MTTC MTTC Biology 3 — Questions and Answers
Question 1: Which phase of meiosis is responsible for genetic recombination through crossing over?
- Metaphase I
- Prophase I (Correct answer)
- Anaphase II
- Telophase I
Correct answer: Prophase I
During Prophase I, homologous chromosomes synapse and exchange genetic material through crossing over at chiasmata.
Question 2: An enzyme's active site becomes permanently blocked by a molecule that resembles the substrate but cannot be released. This is:
- Competitive inhibition
- Allosteric regulation
- Irreversible inhibition (Correct answer)
- Feedback inhibition
Correct answer: Irreversible inhibition
Irreversible inhibitors form covalent bonds with the active site, permanently blocking enzyme activity.
Question 3: Which blood vessel type has walls only one cell layer thick, allowing gas and nutrient exchange?
- Arteries
- Veins
- Capillaries (Correct answer)
- Venules
Correct answer: Capillaries
Capillaries have walls composed of a single layer of endothelial cells, enabling efficient exchange of oxygen, CO2, nutrients, and wastes.
Question 4: In a dihybrid cross between two plants that are both RrYy (round yellow seeds), what fraction of offspring would be round and green?
- 1/16
- 3/16 (Correct answer)
- 9/16
- 1/4
Correct answer: 3/16
The RrYy × RrYy cross yields a 9:3:3:1 ratio; 3/16 of offspring are round (R_) and green (yy).
Question 5: Which hormone triggers the 'fight-or-flight' response by increasing heart rate and blood glucose?
- Insulin
- Cortisol
- Epinephrine (Correct answer)
- Glucagon
Correct answer: Epinephrine
Epinephrine (adrenaline), released by the adrenal medulla, rapidly prepares the body for emergency response by increasing heart rate, dilating airways, and raising blood glucose.
Question 6: A researcher finds that a species of fish in two isolated lakes have nearly identical morphology but cannot interbreed. These fish are best classified as:
- The same species with geographic variation
- Different subspecies
- Different species (Correct answer)
- Ecotypes of one species
Correct answer: Different species
Reproductive isolation is the defining criterion of species under the biological species concept; inability to interbreed means they are separate species.
Question 7: Which structural feature of the small intestine most directly increases surface area for nutrient absorption?
- Sphincters
- Rugae
- Villi and microvilli (Correct answer)
- Goblet cells
Correct answer: Villi and microvilli
Villi and microvilli (brush border) dramatically increase the absorptive surface area of the small intestine, allowing efficient nutrient uptake.
MTTC MTTC Biology 3
Which phase of meiosis is responsible for genetic recombination through crossing over?