Microorganisms, immunity and biotechnology

Written by Dr. Hira Salman (Biology)

MDCAT · Biology · 7 questions

Name: ____________________ Date: ____________

Gram-positive bacteria appear which colour after Gram staining?
- A Colourless
- B Purple or violet
- C Pink or red
- D Green
Restriction enzymes are used to:
- A Make proteins
- B Join DNA fragments
- C Copy RNA
- D Cut DNA at specific sequences
The polymerase chain reaction (PCR) is used to:
- A Stain bacteria
- B Amplify a DNA sequence
- C Sequence proteins
- D Break down RNA
Penicillin was discovered by:
- A Robert Koch
- B Alexander Fleming
- C Edward Jenner
- D Louis Pasteur
A vaccine protects the body mainly by:
- A Killing bacteria directly
- B Supplying ready-made antibodies for life
- C Stimulating immune memory
- D Raising body temperature
HIV mainly attacks which cells?
- A Red blood cells
- B Neurons
- C Platelets
- D Helper T cells
Agrobacterium tumefaciens is used in genetic engineering to:
- A Transfer genes into plants
- B Kill plant viruses
- C Digest cellulose
- D Make insulin in animals

Answer key

1. B, 2. D, 3. B, 4. B, 5. C, 6. D, 7. A

Their thick peptidoglycan wall keeps the crystal violet stain, so they look purple. Gram-negative bacteria look pink.
Each restriction enzyme recognises a short DNA sequence and cuts there. Ligase is the enzyme that joins fragments.
PCR makes millions of copies of a chosen DNA segment by repeated heating and cooling cycles with a heat-stable polymerase.
Fleming noticed in 1928 that a Penicillium mould killed bacteria on his culture plate.
A vaccine shows the immune system a harmless form of the microbe, so memory cells form and respond fast to a real infection.
HIV infects CD4 helper T cells, which coordinate the immune response, so immunity gradually fails.
Its Ti plasmid can carry a chosen gene into plant cells, which is how many transgenic plants are made.