Cell Biology Chapter 20 Flashcards
Selective gene expression allows cells to be what? The presence of a gene does not guarantee what?
efficient, synthesizing only what is needed for each cell type; a function, phenotype or trait, etc
The expression of a gene is what determines the what? Cells express genes related to their what? House Keeping genes are what?
the properties of a cell; specialized function; genes expressed in all cells
Gene expression can be what and into what?
altered; intracellular and extracellular environments
Cell differentiation occurs through what? DNA from a differentiated cell when placed in a what can direct what?
changes in expression patterns of genes; an enucleated embryonic cell can direct development of full organisms
How can gene expression be regulated? First 3
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
Gene expression can be regulated how? 2nd 3 points
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
Bacteria create what? What are operons?
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
A single unit of messenger RNA is transcribed from the what and is subsequently translated into what? The regulatory region encodes for what?
from the operon and is subsequently translated into separate proteins; encodes for the regulatory protein
The regulatory protein can bind the what and block the what? Regulatory proteins can be bound by molecules to inactivate it and what?
Operator and block the polymerase from transcribing; and keep it from binding to the operator and blocks the polymerase
Regulatory proteins can be bound by molecules to activate it and what?
keep it so it binds the operator and blocks the polymerase
Gene expression is OFF unless what? What is its name?
unless activated; Inducible operons
Gene expression is ON unless what and what is its name?
unless repressed; Repressible operons
Regulation of gene expression is accomplished by the combination of what?
general transcription factors, specific transcription factors, regulatory proteins, histone modifying enzymes, chromatin remodeling proteins
Regulation of various genes may be regulated by the same what?
protein making the process very effective
Transcriptional regulators are what? Some examples of it?
proteins which bind regulatory DNA sequences upstream of the promoter; gene specific transcription factors, can activate or repress gene expression
The expression of each gene is regulated by the what?
binding of a particular combination of proteins in the gene’s regulatory region
What is a silencer? What are repressors?
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
What is an enhancer? What is an activator?
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
What are insulators?
sometimes employed to prevent an enhancer or silencer from affecting the wrong gene
General transcription factors are essential for what? General transcription factors assemble with what?
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
Modifying the structure of the chromatin can dramatically affect what? Many transcriptional activators recruit what?
gene expression; Histone Acetyl Transferases which adds acetyl groups resulting in euchromatin
Many transcriptional repressor recruit what?
Histone Deacetylases which remove acetyl groups resulting in heterochromatin
Histone deacetylation and methylation favor what? Acetylated nonmethylated histones favor what?
compacted, inaccessible chromatin; accessibility of chromatin to the transcriptional machinery
DNA methylation can cause what? Methylation of promoter regions can do what?
transcriptional repression; block access of proteins needed for transcription
Differentiated cells are distinguished from each other based on what? Such differences indicate that differential gene expression plays a central role in what?
difference in appearance and protein products; central role in creating differentiated cells
As cells differentiate, they acquire unique sets of what? The combination of these tissue specific regulators is ultimately what controls what?
regulatory proteins specific to that cell type; differential gene expression between differentiated cell types
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?
into other cell types; patterns of gene expression in different cell types; different sets of transcription factors
Differentiated cells give rise to what? First two steps of how that happens
cells of the same cell type; a transient signal induces differentiation of the parent cells; that signal induces expression of regulator proteins
Last two steps of giving rise to cells of the same cell type
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
Epigenetic changes are what?
stable alterations in gene expression transmitted from one generation to the next without any change in DNA sequence
DNA methylation changes:
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
Histone code changes:
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
Post-transcriptional regulation code:
Alternative splicing; mRNA export and localization; stability of mRNA; longer poly(A) tail = longer half life; ncRNA regulation (non-coding RNA); siRNA (RNAi), miRNA
RNAi (RNA interference) is based on the ability o small RNAs to do what? Double stranded RNA knocks down what?
trigger mRNA degradation; the expression of specific genes
A cytoplasmic ribonuclease called what cleaves what? The resulting fragments are called what?
Dicer cleaves the double stranded RNA into short fragments about 21-22 bp long; siRNAs (small interfering or silencing RNAs)
The siRNAs combine with a group of proteins to form a what?
an inhibitor of gene expression called RISC (RNA-induces silencing complex), in this case called the siRISC
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?
degraded, binds the siRISC to a target mRNA by complementary base pairing; siRNA and mRNA is a close match, mRNA is degraded
MicroRNAs (miRNAs) are produced by what? These bind to and regulate expression of what?
genes found in almost all eukaryotes; genes that are separate from the genes that produce the miRNAs
miRNAs are initially transcribed into what? Looped pri-miRNAs are converted into what?
longer molecules called primary microRNAs which fold into hairpin loops; mature miRNAs
A nuclear enzyme called what cleaves the what into smaller what? The pre-miRNAs are exported to where?
Drosha cleaves the pri-mRNAs are into smaller hairpins called precursor miRNAs; to the cytoplasm wher DIcer cleaves them to form a miRNA
The miRNA forms a what? mRNAs with fully complementary sequences are what? mRNAs with partially complementary sequences are what?
miRISC, which inhibits expression of mRNAs containing sequences complementary to the miRNA; degraded by miRISC; translationally inhibited
Xist RNA is a what? It is transcribed from X chromosomes that become inactive and then what?
long noncoding RNA involved in X chromosome inactivation; once a chromosome begins to transcribe Xist RNA, it eventually becomes largely inactive
Xist RNA spreads to what? This leads to recruitment of what?
coat the inactive chromosome; chromatin-modifying proteins that promote condensation
Post translational control: Protein stability; Protein activity
Ubiquitination and targeted degradation; Modificatons induce conformational changes that affect protein function
Summary of Eukaryotic Gene regulation
genomic control, transcription control, RNA processing and nuclear export, translational control, posttranslational control
