Gene Expression (AS91159) - Key terms for the NCEA Exam

Amino acid

The building blocks of proteins. Joined together by peptide bonds to form a polypeptide chain.

Anticodon

Three consecutive bases on a tRNA molecule. Complementary to a codon.

Base-pairing rule

The pairing of A with T (U in RNA) and C with G in nucleic acids that ensures accurate transcription and translation in protein synthesis.

Coding Strand

The strand of DNA that is identical to the mRNA strand (except that DNA has T instead of U).

Codon

Three consecutive bases / nucleotides on an mRNA strand.

Degeneracy

Many amino acids are coded for by more than one amino acid meaning some mutations (e.g. some substitution mutations) do not change the amino acid sequence.

Enzyme

A biological catalyst / protein that speeds up a chemical reaction.

Frameshift Mutation

An insertion or deletion of nucleotides that is not a multiple of three. Every triplet (and therefore codon and resulting amino acid) from the mutation onwards is likely to change.

Gene

A section of DNA that codes for a specific characteristic / trait.

Insertion mutation

A mutation where a base (or bases) are added to the DNA sequence.

Deletion mutation

A mutation where a base (or bases) are removed from the DNA sequence.

Metabolic pathway

A series of enzyme-controlled reactions where the product of one reaction becomes the substrate for the next reaction.

mRNA

Messenger RNA. Single strand of RNA that is complementary to the DNA template strand. Forms in the nucleus (during transcription) and moves to the ribosome where translation occurs.

Mutation

Permanent change in the DNA sequence of an organism.

Environmental factor

A factor such as diet, humidity, temperature etc that can affect gene expression.

Mutagen

An environmental factor that changes the DNA sequence / causes a mutation to occur.

Phenotype

The physical expression of the genotype.

Genotype

The particular alleles an individual possesses.

Point Mutation

A mutation where one base is substituted, deleted or inserted in a DNA sequence.

Polypeptide Chain

Sequence of many amino acids joined together with peptide bonds.

Substrate

A molecule / substance that is acted on by an enzyme in a metabolic pathway to form a product.

Protein Synthesis

The process of creating a protein / polypeptide chain from the DNA. It includes two key steps; transcription and translation.

Ribosome

The organelle in the cytoplasm that is the site of translation.

Silent mutation

A mutation that does not change the amino acid sequence (also called a same-sense mutation).

Substitution mutation

A mutation where a nucleotide is changed to another nucleotide.

Template Strand

The strand of DNA used to make a complementary copy in the form of mRNA during transcription.

Transcription

The process of forming an mRNA strand, complementary to the DNA template strand. Occurs in the nucleus.

Translation

The formation of a polypeptide chain from an mRNA strand. Occurs at a ribosome.

Triplet

Three consecutive bases / nucleotides in the DNA.

tRNA

Transfer RNA. Each tRNA carries a specific amino acid to the ribosome during translation in the formation of a polypeptide chain.