The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population's gene pool?
A) heterozygote advantage
B) stabilizing selection
C) diploidy
D) balancing selection
Answer: C
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The long extension of a cell that can propel a cell forward by whipping back and forth (such as human sperm) is called a ________.
A. flagellum B. vesicle C. cilium D. pilus
Which of the following occurs during metaphase
A. heterochromatin is converted to euchromatin. B. chromosomes are about 30 nm wide. C. chromosomes are much shorter than they were in interphase. D. chromosomes undergo gene transcription. E. the "beads on a string" structure is visible.
Parasitized caterpillars eating more alkaloid-rich food in order to poison their parasites is an example of _____
a. behavioral plasticity b. social plasticity c. epigenetics d. learned behavior e. mirroring
The first committed step of Krebs cycle is:
a. acetylCoA synthesis b. oxaloacetate regeneration c. citrate synthesis d. isocitrate dehydrogenation e. pyruvate decarboxylation