Translation

Question 1

Purpose of Translation

Answer 1

to decode mRNA and make the functional protein product of the gene

Question 2

Where does translation occur in euk?

Answer 2

in cytoplasm and must be exported out of nucleus (where transcription happens)

Question 3

What is a polypeptide?

Answer 3

long chain of AA sequence (peptide bonds) - (NH3+ terminal, COO- terminal, and side group) = 1 gene

Question 4

How did they test for one AA at a time?

Answer 4

Homopolymer is added to the test tube which checks for radioactivity

Question 5

How did they identify AA specified by mixed codons? - Short mRNA of known sequences stimulate the binding of (blank) and correspond (blank) bound (blank).

Answer 5

Short mRNA’s of known sequences stimulate the binding of ribosomes and correspond AA bound tRNA

Question 6

Why is there degeneracy?

Answer 6

The wobble position in the anticodon (tRNA) is at the 5’ end (1st position) reduces the number of tRNA

Question 7

3 main elements for translation - ribosomes

Answer 7

• prok = large (50S), small (30S), complex(70S)
• euk = large (60S), small (40S), complex (80S)

Question 8

3 main elements for translation - aminoacyl tRNA synthetase- Why does each aa have its own? Where does the enzyme attach to and what does it do to the tRNA? How does it charge it? Once the AMP is released what gets added?

Answer 8

Each AA has its own because they’re very specific (20), enzyme attaches to the 3’ end of tRNA and charges it.
- charges it with AMP, then releases the AMP, and adds AA

Question 9

3 main elements for translation - transfer RNA- What are the adaptors between AA and codons in mRNA? How does it attach to the 3’ end resulting in a tRNA change?

Answer 9

• (CCA) - adaptors between AA and codons in mRNA
• covalently attaching 3’ end of tRNA is how we change tRNA

Question 10

Translation (similar in euk and prok) - Initiation (prok) IF-1, IF-2, IF-3

Answer 10

• IF-1 and IF-2 position ribosome over start codon and IF-3 prevents large subunit from binding.

Question 11

Translation (similar in euk and prok) - Initiation (euk) Where does the complex form and what does it influence?

Answer 11

Complex forms at 5’ end of mRNA and the Kozak sequence (GCCRCCATGG) influences efficiency of which aUG is used to start translation

Question 12

Translation (similar in euk and prok) - Initiation (prok) What site does F-met occupy?

Answer 12

F-met (just met in euk) occupies P site of ribosome

Question 13

Translation (similar in euk and prok) - Initiation (prok) Where does complex form?

Answer 13

Shine Dalgarno sequence

Question 14

Translation (similar in euk and prok) - Initiation (prok) What does GTP do?

Answer 14

GTP releases complex from tRNA

Question 15

Translation (similar in euk and prok) - Initiation (euk) What promotes translation in euk?

Answer 15

Poly A tail and 7MG cap promotes translation

Question 16

Translation (similar in euk and prok) - Elongation - Where does EF-tu place the charged AA-tRNA?

Answer 16

Into the A site of the ribosome

Question 17

Translation (similar in euk and prok) - Elongation - Where does the EF-G move the ribosome? And what does tRNA release? In what site?

Answer 17

Toward the 3’ end of mRNA and releases tRNA in P site from its AA

Question 18

Recap of Ribosome site - where does AA enter?

Answer 18

A site

Question 19

Recap of Ribosome site - what site contains the growing polypeptide chain?

Answer 19

P site (f met starts here)

Question 20

Recap of Ribosome site - What site exits into cytoplasm?

Answer 20

E site

Question 21

How does polypeptide chain grow?

Answer 21

N terminal to C terminal

Question 22

What direction does the ribosome move down mRNA?

Answer 22

5’ to 3’ direction

Question 23

Translation (similar in euk and prok) - Termination - What do RF 1, RF 2, and RF 3 do?

Answer 23

RF-1 (UAA/UAG) and RF-2 (UAA/UGA) interact with stop codons and RF-3 bind to GTP and involved in dissociation of ribosomal complex.

Question 24

Translation (similar in euk and prok) - Termination - When does termination happen?

Answer 24

When a stop codon enters A site of ribosome - no tRNAs to bind - so a release factor binds to A site