AP Biology - 6.3, 6.4 Transcription, RNA Processing, + Translation

what is the central dogma of biology?

genetic info flows from DNA → RNA → Protein

what is transcription?

process where enzyme directs the formation of an mRNA molecule

where does transcription occur?

nucleus

what are the first few step of transcription?

• DNA strands sep. into template strand + non-template strand

• RNA polymerase reads DNA from 3’ to 5’ and synthesizes mRNA in the 5’ to 3’ direction

• pre-mRNA produced

what are other terms for the template strand?

minus, antisense, noncoding

what are other terms for the non-template strand?

• positive, sense, coding

what is the role of the coding strand in transcription?

• serves as a reference b/c has the same nucleotide sequence as resulting mRNA other than U replacing T

what occurs in RNA processing?

• necessary for mRNA to leave nucleus

• on 5’ end, GTP cap added

• on 3’ end, Poly A-Tail added

• splicing (or alternative splicing)

what is the result of RNA processing?

a mature mRNA molecule

benefits of poly-A tail?

• increased stability

• helps w/ export from nucleus

benefits of GTP cap?

• protects transcript

• helps ribosome attach to mRNA

what are introns and extrons?

• introns - mRNA sequences that don’t code for AAs

• exons - mRNA sequences that do code for AAs

ID splicing:

• carried out by splycosomes

• exons retained in mRNA but introns spliced out

• alternative splicing - when specific exons are selected → more protein variety from smaller gene #

what is mRNA?

• messenger RNA

• carries genetic info from DNA to ribosomes and directs protein synthesis

• carries codons

what is tRNA?

• transfer RNA

• helps create specific polypeptide sequence, as directed by mRNA, in ribosomes

• e/a mol carries a diff amino acid

• carry anticodons

what is rRNA?

• ribosomal RNA

• units of RNA responsible for protein assembly

• base pairing occurs her and creates primary polypeptides

what is translation?

process by which an mRNA sequence is used to generate a polypeptide

what occurs in translation?

• mature mRNA attaches to ribosome

• goes through A, P, E active sites

• tRNA mols try and base-pair

• successful BP → more tRNA mols → peptide bond b/w amino acids of tRNA mols.

• stop codon will bring release factor to ribosome to prevent binding

after transcription, what happens to the resulting polypeptide?

• it goes to the golgi apparatus, undergoes folding to get tertiary structure

• becomes functional protein

where does translation occur?

• cytoplasm

what are three sites on the ribosome?

• E - exit (of tRNA)

• P - peptide bonding site

• A - arrival

what are the stages of translation?

• initiation, elongation, termination

ID initiation:

• when rRNA in ribosome interacts with mRNA at first start codon

• tRNA mols bring correct AA to correct place, as specified by mRNA codon

ID elongation:

• e/a new tRNA brings another AA to add to the growing polypeptide chain

ID termination:

• AAs keep adding until stop codon reached

• new polypeptide released

base pairing occurs b/w what?

• codons - on mRNA, set of 3 nucleotides

• anticodons - on tRNA, set of corresponding 3 nucleotides

what is retrovirus translation?

the alternate flow of info, involves viral RNA introduced into host cells

role of reverse transcriptase in retrovirus translation?

• copies viral RNA into viral DNA

• once converted, DNA integrated into host genome → transcription + translation → new viral progeny

what is evidence of common ancestry of all organisms?

• the genetic code is nearly universal

• similar translation mechanisms - where nucleotides used for DNA + RNA construction

fill in the blank: viral DNA and RNA molecules are chemically -(1)- with host-cell genomes and host-cell translation mechanisms work w/ -(2)- genomes

(1) compatible

(2) viral