA from a differentiated cell when placed in a what can direct what?

Answer 4

changes in expression patterns of genes; an enucleated embryonic cell can direct development of full organisms

Question 5

How can gene expression be regulated? First 3

Answer 5

Controlling when and how often a given gene is transcribed; controlling the splicing and processing of RNA transcripts; Selecting which completed mRNAs are exported from the nucleus to the cytosol and determining where in the cytosol they are localized

Question 6

Gene expression can be regulated how? 2nd 3 points

Answer 6

Selecting which mRNAs in the cytoplasm are translated by ribosomes; Selectively destabilizing certain mRNA molecules in the cytoplasm; Selectively activating, inactivating, degrading, or localizing specific protein molecules after they have been made

Question 7

Bacteria create what? What are operons?

Answer 7

polycistronic mRNAs - mRNAs that encode for more than 1 polypeptide; genes located contiguously on a stretch of DNA and are under the control of one promoter to which the RNA polymerase binds to initiate transcription

Question 8

A single unit of messenger RNA is transcribed from the what and is subsequently translated into what? The regulatory region encodes for what?

Answer 8

from the operon and is subsequently translated into separate proteins; encodes for the regulatory protein

Question 9

The regulatory protein can bind the what and block the what? Regulatory proteins can be bound by molecules to inactivate it and what?

Answer 9

Operator and block the polymerase from transcribing; and keep it from binding to the operator and blocks the polymerase

Question 10

Regulatory proteins can be bound by molecules to activate it and what?

Answer 10

keep it so it binds the operator and blocks the polymerase

Question 11

Gene expression is OFF unless what? What is its name?

Answer 11

unless activated; Inducible operons

Question 12

Gene expression is ON unless what and what is its name?

Answer 12

unless repressed; Repressible operons

Question 13

Regulation of gene expression is accomplished by the combination of what?

Answer 13

general transcription factors, specific transcription factors, regulatory proteins, histone modifying enzymes, chromatin remodeling proteins

Question 14

Regulation of various genes may be regulated by the same what?

Answer 14

protein making the process very effective

Question 15

Transcriptional regulators are what? Some examples of it?

Answer 15

proteins which bind regulatory DNA sequences upstream of the promoter; gene specific transcription factors, can activate or repress gene expression

Question 16

The expression of each gene is regulated by the what?

Answer 16

binding of a particular combination of proteins in the gene’s regulatory region

Question 17

What is a silencer? What are repressors?

Answer 17

a DNA sequence capable of binding transcription regulation factors, called repressors; a DNA or RNA binding protein that inhibits the expression of one or more genes

Question 18

What is an enhancer? What is an activator?

Answer 18

a DNA sequence that can be bound by proteins to increase the transcription of a particular gene; a DNA-binding proteins that bind to enhancers or promoter-promiximal elements to increase gene transcription

Question 19

What are insulators?

Answer 19

sometimes employed to prevent an enhancer or silencer from affecting the wrong gene

Question 20

General transcription factors are essential for what? General transcription factors assemble with what?

Answer 20

transcription o all the genes transcribed by a given type of RNA polymerase; with RNA polymerase at the core promoter very close to the transcription start point

Question 21

Modifying the structure of the chromatin can dramatically affect what? Many transcriptional activators recruit what?

Answer 21

gene expression; Histone Acetyl Transferases which adds acetyl groups resulting in euchromatin

Question 22

Many transcriptional repressor recruit what?

Answer 22

Histone Deacetylases which remove acetyl groups resulting in heterochromatin

Question 23

Histone deacetylation and methylation favor what? Acetylated nonmethylated histones favor what?

Answer 23

compacted, inaccessible chromatin; accessibility of chromatin to the transcriptional machinery

Question 24

DNA methylation can cause what? Methylation of promoter regions can do what?

Answer 24

transcriptional repression; block access of proteins needed for transcription

Question 25

Differentiated cells are distinguished from each other based on what? Such differences indicate that differential gene expression plays a central role in what?

Answer 25

difference in appearance and protein products; central role in creating differentiated cells

Question 26

As cells differentiate, they acquire unique sets of what? The combination of these tissue specific regulators is ultimately what controls what?

