Question 21M.2.SL.TZ1.6b
| Date | May 2021 | Marks available | [Maximum mark: 7] | Reference code | 21M.2.SL.TZ1.6b |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | b | Adapted from | N/A |
Cells produce a large variety of proteins with different sequences of amino acids. Explain how this is done.
[7]
a. protein is produced when a gene is expressed / switched on ✔
b. genetic code/codons consists of three nucleotides/bases/base triplet ✔
c. genetic code in DNA is transcribed/transcription (to mRNA) ✔
d. mRNA exits the nucleus ✔
e. mRNA (code) is translated/translation into a polypeptide/protein ✔
f. amino acid sequence/polypeptide formation occurs at a ribosome ✔
g. one codon translates to one amino acid ✔
h. tRNA carries code for specific amino acids ✔
i. tRNA anticodon matches with specific codon in mRNA ✔
j. amino acids joined (by peptide bonds) to form polypeptide ✔
k. sequence of amino acids determined by order of bases/nucleotides/codons in DNA/mRNA ✔
l. proteins vary based on which amino acids are used and their order
OR
protein variety increases by mutations to DNA ✔
This question was attempted by about 42 % of candidates.
Some brilliant, clear answers were given earning the maximum marks. However, coherent essays explaining protein synthesis were rare. Some students dwelled on transcription without ever mentioning translation. Codons, anticodons and their locations were not clearly understood. Valid information did appear but it was frequently mixed up or incomplete.
