Ch 6 The Control Of Gene Expression Flashcards
Coding RNA
An RNA transcript of a protein-coding gene.
Non-coding RNA (ncRNA)
A functional RNA molecule that is not translated into a protein (i.e. the product of a non-coding gene) for example ribosomal RNA (rRNA) or transfer RNA (tRNA).
Ribosomal RNA (rRNA)
The RNA that, together with proteins, makes up the structures called ribosomes, which are the sites of synthesis of proteins by the process of translation.
Transfer RNA (tRNA)
Small RNA molecules involved in protein synthesis at the ribosome. Each tRNA molecule carries an amino acid and a particular anticodon (a triplet of bases), which binds to a complementary codon in mRNA, adding the appropriate amino acid to the growing polypeptide chain.
Primary RNA transcript
A eukaryotic RNA transcript immediately after transcription in the nucleus, before any processing e.g. RNA splicing or polyadenylation.
Posttranscriptional modification
The enzymatic processing of the eukaryotic primary RNA transcript to produce a mature transcript; production of a mature mRNA requires capping, polyadenylation and intron splicing.
RNA splicing
A post-transcriptional process that removes the non-coding sequences (introns) from the transcribed mRNA to produce the mature mRNA molecule.
Post-translational modifications
The enzymatic processing of polypeptides after translation to produce the mature functional protein. For example, proteins that are intended for export, or for incorporation into membranes, pass into the lumen of the ER, where they undergo post-translational modification including glycosylation; the addition of short sugar chains to form a glycoprotein. Other types of modification include the addition of other chemical groups (such as phosphates or lipids) or cleavage.
Capping
The process of adding a modified guanosine nucleotide (GTP residue) to the 5’-end (the beginning) of a eukaryotic mRNA molecule.
Polyadenylation
The post-transcriptional addition of a series of adenosine nucleotides to the 3’ end of a eukaryotic mRNA.
Initiation
Transcription can be divided into three stages. Initiation is the first stage in which the RNA polymerase binds to the DNA template. Translation also has an initiation stage in which a ribosome assembles at the appropriate place on a messenger RNA.
Elongation
Transcription can be divided into three stages. Elongation is the second stage (after initiation), in which the RNA polymerase moves along ‘reading’ the DNA template and synthesising RNA. Translation also has an elongation stage.
Termination
Transcription can be divided into three stages. Termination is the third stage in which mRNA synthesis (elongation) ceases and the transcript dissociates from the template. Translation also has a termination stage.
Core promoter
A region of DNA present in all prokaryotic genes which includes the binding site for RNA polymerase and the site where transcription is initiated.
Consensus sequences
The most common sequence of bases (or amino acids) in a region of sequence homology found in many different genes (or proteins) in different species. Conserved sequences often indicate a conserved function.
Transcription initiation complex
A complex assembly of proteins, including transcription factors and RNA polymerase, that binds to DNA at a specific site upstream of a gene called a promoter, where it initiates transcription of the gene sequence into RNA.
Transcription start site
The site in a gene promoter sequence at which the DNA starts to be copied into RNA sequence during transcription.
Regulatory DNA elements
Short consensus sequences in DNA that are specifically recognised and bound by DNA binding proteins called transcription factors. These factors either promote the recruitment of RNA polymerase to the promoter, thereby increasing transcription of the gene (transcriptional activators), or repress recruitment of the RNA polymerase and decrease transcription of the gene (transcriptional repressors).
Transcription factors
Proteins that bind to specific DNA sequences, promoting (activators) or inhibiting (repressors) the recruitment of RNA polymerase to specific gene promoters, thereby controlling the transcription of genes.
DNA binding motifs
Common structural features on different DNA-binding proteins (includng transcription factors) which facilitate their binding to DNA. Three typical DNA binding motifs are the helix–turn–helix motif, the zinc finger, and the leucine zipper.
Catabolite activator protein (CAP)
The gene regulatory protein that binds cAMP and is involved in the transcriptional regulation of some bacterial operons.
Lac operon
lac operon - Group of adjacent and coordinately controlled genes concerned with the metabolism of lactose in E. coli.
Negative inducible regulation
A type of gene expression control in bacteria. Transcription of a gene under this type of control is induced only when a repressor protein present in the cell is inactivated.
Positive inducible regulation
A type of gene expression control in bacteria. Transcription of a gene under this type of control is induced only when an specific activator molecule becomes activated.
Attenuation
Describing a mechanism of downregulating gene expression in bacteria, in which the transcription of an mRNA molecule is prematurely terminated due to a structural modification; in other words, the RNA molecule transcribed is incomplete.
Transcription terminator
A sequence in RNA being transcribed from a DNA template that, when encountered by the RNA polymerase enzyme, signals the termination of RNA synthesis.
Growth factors
A general term for signalling molecules, usually polypeptides, that bind to cells carrying appropriate receptors and ultimately alter gene expression to stimulate growth, survival or division of the cell.
Hormones
Signalling molecules that in animals are produced by specialised epithelial cells and transported to their target cells elsewhere in the body via the blood circulation. They affect the growth, behaviour or metabolism of cells with appropriate receptors. Plants also have hormones, referred to as phytohormones. Hormones may be peptides, steroids or other types of molecules.
General transcription factors
Proteins that bind to the core promoter and assemble the transcription initiation complex; essential for RNA polymerase binding and the initiation of gene transcription.
Specific transcription factors
Molecules that bind to regulatory DNA elements and have an effect on gene expression.
Housekeeping genes
Genes that are constitutively expressed (at a relatively constant level) in most cells types in an organism; they code for molecules involved in the basic functions necessary for maintenance of the cell.
Enhancers
Regulatory DNA elements which may be located some distance from the gene and, when bound by transcriptional activator proteins, stimulate gene expression. Common in eukaryotes but rare in prokaryotes.
Silencers
Regulatory sequences in DNA that, when bound by transcriptional repressor proteins, reduce the rate of transcription of a gene or genes; typically located some distance away from the gene(s). Common in eukaryotes but rare in prokaryotes
Northern blotting
A technique used to separate and identify specific cellular mRNA molecules; involving gel electrophoresis and transfer to a synthetic membrane, followed by hybridisation to a labelled probe.
Capping
The process of adding a modified guanosine nucleotide to the 5’-end (the beginning) of a eukaryotic mRNA molecule.
Reqd for export through pores nucleus
Ribosome binding and mRNA translation
Prevents enzymes in cytoplasm from degrading mRNA from five prime end before it can be translated
Poly(A) tail
The series of adenosine nucleotides added to the 3’ end of eukaryotic mRNA after transcription.
MicroRNAs (miRNAs)
Small, non-coding, regulatory RNA molecules, about 22 nucleotides long, found in eukaryotic cells and which can silence the expression of certain genes.
Ribosome binding site
A short consensus sequence on mRNA where the ribosome binds during the initiation of translation.
Polysomes
The name for the structure formed by a group of ribosomes and partially translated polypeptides attached to a single molecule of mRNA during the process of translation.
Combinatorial control
The way a group of transcription factors work together to determine level of expression of a single gene.
siRNA
Small interfering RNAs -approximately 22 base pairs long.
