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Pearson Edexcel IAL Biology 6.18 Gel electrophoresis of DNA fragments

Practise gel electrophoresis questions on DNA fragment movement, gel concentration, band position and simple rate calculations.

Syllabus
First assessment 2019
Course
Biology YBI11
Level
A2

Exam points

  • predict band position on a gel from fragment molecular weight and relative movement
  • explain slower fragment movement in concentrated gel using pore size, resistance or friction
  • use a given equation or table to calculate relative movement or fragment molecular weight

6.18—Gel electrophoresis of DNA fragments question 1

[Maximum number: 2]

Gel electrophoresis is used to separate DNA fragments of different lengths.
The rate at which the DNA fragments move through the gel depends on several factors including:
- molecular size of the DNA fragment
- shape of the DNA fragment
- concentration of the gel.

Question (a)

(a)

Fragments of double-stranded DNA move through the gel at a relative rate ( Mr\mathrm{M}_{\mathrm{r}} ) that is inversely proportional to the log of their molecular weight (MW).

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Question (i)

(i)

The diagram shows the position of a DNA fragment with a MW of 10000, after gel electrophoresis.

Complete the diagram to show the position of a DNA fragment with a MW of 100000.

Use the information in the question.

Figure for Question (i) — Edexcel A-Level Biology A2
[ 1 ]

Question (b)

(b)

The fragments move more slowly through a higher concentration of gel. Suggest why the fragments move more slowly through a higher concentration of gel.

[ 1 ]
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