Q: Exposure to what can increase the amount of pigment in the skin and make it appear darker? Read this paragraph and choose the correct option from the provided answers: Genes are a major determinant of human skin color. However, exposure to ultraviolet radiation can increase the amount of pigment in the skin and make it appear darker. Choices: - gamma rays - sunlight - nuclear radiation - ultraviolet radiation A:
ultraviolet radiation

Q: What distinctive configuration of dna demonstrates the base-pairing nature of the bases? Read this paragraph and choose the correct option from the provided answers: The double helical nature of DNA, together with the findings of Chargaff, demonstrated the base-pairing nature of the bases. Adenine always pairs with thymine, and guanine always pairs with cytosine ( Figure below ). Because of this complementary nature of DNA, the bases on one strand determine the bases on the other strand. These complementary base pairs explain why the amounts of guanine and cytosine are present in equal amounts, as are the amounts of adenine and thymine. Adenine and guanine are known as purines . These bases consist of two ring structures. Purines make up one of the two groups of nitrogenous bases. Thymine and cytosine are pyrimidines , which have just one ring structure. By having a purine always combine with a pyrimidine in the DNA double helix, the distance between the two sugar-phosphate backbones is constant, maintaining the uniform shape of the DNA molecule. Choices: - single helix - double loop - triple helix - double helix A:
double helix

Q: Mammals have a number of kinds of thermoreceptors, each specific for a particular what? Read this paragraph and choose the correct option from the provided answers: Choices: - electrical range - oxygen range - weight range - temperature range A:
temperature range

Q: By allowing blood levels of a hormone to be regulated within a narrow range, feedback loops contribute to maintaining what state? Read this paragraph and choose the correct option from the provided answers: Role of Feedback Loops The contribution of feedback loops to homeostasis will only be briefly reviewed here. Positive feedback loops are characterized by the release of additional hormone in response to an original hormone release. The release of oxytocin during childbirth is a positive feedback loop. The initial release of oxytocin begins to signal the uterine muscles to contract, which pushes the fetus toward the cervix, causing it to stretch. This, in turn, signals the pituitary gland to release more oxytocin, causing labor contractions to intensify. The release of oxytocin decreases after the birth of the child. The more common method of hormone regulation is the negative feedback loop. Negative feedback is characterized by the inhibition of further secretion of a hormone in response to adequate levels of that hormone. This allows blood levels of the hormone to be regulated within a narrow range. An example of a negative feedback loop is the release of glucocorticoid hormones from the adrenal glands, as directed by the hypothalamus and pituitary gland. As glucocorticoid concentrations in the blood rise, the hypothalamus and pituitary gland reduce their signaling to the adrenal glands to prevent additional glucocorticoid secretion (Figure 17.6). Choices: - hypothesis - hibernation - consciousness - homeostasis A:
homeostasis