If a mutation prevents the formation of lignin, which
tissue will be most affected?
a. vascular cambium
b. parenchyma
c. collenchyma
d. sclerenchyma
e. all of these
Answer: d
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This tissue gives pear flesh a gritty texture and makes seed coats hard:
a. xylem b. collenchyma c. phloem d. sclerenchyma e. parenchyma
A neuron subjected to a strong stimulus responds by increasing the _______ of its action potentials.
A. frequency B. size C. speed D. two of the above
APC is a tumor suppressor and acts in the Wnt signaling pathway to prevent the TCF complex from turning on Wnt-responsive genes
Mice that lack the gene encoding TCF4 do not have the ability to maintain the pool of proliferating gut stem cells needed to renew the gut lining. What do you predict will happen in mice that lack the APC gene? (a) Mice lacking the APC gene will be like the mice lacking TCF4 and not be able to renew the gut lining. (b) Mice lacking the APC gene will have inappropriate proliferation of gut stem cells. (c) Mice lacking the APC gene will have a hyperactive Wnt receptor even though there is no Wnt signal. (d) Mice lacking the APC gene will be like normal healthy mice, since APC is a tumor suppressor and thus not needed unless there is a tumor present.
Mechanical digestion in the human digestive system is best illustrated by ____
a. absorption b. amylase c. bacterial action in the large intestine d. chewing e. pepsin