Biology- Gene Expression

NCEA AS91159 Biology 2.5

Peptide bond

The bonds that hold amino acids together in polypeptide chains

Polypeptide chain

A polymer made up of amino acids; it folds to form proteins

Protein

Large molecule made up of one or more polypeptide chains that have a function; it is manufactured in the cytoplasm at the ribosome

Chromosome

A structure in the nucleus made up of DNA which holds the genetic information of an organism

Homologous chromosomes

A pair of chromosomes with the same structure that contain the same genes, but may have different alleles

Template strand

The DNA strand that is used to base-pair complementary nucleotides against to manufacture an RNA strand

Coding strand

The DNA strand that is not used as a template; it has the same base sequence as the mRNA, except it has T instead of U

Transcription

The process by which mRNA is made from DNA in the nucleus

Triplet

3 bases on DNA which code for an amino acid; a triplet is complementary to the codon

Codon

3 bases on mRNA coding for a specific amino acid; complementary to the anticodon portion of tRNA

Anticodon

Part of the tRNA molecule that carries an amino acid to be dropped off while the ribosome continues to read codons

AUG

The start codon on the mRNA

UAA, UAG and UGA

Stop codons which tell the ribosome to stop

Mutation

A sudden change in the base sequence of DNA in an organism

Mutagen

An environmental factor that changes the genetic material, usually DNA, of an organism

mRNA

The copy of a gene in the DNA which leaves the nucleus and is used to make a protein

tRNA

Small RNA molecules that transfer amino acids to a growing polypeptide chain during translation

Ribosome

The site of translation during protein synthesis; it is made up of two subunits containing RNA and protein

Base substitution

The replacement of one base with another within a gene

Base insertion/deletion

The addition or removal of a base within a gene; this causes a reading frameshift and can result in the wrong amino acid sequence or early termination of protein synthesis, producing a non-functional protein

Promotor region

Turns the gene 'on'; RNA polymerase binds to this region to begin transcription of the gene

Terminator region

Signals the end point of transcription

Induced mutations

Caused by exposure to external mutagens

Somatic mutations

Occur in any cells apart from the sex cells; cannot be inherited

Gametic mutations

Occur in the sex cells; can be inherited

Same sense mutations

Cause a change in the DNA sequence but have no effect on the amino acid sequence

Mis sense mutations

Cause a change in the amino acid sequence in the protein; one amino acid can be changed or many

Nonsense mutations

Create a new stop codon in the middle of a gene, which stops translation prematurely and causes a shortened protein

Start codon

AUG; the ribosome begins here and the tRNA comes in and starts translation

Stop codon

A signal for ribosomes to dissociate and translation to finish

Silent mutation

Has no effect on protein function and is often caused by same sense mutations

metabolism

the total sum of all chemical reactions that happen inside the cells of a living organism to sustain life

redundant codons

multiple three-letter nucleotide combinations (codons) code for the same single amino acid