Mastering Biology Chapter Nineteen

Expression of different sets of genes in cells with the same genome. Responsible for creating different cell types

The complex of DNA and proteins, mainly histones, that compose eukaryotic chromosomes. Can be highly compact (heterochromatin) or loosely coiled (euchromatin)

The process by which the DNA in chromatin is unwound from its associated proteins to allow transcription or replication. May involve chemical modification of histone proteins or reshaping of the chromatin by large multiprotein complexes in an ATP-requiring process.

In eukaryotes, the changes that a primary RNA transcript undergoes to become a mature RNA molecule. For pre-RNA it includes the addition of a 5' cap and poly(A) tail and splicing to remove introns.

One of several positively charged (basic) proteins associated with DNA in the chromatin of eukaryotic cells.

A repeating, bead-like unit of eukaryotic chromatin, consisting of about 200 nucleotides of DNA wrapped twice around eight histone proteins.

A class of eukaryotic enzymes that add a methyl group to cytosines in DNA. Methylation of DNA leads to chromatin condensation and is an important means of regulating gene expression in eukaryotes

The addition of a methyl group to a DNA molecule

The hypothesis that specific combinations of chemical modifications of histone proteins contain information that influences chromatin condensation and gene expression.

A class of eukaryotic enzymes that loosen chromatin structure by adding acetyl groups to histone proteins.

A class of eukaryotic enzymes that condense chromatin by removing acetyl groups from histone proteins.

Addition of an acetyl group to a molecule. Acetylation of histone proteins is important in controlling chromatin condensation.

Set of enzymes that use energy from ATP hydrolysis shift nucleosomes on DNA to expose regulatory sequences to transcription factors

A short nucleotide sequence in DNA that binds a sigma factor (in bacteria) or basal transcription factors (in eukaryotes) to enable RNA polymerase to begin transcription. In bacteria, several contiguous genes are often transcribed from a single promoter. In eukaryotes, each gene generally has its own promoter.

A short DNA sequence in many eukaryotic promoters about 30 base pairs upstream from the transcription start site.

A protein that binds to the TATA box in eukaryotic promoters and is a component of the basil transcription start site

Any segment of DNA that is involved in controlling transcription of a specific gene by binding a regulatory transcription factor protein

In eukaryotes, regulatory sequences in DNA that are close to a promoter and that an bind regulatory transcription factors

A regulatory sequence in eukaryotic DNA that may be located far from the gene it controls or within introns of the gene. Binding of specific proteins to an enhancer enhances the transcription of certain genes

Regulation of gene expression by various mechanisms that change the rate at which genes are transcribed to form messenger RNA. In negative control, binding of a regulatory protein to DNA represses transcription; in positive control, binding of regulatory protein to DNA promotes transcription.

A regulatory sequence in eukaryotic DNA to which repressor proteins can bind, inhibiting gene transcription

(1) In bacteria, a protein that binds to an operator sequence in DNA to prevent transcription when an inducer is not present and that comes off DNA to allow transcription when an inducer binds to the repressor protein. (2) In eukaryotes, a protein that binds to a silencer sequence in DNA to prevent or reduce gene transcription

Proteins, present in all eukaryotic cells, that bind to promoters and help initiate transcription

regulatory proteins in eukaryotes that form a physical link between regulatory transcription factors that are bound to DNA, the basal transcription complex, and RNA polymerase.

In eukaryotes, the splicing of primary RNA transcripts from a single gene in different ways to produce different mature mRNAs and thus different polypeptides

Degration of an RNA molecule or inhibition of its translation following its binding by a short RNA (microRNA) whose sequence is complementary to a portion of the mRNA

A small, single-stranded RNA associated with proteins in an RNA-induced silencing complex (RISC). Processed from a longer premiRNA gene transcript. Can bind to complementary sequences in mRNA molecules, allowing the associated proteins of RISC to degrade the bound mRNA or inhibit its translation

A macromolecular machine that destroys proteins that have been marked by the addition of ubiquitin.

A protein that prevents cell division, such as when the cell has DNA damage. Mutant genes that code for tumor suppressors are associated with cancer

Any gene that encourages cell division in a regulated manner, typically by triggering specific phases in the cell cycle. Mutation may convert it into an oncogene.

Any gene whose protein product stimulates cell division at all times and thus promotes cancer development. Often is a mutated form of a gene involved in regulating the cell cycle.

A tumor-suppressor protein that responds to DNA damage by stopping the cell cycle, turning on DNA repair machinery, and, if necessary, triggering apoptosis.

The complex of DNA and proteins found in eukaryotes

A gene or protein that holds cell division in check unless conditions are right for the cell to divide.

They are found in a variety of locations and are functional in any orientation.

The set of regulatory transcription factors present in a particular cell, not differences in in DNA sequence, are largely responsible for which genes are expressed.

mRNA processing events that lead to different combinations of exons being spliced together

Regulatory transcription factors as activators

(a) Enhancers and the araC site are similar because both are sites in DNA where regulatory proteins bind. They are different because enhancers generally are located at great distances from the promoter. (b) Promoter-proximal elements and the lac operon operator are both regulatory sites in DNA located close to the promoter. (c) Basal transcription factors and sigma are proteins that must bind to the promoter before RNA polymerase can initiate transcription. They differ because sigma is part of the RNA polymerase holoenzyme, while the basal transcription complex recruits RNA polymerase to the promoter.

If changes in the environment cause changes in how spliceosomes function, then the RNAs and proteins produced from a particular gene could change in a way that helps the cell cope with the new environmental conditions.

(a) Enhancers and silencers are both regulatory sequences located at a distance from the promoter. Enhancers bind regulatory transcription factors that activate transcription; silencers bind regulatory factors that shut down transcription. (b) Promoter-proximal elements and enhancers are both regulatory sequences that bind positive regulatory transcription factors. Promoter-proximal elements are located close to the promoter; enhancers are far from the promoter. (c) Transcription factors bind to regulatory sites in DNA; mediator does not bind to DNA but instead forms a bridge between regulatory transcription factors and basal transcription factors.

Inhibition of a histone deacetylase is predicted to leave acetyl groups on histones longer than normal. This is predicted to keep gene transcription going longer than normal, leading to higher levels of particular proteins and a change in the phenotype of the cell.

Does not depend on particular base sequences. this is because there are many more modifications in the histone code relative to the genetic code.

The cell is predicted to arrest in the cell cycle and most likely will commit suicide through activation of apoptosis genes because of the continually active p53.

show a lower frequency of promoter-enhancer association

The double-stranded RNA could be cut by the same enzyme that creates double-stranded miRNAs from miRNA precursors. This double-stranded RNA may be incorporated into RISC and converted into a single-stranded RNA. The single-stranded RNA held by RISC would work in RNA interference