What phenomenon explains the formation of rainbows in the sky?

Correct Answer: C

Rationale: Rainbows are formed due to the refraction and dispersion of sunlight by water droplets in the atmosphere. When sunlight enters a water droplet, it is refracted, then internally reflected, and finally refracted again as it exits the droplet. This dispersion of light into its component colors creates the beautiful rainbow we see in the sky. Choice A, diffraction, involves bending of light around obstacles or through narrow openings, not the splitting of light into colors as seen in rainbows. Choice B, interference, refers to the phenomenon where two or more light waves overlap and interact, producing a pattern of light and dark bands, which is not the case with rainbows. Choice D, reflection from clouds, does not accurately describe the process involved in the formation of rainbows through refraction and dispersion of light by water droplets.

Correct Answer: B

Rationale: Homozygous refers to an organism with two identical alleles for a gene, either both dominant or both recessive. Heterozygous, the correct answer, refers to an organism with two different alleles for a gene, one dominant and one recessive. Dominant and recessive describe the relationship between alleles, where dominant alleles are expressed over recessive alleles in heterozygous individuals. Therefore, the term for an organism with two different alleles for a gene is 'heterozygous.'

Correct Answer: D

Rationale: A) Karyotyping is a genetic test that examines an individual's chromosomes to detect abnormalities such as extra or missing chromosomes. It is not typically used to reveal an individual's susceptibility to certain diseases. B) Pharmacogenomics is the study of how genes affect a person's response to drugs. It focuses on how genetic variations can influence drug response, rather than susceptibility to diseases. C) Paternity testing is a genetic test used to determine the biological relationship between a child and an alleged father. It is not used to reveal an individual's susceptibility to diseases. D) Microarray analysis is a type of genetic testing that can reveal an individual's susceptibility to certain diseases by analyzing variations in their DNA. It can identify genetic markers associated with increased risk for specific conditions, allowing for personalized risk assessment and preventive measures.

Correct Answer: C

Rationale: The correct answer is C, the stomach. The stomach is responsible for churning and mechanically breaking down food. It contains muscles that contract and relax to mix food with digestive juices, breaking it down into smaller particles. This mechanical digestion process helps prepare the food for further digestion and absorption in the small intestine. The small intestine is primarily responsible for the absorption of nutrients, not for mechanical digestion. The large intestine absorbs water and salts, and the esophagus is a muscular tube that transports food from the mouth to the stomach, not involved in churning or breaking down food.

Correct Answer: D

Rationale: A) Gastrin is a hormone that stimulates the release of gastric acid in the stomach, not digestive enzymes from the pancreas. B) Insulin is a hormone produced by the pancreas that regulates blood sugar levels by facilitating the uptake of glucose into cells, but it does not directly signal the release of digestive enzymes from the pancreas. C) Glucagon is another hormone produced by the pancreas that works opposite to insulin by increasing blood sugar levels, but it is not involved in signaling the release of digestive enzymes from the pancreas. D) Secretin is a hormone released by the small intestine in response to the presence of acidic chyme. It stimulates the pancreas to release bicarbonate to neutralize the acidity of the chyme and also triggers the release of digestive enzymes from the pancreas to aid in digestion. Therefore, secretin is the hormone that signals the release of digestive enzymes from the pancreas.