UNIT STUDY: Translation

Question 1

What is translation

Answer 1

• Process where mRNA is used to synthesize a polypeptide
• Takes place in cytoplasm

Question 2

What is involved in translation (6 things)

Answer 2

1. mRNA: contains codons (sequence of 3 nucleootides that code for particular AA)
2. tRNA: transfer RNA - brings AA to ribosome. contrains anticodon (sequence of 3 nucleotides comlimenty to mRNA)
   - Legs of tRNA read mRNA, top attactches coresponding AA
3. Ribosome: made of rRNA and protiens, found in cytoplasm and has two subunits that hold mRNA and tRNA together during translation
4. tRNA ligase: enzye that adds AA to appropriate tRNA of cytoplasm (creates bond between top of tRNA and AA
5. Free AA: avalabile in cytoplasm, used to create polypeptides
6. Termination factor: molecule that reconizes specific sequence on mRNA, stop codon and stops tranlstaion

Question 3

What happens in initiation - translation

Answer 3

The small ribosomal subunit binds to the 5’ end of mRNA
A tRNA molecule carrying the amino acid methionine recognizes the start codon on mRNA (a sequence of AUG)
The anticodon on the tRNA is complementary to the codon on mRNA, and temporarily forms H-bonds between the nucleotides
With the input of energy, the large ribosomal subunit joins with the tRNA now in the P-site of the large subunit - together, this forms the translation initiation complex

Question 4

What happens in elongation - translation

Answer 4

Codon recognition: the codon in the A-site of the ribosome pairs with the appropriate tRNA molecule
Peptide bond formation: the two amino acids are linked
Amino acid chain from the tRNA in the P-site becomes bonded to the amino acid on the tRNA in the A-site
Translocation: tRNA in P-site moves to E-site (exits ribosome), tRNA in A-site moves to P-site - both tRNA move left

Question 5

What happens in termination - translation

Answer 5

Occurs when one of the three stop codons (UAA, UAG, UGA) arrives in the A-site
A release factor binds to the A-site, causing the whole thing to fall apart
The large and small ribosomal subunits separate from each other and from the mRNA
The new protein is released and can now fold into its 3D shape and get to work in the cell

Question 6

What is a genetic code

Answer 6

Triple codon = genetic instructions for a polypeptide chain are written in DNA as a series of three nucleotide words
Example: AGT on DNA will transcript UCA on mRNA, which codes for the amino acid serine

Question 7

What is the wobble hypothisis

Answer 7

Wobble hypothesis: only the first and second nucleotides are important

Question 8

What are codons

Answer 8

• DNA encodes a sequence of non-overlapping base triplets - codons
• Translation only begins when the start codon is read and stops when the stop codon is reached

Question 9

What does a sequence of AA become

Answer 9

Functional protien

Question 10

What is termination - translation

Answer 10

Occurs when one of the three stop codons (UAA, UAG, UGA) arrives in the A-site
A release factor binds to the A-site, causing the whole thing to fall apart
The large and small ribosomal subunits separate from each other and from the mRNA
The new protein is released and can now fold into its 3D shape and get to work in the cell