Which of the following is a physical barrier for the nonspecific defense mechanism?
a) Fever
b) Hair
c) Inflammation
d) Stomach acid
Ans: a) Fever
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Communication between cells always involves four components, including a signaling cell, a signaling molecule, a receptor, and a target responding cell. Mark each of the following statements about cell communication true or false
____ Signaling molecules are always secreted from the signaling cell. ____ The distance travelled by the signaling molecule to the responding cell varies tremendously depending on the signal. ____ A specific signaling molecule may bind to receptors on more than one kind of cell. ____ Receptors for signaling molecules are always integral membrane proteins on the surface of responding cells. ____ Signaling molecules involved in endocrine signaling are always hydrophobic hormones like testosterone. ____ Peptide signaling molecules are only involved in paracrine or autocrine signaling. What will be an ideal response?
With few exceptions, we can't use observable traits to measure genetic variation in populations because:
A. observable traits don't vary enough among individuals to measure. B. we can't identify enough observable traits to be useful, even if they could be measured. C. many traits are encoded by large numbers of genes. D. observable traits are products of the environment as well as the genome. E. Many traits are encoded by large numbers of genes, and observable traits are products of the environment as well as the genome.
DNA replication can stall as a consequence of the replication machinery encountering hairpin DNA structures that can form due to inverted repeats and palindromic sequences
When DNA replication stalls, double-strand breaks in the DNA can occur, causing severe genetic and cellular consequences. Both Werner syndrome (premature onset of age-related phenotypes and cancer) and Bloom syndrome (cancer) are the result of mutations in helicase, an enzyme that unwinds hairpin structures. Helicase most likely breaks which type of bonds in a hairpin? A. glycosidic B. phosphodiester C. hydrogen D. peptide E. covalent
Carpal tunnel syndrome is caused by an inflammation of tendons passing through the carpal tunnel of the wrist. What causes this inflammation and pain?
A) The associated muscles are too weak and begin to spasm, leading to inflammation. B) The muscles eventually fatigue and become swollen, thus swelling the tendon. C) The tendons become stretched out and ultimately tear away from the bone. D) Certain continuous hand motions cause the tendons to repeatedly rub against bone.