Answer 26

regulatory proteins specific to that cell type; differential gene expression between differentiated cell types

Question 27

Alterations in tissue specific regulatory proteins can change differentiated cells into what? Multiple control elements and transcription factors act in combination to establish what? Different cell types possess what?

Answer 27

into other cell types; patterns of gene expression in different cell types; different sets of transcription factors

Question 28

Differentiated cells give rise to what? First two steps of how that happens

Answer 28

cells of the same cell type; a transient signal induces differentiation of the parent cells; that signal induces expression of regulator proteins

Question 29

Last two steps of giving rise to cells of the same cell type

Answer 29

The regulator protein enhances expression of its own expression in addition to tissue-specific gene expression; this ensure that the regulator protein will continue to be expressed in daughter cells without the initial signal

Question 30

Epigenetic changes are what?

Answer 30

stable alterations in gene expression transmitted from one generation to the next without any change in DNA sequence

Question 31

DNA methylation changes:

Answer 31

Methylation of cytosine nucleotides of DNA recruit proteins that generally inhibit translation; Methylation patters are copied to newly synthesized strands during DNA replication by maintenance methyltransferase

Question 32

Histone code changes:

Answer 32

modification of histones through acetylation and deacetylation; half parental histones are inherited on new strand following replicaiton, carrying parental histone code; code copied to new histones nearby; reestablishes chromatin structure new daughter cells

Question 33

Post-transcriptional regulation code:

Answer 33

Alternative splicing; mRNA export and localization; stability of mRNA; longer poly(A) tail = longer half life; ncRNA regulation (non-coding RNA); siRNA (RNAi), miRNA

Question 34

RNAi (RNA interference) is based on the ability o small RNAs to do what? Double stranded RNA knocks down what?

Answer 34

trigger mRNA degradation; the expression of specific genes

Question 35

A cytoplasmic ribonuclease called what cleaves what? The resulting fragments are called what?

Answer 35

Dicer cleaves the double stranded RNA into short fragments about 21-22 bp long; siRNAs (small interfering or silencing RNAs)

Question 36

The siRNAs combine with a group of proteins to form a what?

Answer 36

an inhibitor of gene expression called RISC (RNA-induces silencing complex), in this case called the siRISC

Question 37

One of the strands is what and the remaining one binds the what? If pairing between what and the what is a what mRNA is what?

Answer 37

degraded, binds the siRISC to a target mRNA by complementary base pairing; siRNA and mRNA is a close match, mRNA is degraded

Question 38

MicroRNAs (miRNAs) are produced by what? These bind to and regulate expression of what?

Answer 38

genes found in almost all eukaryotes; genes that are separate from the genes that produce the miRNAs

Question 39

miRNAs are initially transcribed into what? Looped pri-miRNAs are converted into what?

Answer 39

longer molecules called primary microRNAs which fold into hairpin loops; mature miRNAs

Question 40

A nuclear enzyme called what cleaves the what into smaller what? The pre-miRNAs are exported to where?

Answer 40

Drosha cleaves the pri-mRNAs are into smaller hairpins called precursor miRNAs; to the cytoplasm wher DIcer cleaves them to form a miRNA

Question 41

The miRNA forms a what? mRNAs with fully complementary sequences are what? mRNAs with partially complementary sequences are what?

Answer 41

miRISC, which inhibits expression of mRNAs containing sequences complementary to the miRNA; degraded by miRISC; translationally inhibited

Question 42

Xist RNA is a what? It is transcribed from X chromosomes that become inactive and then what?

Answer 42

long noncoding RNA involved in X chromosome inactivation; once a chromosome begins to transcribe Xist RNA, it eventually becomes largely inactive

Question 43

Xist RNA spreads to what? This leads to recruitment of what?

Answer 43

coat the inactive chromosome; chromatin-modifying proteins that promote condensation

Question 44

Post translational control: Protein stability; Protein activity

Answer 44

Ubiquitination and targeted degradation; Modificatons induce conformational changes that affect protein function

Question 45

Summary of Eukaryotic Gene regulation

Answer 45

genomic control, transcription control, RNA processing and nuclear export, translational control, posttranslational control