MTTC Biology Flashcards

Which phase of meiosis is responsible for genetic recombination through crossing over?

Answer: Prophase I

During Prophase I, homologous chromosomes synapse and exchange genetic material through crossing over at chiasmata.

An enzyme's active site becomes permanently blocked by a molecule that resembles the substrate but cannot be released. This is:

Answer: Irreversible inhibition

Irreversible inhibitors form covalent bonds with the active site, permanently blocking enzyme activity.

Which blood vessel type has walls only one cell layer thick, allowing gas and nutrient exchange?

Answer: Capillaries

Capillaries have walls composed of a single layer of endothelial cells, enabling efficient exchange of oxygen, CO2, nutrients, and wastes.

In a dihybrid cross between two plants that are both RrYy (round yellow seeds), what fraction of offspring would be round and green?

Answer: 3/16

The RrYy × RrYy cross yields a 9:3:3:1 ratio; 3/16 of offspring are round (R_) and green (yy).

Which hormone triggers the 'fight-or-flight' response by increasing heart rate and blood glucose?

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.

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:

Answer: Different species

Reproductive isolation is the defining criterion of species under the biological species concept; inability to interbreed means they are separate species.

Which structural feature of the small intestine most directly increases surface area for nutrient absorption?

Answer: Villi and microvilli

Villi and microvilli (brush border) dramatically increase the absorptive surface area of the small intestine, allowing efficient nutrient uptake.