In mammals, an egg fertilized by one sperm divides repeatedly (1-2-4-8-16-32-64, etc.). At the 64-cell stage, only three cells go on to become the embryo while 61 grow to become the fetal side of the placenta. In plants, fertilization likewise results in the development of an embryo and nourishing endosperm. However, how does this process differ from the mammal embryo and placenta?
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Answers may vary. In mammal embryos, a single haploid sperm fertilizes a single haploid egg to form a diploid zygote which undergoes multiple cellular divisions to produce an embryo. In angiosperms which are the dominant plants today, double fertilization occurs. A haploid sperm fertilizes a haploid egg to produce a diploid zygote which develops into the embryo. Another haploid sperm fertilizes the two polar nuclei of the central cell to produce a triploid endosperm. In both mammals and angiosperms, the embryo is protected and provided with nutrients.
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Which of the following pathways for complement activation is generally dependent upon the formation of antigen-antibody complexes?
A. Classical pathway B. Lectin complement pathway C. Alternative pathway D. All of the choices are correct.
Proponents of ________ [two words] argue that the complexities of living systems can only be accounted for by the creative acts of a conscious entity
Fill in the blank(s) with correct word
The first attempts at gene therapy began in 1990 with the treatment of a young girl with a genetic disorder abbreviated SCID. What does SCID stand for? In the context of SCID, what does ADA stand for?
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The most common disease diagnosed in humans that is caused by Cryptococcus is
A) primary pulmonary cryptococcosis. B) cryptococcal meningitis. C) secondary pulmonary cryptococcosis. D) cryptococcoma. E) cutaneous cryptococcosis.