Cleavage divisions proceed at approximately the same rate in the embryo of _______, reflecting
uniform distribution of yolk.
a. bird
b. human
c. sea urchin
d. frog
e. sea urchin and human
C
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Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce_____.
A) all sharp-spined progeny B) 50% sharp-spined, 50% dull-spined progeny C) 25% sharp-spined, 50% dull-spined, 25% spineless progeny D) all spineless progeny E) It is impossible to determine the phenotypes of the progeny.
When added to water at neutral pH (7.0), an acid will
a. act as a proton donor, raising the pH of the solution. b. act as a proton acceptor, raising the pH of the solution. c. act as a proton donor, lowering the pH of the solution. d. act as a proton acceptor, lowering the pH of the solution. e. do nothing since the aqueous solution is neutral.
Mendel's hypothesized that among round F2 seeds there was a 1 RR:2Rr genotype ratio and used a testcross to provide support for this idea. He took all round F2 seeds and planted them. He then crossed the mature plants to wrinkled (rr) plants. Which of the following predictions follows from his hypothesis?
A: All of the resulting F3 generation seeds will be round. B: Two-thirds of the plants will produce all round seeds. C: One-third of the plants will produce all round seeds. D: All of the above
Sickle-cell anemia is caused by a recessive mutation in the hemoglobin gene. However, heterozygote individuals also show a small percentage of sickled red blood cells. What type of inheritance pattern is this an example of?
A) Polygenic inheritance B) Sex linked C) Chromosomal nondisjunction D) Incomplete dominance