Biology 12 SAC 1

Reliability

Reliability

Consistency of measurement

Validity

the extent to which a test measures or predicts what it is supposed to

Accuracy

how close a measurement is to the true value

Precision

a measure of how close a series of measurements are to one another

Reproducibility

Independent researchers arriving at the same results using their own data and methods

Tryptophan

An amino acid that is used to synthesize proteins

Amino acid

Molecules used by all living things to make proteins

Operon

A cluster of genes that are transcribed together to give a single mRNA molecule, which therefore encodes multiple proteins

Repressor

A protein that inhibits (prevents) the expression of one or more genes

Co-repressor

Proteins that regulate the process of gene expression indirectly by binding to the repressor protein

Attenuation

(Limiting the job of something)

A second mechanism to control tryptophan produced. It doesn’t stop transcription but it limits translation. In this process the RNA polymerase transcribes leader region, ribosome translates mRNA to the stop codon, section 3+4 bind the moving attenuator away from RNA polymerase, then the RNA polymerase is dislodged from the DNA and doesn’t transcribe the operon

Promotor region

A region of DNA upstream of a gene where relevant proteins (such as RNA polymerase) bind to initiate transcription of that particular gene.

Operator region

A region of DNA that overlaps with or lies just downstream of the RNA polymerase binding site (promotor region). Region found in between the promotor and the genes of the operon

leader region

This region comes after the operator region, and can control the expression of the operon through the process of attenuation. This region has four sections (1-4).

Attenuator

This is a nucleotide sequence in DNA that can lead to premature termination of transcription. After section four is the attenuator, this is because its presence is required to reduce (attenuate) mRNA transcription in the presence of high levels of trp.