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Question 23M.3.HL.TZ2.14

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Date May 2023 Marks available [Maximum mark: 4] Reference code 23M.3.HL.TZ2.14
Level HL Paper 3 Time zone TZ2
Command term Describe, State Question number 14 Adapted from N/A
14.
[Maximum mark: 4]
23M.3.HL.TZ2.14

The sequence alignment shows the first 40 amino acids of adult and fetal hemoglobin in humans.

(a)

State the number of amino acids that these sections of adult and fetal hemoglobin have in common.

[1]

Markscheme

28

Examiners report

Most could correctly state the number of amino acids, but some did not count exactly.

(b)

Describe how a sequence alignment can be obtained and used to compare proteins.

[3]

Markscheme
  1. amino acid sequence obtained (in FASTA format);
  2. (alignment obtained by) BLASTp/CLUSTAL W/COFFEE / any named software;
  3. (sequence alignment) allows comparison of sequences (from different organisms)
    OR
    similar sequences are aligned next to each other;
  4. the percentage sequence similarity can be calculated;

“p” must be written in BLASTp.

Examiners report

Describing how sequence alignment could be obtained was difficult for most, although many mentioned BLASTp.