The widening of a tree trunk is mostly due to the activity of its
A. apical meristem.
B. secondary phloem.
C. vascular cambium.
D. primary xylem
Ans: C. vascular cambium.
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If the hypothesis stating viruses evolved prior to living organisms on Earth is true, the first type of viruses in the world were likely
A) bacteriophage. B) DNA viruses. C) retroviruses. D) RNA viruses.
Which one of the following is not a cell surface-type receptor?
A. G protein-coupled receptor B. steroid receptor C. ligand-gated receptor D. receptor kinase
A scientist reports the isolation of a new blood-borne virus that completely shuts down presentation of viral epitopes on MHC molecules in the cells it infects
He produces an internet video describing it and how it will be indestructible by CD8+ cytotoxic T cells and will kill millions (if not billions) of people.The medical community quickly denounces the dire warning as irrevlevant, and the whole thing is quickly forgotten-why? A. CD8+ T cells are not the cells that are responsible for killing virally infected cells. The terrorist mad scientist is a misinformed idiot. B. While CD8+ T cells ARE important for eliminating a viral infection, they are not the ONLY things that are capable of doing so. Natural killer cells can kill virally infected cells that have shut down MHC antigen presentation, and interferons can assist in cleaning virally infected cells. C. A blood-borne virus would not be capable of rapidly infecting millions of people, due to its difficult mode of transmission. D. B cells would be primed right away to produce complement proteins to destroy the virus. This would prevent cells from being infected with it in the first place. His plot would be foiled. E. While CD8+ T cells ARE important for eliminating a viral infection, they are not the ONLY things that are capable of doing so. Natural killer cells can kill virally infected cells that have shut down MHC antigen presentation, and interferons can assist in cleaning virally infected cells AND a blood-borne virus would not be capable of rapidly infecting millions of people, due to its difficult mode of transmission.
Cushing's syndrome causes weight gain, excessive sweating, and muscle weakness. It can result from either the production of abnormally high levels of cortisol by the body or overuse of glucocorticosteroid drugs. You are an endocrinologist working with a Cushing's syndrome patient. She is on hormonal birth control pills and takes an occasional ibuprofen.Results from lab tests reveal abnormally high endogenous hormone levels, and you suspect a possible tumor. What regions will you ask the MRI technician to focus on?
A. Hypothalamus and posterior pituitary B. Adrenal cortex only C. Anterior and posterior pituitary D. Hypothalamus, anterior pituitary, and adrenal cortex