Chapter 11: Protein synthesis and gene expression

Protein synthesis

The biological process where cells make proteins using instructions from DNA

Transcription

The formation of an mRNA molecule against the template strand of a DNA molecule in the nucleus by complementary nucleotide base pairing

Translation

The joining of amino acids in a specific order to form a polypeptide, according to the mRNA sequence read by ribosomes

Template strand

The DNA strand that serves as a pattern for making complementary polynucleotides

Non-template strand

The DNA strand complementary to the template strand; does not form the pattern for the synthesis of complementary polynucleotides

Promoter region

A non-coding section of DNA upstream of a gene that initiates transcription

RNA polymerase

The enzyme that produces mRNA from the DNA template strand; major enzyme in transcription

Exon

A section of DNA or mRNA that codes for a polypeptide

Intron

A section of DNA or mRNA that does not code for a polypeptide

RNA splicing

The process of removing parts of an mRNA strand, particularly any unnecessary introns, to produce mature mRNA

5' cap

A molecule added to the 5' end of an mRNA strand to protect it from degradation and direct it out of the nucleus

Poly-A tail

A section of repeated adenosine bases added to the end of an mRNA strand to protect it from degradation

Ribosome

The organelle where polypeptide synthesis occurs in all cells

Polypeptide

A polymer of many amino acids linked by peptide bonds; forms a protein or part of a protein

Codon

A series of three adjacent nucleotide bases in DNA and mRNA that codes for a particular amino acid to be added to a polypeptide or signals start or stop

Transfer RNA (tRNA)

A ribonucleic acid molecule with a specific RNA anticodon, paired with a particular amino acid from the cytoplasm, to deliver the amino acid to a growing polypeptide chain inside a ribosome

Anticodon

A sequence of three nucleotide bases on a tRNA molecule that pairs with complementary bases on an mRNA strand during translation at a ribosome

Start codon

The first codon of an mRNA strand translated by a ribosome

Point mutation

A mutation that affects a single base-pair position within a gene

Substitution

When a single nucleotide is swapped for another

Frameshift mutation

A mutation that dislocates the translational reading frame

Reading frame

The ribosome’s division of nucleotides into triplets for translation; shifted by insertion or deletion mutations

Insertion

The addition of a single nucleotide within a sequence

Deletion

The removal of a single nucleotide from a sequence

Gene expression

The process of a gene being transcribed and translated into products, such as proteins or functional RNA

Gene regulation

Various processes that enable a gene to be expressed or not in specific cells at specific times and allow proteins to be produced at required rates

Nucleosome

The basic structural unit of chromatin, comprising a DNA strand wrapped tightly around a group of eight histone proteins

Heterochromatin

A tightly coiled complex of proteins and DNA that is characterised by few genes and limited transcription activity

Housekeeping gene

A gene that encodes a polypeptide essential for basic cellular processes

Transcription factor

A regulatory protein whose function is to activate or inhibit transcription of coding DNA by binding to specific non-coding segments near the gene to be expressed or inhibited

Morphology

The shape and form of an organism or its parts

HOX genes

A gene family that codes for proteins that regulate the body plan in the developing embryo