Kapitel 7 Flashcards
Production of different RNAs from the same gene by splicing the transcript in different ways. (Figure 7–57)
alternative RNA splicing
Retention by cells and their descendants of altered patterns of gene expression without any change in DNA sequence.
cell memory
Region of DNA in vertebrate genomes with a greater than average density of CG sequences; these regions generally remain unmethylated.
CG island
DNA sequences to which transcription regulators bind to control the rate of gene transcription. In nearly all cases - these sequences must be on the same chromosome (that is - in cis) to the genes they control. (Figure 7–18)
cis-regulatory sequences
A defense mechanism in bacteria using small noncoding RNA molecules (crRNAs) to seek out and destroy invading viral genomes through complementary base-pairing and targeted nuclease digestion.
CRISPR
Small noncoding RNAs (≈30 nucleotides) that are the effectors of CRISPR-mediated immunity in bacteria.
crRNAs
Addition of methyl groups to DNA. Extensive methylation of the cytosine base in CG sequences is used in plants and animals to help keep genes in an inactive state.
DNA methylation
The set of linked DNA sequences regulating expression of a particular gene. Includes promoter and cis-regulatory sequences required to initiate transcription of the gene and control the rate of transcription. (Figure 7–17)
gene control region
Phenomenon in which a gene is either expressed or not expressed in the offspring depending on which parent it is inherited from. (Figure 7–49)
genomic imprinting
Differentiated cells that are induced by artificial expression of a specific set of transcription regulators to resemble pluripotent embryonic stem cells that are derived directly from embryos.
induced pluripotent stem cells (iPS cells)
Specific site in a eukaryotic mRNA - other than at the 5′ end - at which translation can be initiated. (Figure 7–68)
internal ribosome entry site (IRES)
One of a large group (≈8000 in humans) of RNAs longer than 200 nucleotides and not coding for protein. The functions - if any - of most lncRNAs is unknown but individual lncRNA are known to play important roles in the cell - for example - in telomerase function and genomic imprinting. In a general sense - lncRNAs are believed to act as scaffolds - holding together proteins and nucleic acids to speed up a wide variety of reactions in the cell.
long noncoding RNA (lncRNA)
A transcription regulator specifically required for formation of a particular cell type. Artificial expression of master transcription regulators (alone or in combination with others) will often convert one cell type into another.
master transcription regulator
Short (21–26 nucleotide) eukaryotic RNAs - produced by the processing of specialized RNA transcripts coded in the genome - that regulate gene expression through complementary base-pairing with mRNA. Depending on the extent of base-pairing - miRNA can lead either to rapid destruction of the mRNA or to a block in its translation. (Figure 7–75)
microRNAs (miRNAs)
Expression of only one of the two copies of a gene in a diploid genome - occurring - for example - as a result of imprinting or X-chromosome inactivation.
monoallelic gene expression
Regulation by a cell of gene expression by selectively preserving or destroying certain mRNA molecules in the cytoplasm.
mRNA degradation control
A class of small noncoding RNAs made in the germ line that - in complex with Piwi proteins - keep in check the movement of transposable elements by transcriptionally silencing transposon genes and destroying RNAs produced by them.
piRNAs (piwi-interacting RNAs)
Any control on gene expression that is exerted at a stage after transcription has begun. (Figure 7–54)
post-transcriptional controls
The selective activation - inactivation - degradation - or compartmentalization of specific proteins after they have been made. One of the means by which a cell controls which proteins are active at a given time or location in the cell.
protein activity control
Mechanisms controlling export of mRNAs from the nucleus to the cytosol that can be used to regulate gene expression. Also includes the selective import of proteins and RNA molecules into the nucleus.
regulated nuclear transport
Type of RNA processing that alters the nucleotide sequence of an RNA transcript after it is synthesized by inserting - deleting - or altering individual nucleotides.
RNA editing
As originally described - mechanism by which an experimentally introduced double-stranded RNA induces sequence-specific destruction of complementary mRNAs. The term RNAi is often used to include the inhibition of gene expression by microRNAs (miRNAs) and piwi RNAs (piRNAs) - which are encoded in the cell’s own genome.
RNA interference (RNAi)
Regulation by a cell of gene expression by controlling the processing of RNA transcripts - which includes their splicing.
RNA processing control
Regulation by a cell of gene expression by selecting which completed mRNAs are exported from the nucleus to the cytosol and determining where in the cytosol they are localized.
RNA transport and localization control
Short (21–26 nucleotide) double-stranded RNAs that inhibit gene expression by directing destruction of complementary mRNAs. Production of siRNAs is usually triggered by exogenously introduced double-stranded RNA. (Figure 7–77)
small interfering RNAs (siRNAs)
General name for any protein that binds to a specific DNA sequence (known as a cis-regulatory sequence) to influence the transcription of a gene.
transcription regulators
Regulation by a cell of gene expression by controlling when and how often a given gene is transcribed.
transcriptional control
Regulation by a cell of gene expression by selecting which mRNAs in the cytoplasm are translated by ribosomes.
translational control
Inactivation of one copy of the X chromosome in the somatic cells of female mammals.
X-inactivation
Site in an X chromosome at which inactivation is initiated and spreads outward.
X-inactivation center (XIC)
