Biology: Transcription and Translation

What is transcription?

the process of making RNA from DNA

Where does transcription occur?

nucleus

What happens in initiation (transcription)?

RNA polymerase binds to sigma factor which causes it to bind to the promoter and the DNA is unwound

What happens in elongation (transcription)?

RNA polymerase slides along the DNA and synthesizes RNA

What happens in termination (transcription)?

termination signal is reached RNA polymerase and mRNA transcript are released

What happens in RNA processing?

introns are spliced out and exons are linked together, poly A tail is added to 3' end and a cap is added to 5' end

What is the function of poly A tail?

increases mRNA stability and lifespan

What is the function of capping?

needed for mRNA to leave nucleus and bind to ribosomes

What are the three types of RNA?

mRNA, tRNA, rRNA

What is translation?

the decoding of an mRNA message into a protein

Where does translation occur?

ribosomes

What is genetic code?

sequences of bases in an mRNA molecule, read in groups of three known as codons

What is the start codon?

AUG

What are four important properties of genetic code?

redundant, conservative, unambiguous, and non-overlapping

What is gene expression?

DNA to a functional protein

What is an anticodon?

the tRNA complement to the mRNA codon

What does tRNA carry?

amino acids and anti codons

What does aminoacyl-tRNA synthetase do?

attaches amino acid to tRNA

What are the three sites in a ribosome?

A site, P site, E site

What does the A site do?

holds the tRNA carrying the next amino acid to be added to the chain (attachment site)

What does the P site do?

holds the tRNA carrying the growing polypeptide chain

What does the E site do?

tRNA exits (exit site)

What is a point mutation?

change in one base

What is the mutation when there is no change in amino acid?

silent (neutral)

What is the mutation when one amino acid changes?

missense (neutral, beneficial, or degenerative)

What is the mutation where the polypeptide shortens?

nonsense (degenerative)

What is the mutation where it produces a different amino acid sequence?

frameshift (degenerative)

What do proteins determine?

organism's characteristics, traits

What is the purpose of rRNA?

makes up the ribosome

What is the role of the sigma factor?

to enable RNA polymerase to bind to the promoter

What is the DNA strand that is used as a template for transcription?

template strand

What is the DNA strand that is opposite of the template strand and identical to new RNA strand expect it has T's instead of U's ?

coding strand

What is the function of the promoter?

as a recognition site for the sigma factor so RNA polymerase can bind to DNA

What does conservative mean?

several codons specify same amino acids

What does redundant mean?

all amino acids coded by more than one codon

What does unambiguous mean?

single codon never codes for more than one amino acid

What does non-overlapping mean?

Each base is only read once