Unit 4

Gene Expression

Gene function either at the level of traits or at the molecular level

Protein-Coding Gene

A gene that serves as a template make an mRNA molecule that contains the information to specify a polypeptide with a particular amino acid sequence (most genes are protein-coding genes)

Non-Coding RNA (ncRNA)

An RNA molecule that does not code the amino acid sequence of a polypeptide

Mutation

A heritable change in the genetic material

Inborn Error of Metabolism

A genetic defect that produces an inability to metabolize a certain compound

One-Gene/One-Enzyme Hypothesis

An early hypothesis by Beadle and Tatum that suggested that one gene codes one enzyme. It was later modified

Polypeptide

A molecule consisting of a linear sequence of amino acids (the term denotes structure)

Protein

A functional unit composed of one or more polypeptides. Each polypeptide is composed of a linear sequence of amino acids

Transcription

The process that produces an RNA copy of a gene

Messenger RNA (mRNA)

RNA that contains the information to specify a polypeptide with a particular amino acid sequence

Translation

The process of synthesizing a specific polypeptide on a ribosome

Central Dogma

Refers to the steps of gene expression at the molecular level: DNA is transcribed into mRNA, and mRNA is translated into a polypeptide

RNA Modification

The biochemical modification of an RNA

Pre-mRNA

In eukaryotes, the mRNA transcript before any biomedical modifications are made to it

Gene

A unit of heredity. At the molecular level, a this is an organized unit of base sequences in a DNA strand that can be transcribed into RNA and ultimately results in the formation of a functional product

Transfer RNA (tRNA)

An RNA that carries amino acids and is used to translate mRNA into polypeptides

Ribosomal RNA (rRNA)

An RNA that forms part of a ribosomes, which provides the site where translation occurs

Promoter

A sequence of DNA within a gene that controls when and where transcription begins

Terminator

A sequence of DNA within a gene that specifies the end of transcription

Regulatory Sequence

In the regulation of transcription, a DNA sequence that functions as a binding site for a regulatory transcription factor, which is a protein that influences the rate of transcription

Initiation

The first stage in the process of transcription or translation

Sigma Factor

A protein that recognizes the promoter in a bacterial gene and binds RNA polymerase to the promoter

RNA Polymerase

The enzyme that synthesizes strands of RNA during gene transcription

Open Complex

The complex between RNA polymerase and the separated DNA strands

Elongation

The second stage in transcription or translation, in which RNA strands or polypeptides are made, respectively

Template Strand

The DNA strand that is used as a template for RNA synthesis or DNA replication

Coding Strand

The DNA strand opposite to the template strand (or noncoding strand)

Termination

The final stage of transcription, in which the RNA dissociates from the DNA, or of translation, in which the polypeptide is released from the ribosome

Transcription Factor

A protein that influences the ability of RNA polymerase to transcribe genes

Preinitiation Complex

The assembled structure consisting of RNA polymerase II and general transcription factors (GTFs) at the TATA box prior to transcription of eukaryotic protein-coding genes

Pre-mRNA

In eukaryotes, the mRNA transcript before any biochemical modifications are made to it

Mature mRNA

In eukaryotes, transcription produces a longer RNA, called pre-mRNA, which undergoes certain modifications before it exits the nucleus (this is the final functional product)

Capping

The process in which 7-methylguanosine is covalently attached at the 5’ end of pre-mRNAs of eukaryotes

5’ Cap

The 7-methylguanosine structure at the 5’ end of most mature mRNAs in eukaryotes

Poly A Tail

A string of adenine nucleotides at the 3’ end of most mature mRNAs in eukaryotes

Intron

Intervening DNA sequences that are found between coding sequences of genes

Exon

A coding sequence that is found in a mature mRNA molecule after splicing is finished

Splicing

The process in which introns are removed from an RNA molecule, such as a pre-mRNA, and the remaining exons are connected to each other

Spliceosome

A complex of several subunits known as snRNPs that removes introns from eukaryotic pre-mRNAs

Ribozyme

A biological catalyst that is an RNA molecule

Metalloribozyme

A catalytically active RNA that uses one or more metal ions in its catalytic action

Alternative Splicing

The splicing of pre-mRNA in more than one way to allow the production of two or more different polypeptides from the same gene

Self-Splicing

The phenomenon in which an rRNA or a tRNA catalyzes the removal of its own intron(s)