AP Bio - Ch.14: Gene Expression from Gene to Protein

Transcription

Synthesis of RNA during DNA information

mRNA

RNA transcribed and made from the template strand. Specifies protein’s primary structure.

Translation

Synthesis of a polypeptide using mRNA information

rRNA

Molecular complexes facilitating orderly linking of amino acids into polypeptide chains (sites of translation)

tRNA

Translates mRNA codon with anticodon recognition and transfers the corresponding amino acid during polypeptide synthesis

Codons

Codes for 1 amino acid ; made up of 3 nucleotides

RNA polymerase

Enzyme that pries DNA open; elongates and joins the RNA nucleotides complementary to it

Transcription Initiation

____ ____ is started by RNA polymerase attaching to a promoter, (TATA box).

• Transcription factors must attach first to template strand in order for polymerase to attach in Eukaryotes

• Prokaryotes can transcribe freely without limitations (less complex DNA)

Transcription Elongation

____ _____ occurs when RNA polymerase adds on to the 3’ end and untwists the DNA as the polymerase proceeds. RNA will “peel” away from DNA template strand as the elongation process continues

Transcription Termination

____ _____ occurs when the mRNA transcribed is “AAUAAA”

• in Eukaryotes: polyadenylation signal — terminates transcription 10-35 nucleotides downstream after

• in Prokaryotes: immediately ends process

5’ cap

RNA processing involves adding a modified form of Guanine (_____) to the end of the 5’ of the mRNA synthesized.

3’ poly-A-tail

RNA processing involves adding a sequence of 50-250 (______) to 3’ end of mRNA synthesized

Introns

Eukaryotes undergo RNA processing while prokaryotes don’t because of Eukaryote’s DNA being stored in a nucleus and their mRNA’s presence of _____

Translation Initiation

____ ______ starts when rRNA recognizes mRNA and binds to its 5’cap. The tRNA inside it scans till it finds start codon (AUG) and hydrogen bonds there

Translation Elongation

_______ _______ occurs through tRNA (carrying the next amino-acid to be added) binding at the A site

• P-site: where tRNA holding growing peptide chain binds

• E-site: where tRNA gets discharged and leaves the ribosome

Translation Termination

_______ ______ occurs when a release factor is accepted at the A-site.

• tRNA’s bond to the rRNA is broken and it’s released

• Amino acid gets released as well

• rRNA subunits get disassembled

mutagens

Chemical or physical agents that interacts with DNA and causes a mutation

Silent Mutation

Small-scale mutation (resulting from an incorrect substitution of a single nucleotide base) of no observable phenotype change

(Changed codon still codes for the same amino acid)

Missense Mutation

Small-scale mutation (resulting from an incorrect substitution of a single nucleotide base) that leads to coding for a different amino acid

Nonsense Mutation

Small-scale mutation (resulting from an incorrect substitution of a single nucleotide base) where the changed codon is now a stop codon → terminates the translation process early

Frameshift Mutation

An extensive mutation, resulting from an insertion/deletion of a single nucleotide base, where all codons are from then on grouped incorrectly downstream from the error → all amino acids from then on get synthesized incorrectly