John Bernal suggested that prebiotic synthesis of polymers took place on clay because
A. Clay minerals are known to bind organic molecules.
B. Clay is negatively charged and attracts cations.
C. Some minerals in clay attract organic monomers and catalyze chemical reactions.
D. Clay minerals can attract and bind organic molecules, catalyze chemical reactions and attract cations.
E. Clay is positively charged and can bind organic molecules for polymerization.
D. Clay minerals can attract and bind organic molecules, catalyze chemical reactions and attract cations.
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In an isolated population of fruit flies, 4 percent of the individuals have "pink eyes", a homozygous
recessive condition, and 96 percent have the dominant black eye phenotype. What percentage of the population are heterozygotes?
a. 32 percent b. 16 percent c. 48 percent d. 88 percent e. 4 percent
Which plants resemble palm trees (but are not close relatives), and contain toxins that increase the risk of neurodegenerative disorders and cancer?
a. tree ferns b. conifers c. gnetophytes d. ginkos e. cycads
The accompanying graph shows a growth curve of E. coli growing in a defined medium containing equal molar amounts of glucose and lactose
Based on your knowledge of the regulation of the lac operon, the best explanation of these results is that A) early on, due to the presence of lactose, the bacteria use the lac operon. Glucose is used later. B) the bacteria use both sugars simultaneously. C) the presence of glucose causes the formation of cAMP catabolic repressor protein (CRP) complexes, which shut down the lac operon until the glucose is used up. D) glucose is used first. Once glucose becomes limiting, intracellular cAMP increases, forming cAMP–CRP complexes that activate the lac operon to use lactose. E) early on the glucose binds to the repressor protein lacI and shuts down the lac operon.
Which of the following statements about Candida is FALSE?
A. It is present in the digestive tract of 40-80% of all healthy individuals. B. It can be transmitted to adults during sexual contact. C. It is easily treated with topical antifungals in immunocompromised patients. D. It causes thrush. E. It can be passed to babies during childbirth.