DP Biology (last assessment 2024)

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Question 22M.2.HL.TZ2.5a.iii

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Date May 2022 Marks available [Maximum mark: 3] Reference code 22M.2.HL.TZ2.5a.iii
Level HL Paper 2 Time zone TZ2
Command term Outline Question number a.iii Adapted from N/A
a.iii.
[Maximum mark: 3]
22M.2.HL.TZ2.5a.iii

DNA forms chromosomes, but much of eukaryote DNA is non-coding.

[Source: Pixabay.]

(a.iii)

There are multiple tandem repeats of nucleotide segments of DNA found in the non-coding DNA between genes. Outline how tandem repeats are used for DNA profiling.

[3]

Markscheme
  1. tandem repeats (at one locus) vary in number of times sequence repeats / represent different alleles for one locus;
  2. DNA sample cut by restriction enzymes into fragments;
  3. samples of DNA are amplified at specific genetic sites with PCR;
  4. the fragments are separated by their size/number of repeats with gel electrophoresis;
  5. fluorescent/radioactive label attached to different tandem repeats;
  6. data from several loci at one time uniquely identify individuals / like a fingerprint, combinations of alleles are specific to an individual;
  7. comparisons/similarities between fragment patterns to determine paternity/evidence match to a suspect’s profile / other example of comparison/similarity;

OWTTE

Examiners report

There was a noticeable number of blank answers with respect to this question about using tandem repeats as the foundation of DNA profiling. Others had a good idea about PCR and gel electrophoresis, but many didn't mention restriction enzymes and did not clearly understand that patterns are compared.

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