L10 Transl

Question 1

LO2: contrast diff types RNA: m/r/tRNA. Euk

Answer 1

• rRNA- over 80%. Few kinds only. Many copies of each. Made by RNAP I.
• mRNA- 2%. 100000s kinds. Few copies each. Made by RNAP II.
• tRNA- 15%. 100 kinds. LOT copies each. Made by RNAP III.
• mRNA few copies each as makes more ports, Euk only. Only 25k genes. Genes can make more than one mRNA. Init sig. Could be diff ones used at diff times. Init diff posits in prom. Splicing in Euk= complex gene regul. Somet leave intron in. Termin transc can vary.
• rRNA- ribos= prot and RNA complex.

Question 2

LO3: comp and contr prok vs Euk.

Answer 2

-prok- 3rRNAs and 56 prot. 30S and 50S= 70S ribos 20nm.
-Euk- 4 rRNA and 82 prot. 40S and 60S= 80S, 32nm.
Eg AB ca targ 30 not 40S.
-transl more diffic as nt to AA seq. 4 letter to 20 letter code. Adap molec req.
-bact- diff proms. Diff TFs. 1 RNAP comp to 3 Euk. Coupled transc/l- immed, no nuc, no maturation or transf. No post transc proc, no introns. Short lived mRNAs-deg fast, only, message, not stable, make as need. Simpler ribos. Distinct transl init, diff transl facs.
-tetracycline blocks bind of aatRNA to P site and codon.
Chloramphenicol block pep bond format.
Erythromycin blocks transloc.

Question 3

LO4: expl nat of triplet code and apply genet code.

Answer 3

-genet code is triplet as 4 letter to 20 letter. Triplets= non overlap and no gaps. Change Lang= 5’ to 3’ templ read through prod N to C pp chain exten.

Question 4

LO5: compreh implics of degen of genet code.

Answer 4

-same AA encod by more than one codon. 64 poss compons codons. Eg tryp and met only 1, alanine 4.
Init codon AUG=met. Termin UAG, UAA, UGA.
-tRNA adapter- stem loop. Ss specif fold, complem anti paral H bond. CCA termin at 3’, anticodon loop. Uncharged w/o AA.
-changed AA tRNA- base and aminoacyl grp added to 3’OH via P grp. Give energ.
-codon recog- eg Met codon AUG so tRNA anticodon CAU. Met on adenine at 3’.
-Wobble- Alanyl tRNA anticodon 5’ IGC recog said codons 5’ GCU/C/A. Inosine aspecif, can recog and H bond U/C/A in codon so 1 tRNA recog more than 1 codon. Also G to U in RNA.

Question 5

LO6: predic effs of var mut in a gene.

Answer 5

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Question 6

LO7: expl how muts outside coding reg can aff gene exp.

Answer 6

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Question 7

LO1: desc proc and role of transl.

Answer 7

-init- AUG recog by specif tRNA. Ribos form.
Elong- N to C chain growth. AatRNA build blocks. MRNA read 5’ to 3’.
Termin- stop codon and ribos dissoc.
-tRNA synthet are forms aatRNA. Each specif for an AA. Bind ATP and specif tRNA with anticodon. Connec AA, rel AMP and PPI, energ dep.
-pep bond- loss water.
-INIT- cap BPs, IFs, 40S, met tRNA and GTP in. Recog 5’ cap. Move along to AUG, uses ATP. Anticodon complem=stop. 60S in. GDP, IF, capBP out.
-ELONG- met tRNA in P site. New codon exposed and recog by aatRNA which binds using GTP. A accept aatRNA energ dep. Met pep bonds to second AA in A site tRNA. Uncharged tRNA leaves P. Transloc of ribos uses GTP- aatRNA with pp moves to P.
-Polypeptidyl transferase forms the pep bond. Rem AA bound to P site tRNA onto A site one= 2 AA and grows= peptidyl tRNA.
-TERMIN- when STOP codon in A site=tRNA mimic in. Recog stop, rem pep chain, free up uncharged tRNA. Hydrol pep bond.
-prot synth- polyribos/polysome. Lot on 1 mRNA. Prot chain prog longer. Ribos not specif-can read and transl any mRNA. Prot out, forms levs of struc, post transl modif.