James Watson and Francis Crick
a. established the double-stranded nature of DNA.
b. established the principle of base pairing.
c. explained how DNA's structure permitted it to be replicated.
d. proposed the concept of the single-helix.
e. discovered genes.
A
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The North American maggot fly diverged into two species because some individuals fed on apples rather than hawthorn trees. Apple fruit mature more quickly than hawthorn fruit, therefore maggot flies that fed on apples also developed more quickly. Pea aphids can feed on alfalfa or red clover; some aphids have higher fitness when eating clover others when eating alfalfa. Host preference can
eventually lead to speciation because A. genetic differences develop. B. lower fitness may result from choosing the wrong host. C. temporal isolation may occur. D. anagenesis may occur. E. genetic differences develop, higher fitness and temporal isolation may occur.
A hormone binds a receptor and activates the cAMP signal transduction pathway ultimately leading to the cell response. If you wanted to develop a drug to block this pathway, the drug would need to inhibit _____
A. hormone release from the receptor. B. adenylyl cyclase. C. protein phosphatases remove phosphates from proteins initially activated by protein kinase A. D. GTP on the alpha subunit of the G protein being hydrolyzed to GDP. E. phosphodiesterase.
What is the structure of telomeres?
A) short, repetitive DNA sequences found at the ends of linear eukaryotic chromosomes B) long, repetitive DNA sequences found at the ends of linear eukaryotic chromosomes C) short, repetitive DNA sequences found at the ends of linear prokaryotic chromosomes D) long, unique DNA sequences found at the ends of linear eukaryotic chromosomes
The seed is produced by the maturation of the
a. embryo. b. ovule. c. ovary. d. zygote. e. pollen.