A stem cell is an undifferentiated cell from which specialized cells such as muscle and nerve can be formed.
a. true
b. false
Answer: a. true
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Which of the following statements is true regarding Wolbachia bacteria?
A. Wolbachia co-evolved with insects. B. Wolbachia can selectively kill male insect embryos. C. Wolbachia can convey Dengue-resistance in insects. D. Wolbachia can affect the reproductive structures of its insect hosts. E. All of these statements about Wolbachia are true.
During the first 5–600 million years on Earth, temperatures ranged from 500–1000°C, atmospheric pressure was 10 times current levels, and the planet was bombarded with meteorites. How would these conditions favor the formation of biological molecules?
A. Many chemical reactions are inhibited by high temperature and pressure. B. High temperature and pressure are the best conditions for enzyme function, needed to support life. C. Oxygen will break down many organic molecules by reduction. D. Oxygen in this high temperature and pressure atmosphere would have been chemically less reactive. E. Water and meteorite dust would have provided the chemical reactions necessary for formation of biological molecules.
What genotype would be found in an individual who is a carrier for a recessive genetic disorder but does not have symptoms of the disorder?
A) heterozygous B) homozygous for the recessive allele C) homozygous for the dominant allele D) either homozygous for the recessive allele or heterozygous
Which of the following stimulates fibroblasts to proliferate and thus heal a wound?
a. EGF b. NGF a. NO d. PDGF