1.ง่าย
What does DNA replication produce?
- ATwo identical DNA molecules
- BFour different DNA molecules
- COne mRNA molecule
- DA new protein
2.ง่าย
What does the polymerase chain reaction (PCR) do?
- AIt separates proteins by their charge
- BIt turns RNA into protein
- CIt cuts DNA at specific sequences
- DIt makes many copies of a piece of DNA
3.ง่าย
What are the parts of a triglyceride (a fat molecule)?
- AOne glycerol and three fatty acids
- BOne amino acid and three fatty acids
- CTwo glycerols and one fatty acid
- DThree glucose units and one phosphate
4.ปานกลาง
A seedling is 4 cm tall at week 1, 8 cm at week 2, 12 cm at week 3 and 16 cm at week 4. If the trend continues, how tall will it be at week 6?
- A32 cm
- B20 cm
- C18 cm
- D24 cm
5.ปานกลาง
Red-green colour blindness is X-linked recessive. A colour-blind woman (XᵇXᵇ) has children with a man with normal colour vision (XᴮY). What fraction of their sons is expected to be colour-blind?
- ANone
- BOne half
- COne quarter
- DAll
6.ปานกลาง
Why does each type of virus infect only certain kinds of cells?
- AIt must find cells with the same DNA as its own
- BIt must attach to specific receptor proteins on the cell surface
- CIt can only enter cells that have no nucleus
- DIt can only enter cells that are dividing by meiosis at that time
7.ยาก
A leaf with green and white areas is kept in light and then tested with iodine. Only the green areas turn blue-black. What does this show?
- AWhite areas store more starch than green areas
- BChlorophyll is needed for photosynthesis
- CLight is not needed for photosynthesis
- DIodine destroys chlorophyll in the leaf
8.ยาก
The antibiotic tetracycline binds to bacterial ribosomes. Which process does it block, and why are human cells much less affected?
- ADNA replication, because bacteria have no DNA polymerase
- BTranscription, because human cells have no RNA polymerase of their own
- CTranslation, because human cells have no ribosomes
- DTranslation, because bacterial ribosomes differ from human ribosomes
เฉลย
- 1. A · Two identical DNA molecules
- 2. D · It makes many copies of a piece of DNA
- 3. A · One glycerol and three fatty acids
- 4. D · 24 cm
- 5. D · All
- 6. B · It must attach to specific receptor proteins on the cell surface
- 7. B · Chlorophyll is needed for photosynthesis
- 8. D · Translation, because bacterial ribosomes differ from human ribosomes
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