Translation

Question 1

define translation:

Answer 1

• synthesis of polypeptide, under direction of mRNA
• happens at ribosomes:
• from mRNA to amino acids

Question 2

codons: features

Answer 2

• only 20 amino acids, 4 nucleotide bases in DNA
• based off of triplet code (codons)
  = 64 codons to specify amino acids

Question 3

types of codons:

Answer 3

• found in mid 60s
• 61 for amino acids
• 3 for ‘stop’
• 1 to ‘start’ (AUG)

Question 4

redundancy:

Answer 4

• many codons code for a amino acid
• but not ambiguous
• 3rd codon position flexible (wobble)

Question 5

difference btw mRNA, tRNA, and rRNA:

Answer 5

mRNA: message which translate into protein

tRNA:
carries specific amino acid on one end
- anticodon on other end
- pairs with complementary codon on mRNA

rRNA:
- combine with proteins to form site of translation- ribosome

Question 6

transfer RNA: features

Answer 6

• single RNA strand, 80 nucleotides long

- has amino acid attachment site and anticodon end

Question 7

binding amino acid:

Answer 7

• matches correct amino acid with tRNA via aminoacyl-tRNA synthestases

Question 8

aminoacyl-tRNA synthetases:

Answer 8

protein which helps match amino acid with tRNA

- 20 synthetases (one for each amino acid)

Question 9

rRNA: features

Answer 9

• like tRNA, folds in on itself
• component of ribosome
• helps facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis

Question 10

ribosome:

Answer 10

made of large and small subunit

• proteins + rRNA
• has 3 bonding sites, APE

Question 11

binding sites of ribosome:

Answer 11

A: holds tRNA that carries next amino acid to be added to the chain
P: holds tRNA that carries growing polypeptide chain
E: exit site, where discharged tRNA leave ribome

Question 12

list stages of translation: and what aids this process

Answer 12

• initiation
• elongation
• termination

protein ‘factors’ aid all three stages

Question 13

initiation stage:

Answer 13

mRNA + initiator tRNA + 1st amino acid + 2 ribosomal subunits = initiation complex

Question 14

elongation stage:

Answer 14

• amino acids are added one by one to preceding amino acid
• each addition have ‘elongation factors’ (protein) and occurs in 3 steps:
• codon recognition
• peptide bond formation
• translocation

Question 15

termination stage:

Answer 15

• when stop codon reaches A site in ribosome

- release factor adds water molecule instead of amino acid

Question 16

polyribosomes:

Answer 16

many ribosomes can translate single RNA simultaneously forming polyribosome (or polysome)
- enable cell to make many copies of polypeptide quickly

Question 17

special bacteria only feature:

Answer 17

can transcribe and translate at the same time on same strand of DNA

Question 18

list types of mutations on nucleotide pairs:

Answer 18

• silent
• missense
• nonsense
• frameshift (insertion/ deletion)
• 3 nucleotide-pair deletion

Question 19

silent mutation:

Answer 19

change of a nucleotide in codon, doesn’t change amino acid produces= same polypeptide chain

Question 20

missense mutation:

Answer 20

change of a nucleotide causes different amino acid produced= different polypeptide chain

Question 21

nonsense mutation:

Answer 21

wrong nucleotide cause premature ending of polypeptide chain

Question 22

frameshift 1 nucleotide pair insertion mutation:

Answer 22

extra nucleotide changes rest of amino acids produced/ possible early stop

Question 23

frameshift 1 nucleotide pari deletion mutation:

Answer 23

shifts rest of codons, forms different amino acids = different polypeptide chain

Question 24

3 nucleotide pair deletion

Answer 24

one whole codon deleted, mostly same amino acids / and polypeptide chain produced, missing 1 amino acid

Question 25

which end does amino acids add to?

Answer 25

• added from carboxyl end

- start of polypeptide chain is on amino end