Humans have an extremely high level of genetic similarity, with greater than 99% sequence identity across populations. Yet, many people appear very different phenotypically. How do you reconcile these observations?
What will be an ideal response?
These observations are very easily reconciled. The phenotypic differences are actually genetically trivial. Differences in body shape, skin color, eye color, body shape, and so on, undoubtedly result from variation in a scant few coding loci. In addition, much phenotypic variation is caused by environmental factors, such as nutrition. The human genome consists of some three billion nucleotides, so the few loci that underlie phenotypic differences constitute so trivial a subset of these that geneticists generally do not accept the idea of a genetic basis for "race."
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Which of the following are absorbed by the
lymphatic system? a. monosaccharides b. amino acids c. triglycerides d. nucleic acids e. proteins
Leptin is a circulating hormone that is produced by fat cells and plays a role in body metabolism and obesity. It normally binds to receptors in the brain and inhibits appetite. Studies have demonstrated that when obese mice that are leptin deficient are injected with leptin they quickly lose their excess weight. Interestingly, however, many overweight people have high levels of leptin in their bloodstream. Why do you think that the high levels of leptin in obese individuals are insufficient to curb their appetite?
A. In obese people with high levels of leptin, the leptin is a non-functional second messenger. B. The form of leptin released by obese people may lack protein kinase activity. C. Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity. D. Paracrine signaling may be disrupted in obese people with high levels of leptin.
The biological species concept:
a. states that any organisms that are biologically similar constitute a species. b. states that a species is any group that shares similar DNA. c. is infrequently used because it is inapplicable to many organisms. d. defines a species as any group of actually or potentially interbreeding species that produce viable offspring. e. is the best and most accurate species concept.
What is so particular about the onset and course of meningococcal meningitis?
A) The incubation time for this type of bacteria is always 30 days. B) Resulting diarrhea is particularly bloody if not treated within the first 24 hours. C) If not treated, death can occur within hours of fever onset. D) Bacteria are only spread through contact with sweat. E) Rash begins on patient extremities and spreads to the torso as patient itches.