Which component of the influenza virus is required for the initial attachment to human respiratory epithelial cells?
a. capsid protein
b. hemagglutinin
c. phospholipid
d. matrix protein
Answer: b. hemagglutinin
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You expect that a mutation in E. coli that was recently isolated results in loss of enzyme R activity. In looking for the gene, you find comparable sequences. Using an in vitro transcription translation system, you use the gene obtained from the mutant, as well as a wild type E. coli as a control. Following protein isolation and gel electrophoresis, you observe that the wild type E. coli produces
a protein that is 35K in size, corresponding to enzyme R. However, the mutant strain produces a protein that is 25K in size. What does this information suggest? A) A nonsense mutation has occurred, resulting in a truncated, nonfunctional product in the mutant. B) A large addition has occurred in the wild type strain, such that approximately 35 tandem repeats of this gene are present and are biologically active. C) A missense mutation has occurred, resulting in a truncated, nonfunctional product in the mutant. D) all of the above E) Not enough information is given.
The influence of testosterone on undifferentiated spermatogonia and Sertoli cells results in the hormone dictating
A) mitosis in immature sperm. B) rate of sperm production. C) when and how much LH and FSH are released. D) the production of ADH. E) the occurrence of ovulation.
A crayfish is a member of the phylum
A) Echinodermata. B) Mollusca. C) Annelida. D) Platyhelminthes. E) Arthropoda.
During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in ______________ signaling
(a) endocrine (b) paracrine (c) neuronal (d) contact-dependent