DP Biology (last assessment 2024)

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Question 18M.3.HL.TZ2.a

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Date May 2018 Marks available [Maximum mark: 2] Reference code 18M.3.HL.TZ2.a
Level HL Paper 3 Time zone TZ2
Command term Explain Question number a Adapted from N/A
a.
[Maximum mark: 2]
18M.3.HL.TZ2.a

A DNA microarray chip was prepared as a collection of microscopic DNA strands from human genes attached to a solid surface. The diagram shows part of the microarray chip after hybridization with cDNA produced from normal cells and from cancer cells. cDNA of normal cells was labelled with green fluorescent dye and cDNA from cancer cells was labelled with red fluorescent dye. Both sets of labelled cDNA were then allowed to bind to the microarray.

Explain the reason that only cDNA from expressed genes binds to the DNA on the chip.

[2]

Markscheme

a. mRNA is purified from «normal and cancer» cells 

b. only expressed/transcribed genes produce mRNA 

c. cDNA is «a complementary DNA copy» synthesized from mRNA «by using reverse transcriptase/transcription»

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