Question 19M.3.HL.TZ2.13
| Date | May 2019 | Marks available | [Maximum mark: 6] | Reference code | 19M.3.HL.TZ2.13 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Discuss | Question number | 13 | Adapted from | N/A |
Discuss the use of microarrays in the diagnosis of disease.
[6]
a. DNA spots/probes/sequences attached to solid surface/microarray ✔
b. mRNA from healthy tissue/cell isolated and converted to cDNA
OR
mRNA from cancer tissue/cell isolated and converted to cDNA ✔
c. conversion to cDNA by reverse transcriptase ✔
d. fluorescent dye linked to copy DNA/cDNA ✔
e. cancer cDNA colored with a different dye from the healthy cDNA ✔ Accept named colour.
f. cDNA binds to/hybridizes with probes that have complementary base sequences ✔
g. microarray rinsed to remove cDNA that has not hybridized ✔
h. microarray exposed to laser light which causes fluorescent dye to give off light ✔
i. fluorescence shows which probes have hybridized
OR
fluorescence shows which sequences were in the tissue/sample ✔
j. hybridized probe shows gene expression
OR
hybridized probe helps in diagnosis of disease ✔
k. infection by pathogen can be detected by presence of its genetic material ✔
Most candidates had some knowledge of microarrays and could outline the outcome of their usage; some answers nevertheless were not displayed in a very logical order, missing the details of hybridization. Many specified only DNA where cDNA should have been mentioned.
