Using breast cancer as an example, describe the importance of understanding the interactions of an individual’s
genotype with therapeutic drugs when treating patients What will be an ideal response?
ANSWER: About 75% of all breast cancers are estrogen positive. This means that cells from these
cancers carry estrogen receptors on their surfaces and that estrogen in the body helps promote
the growth of these cancers. One of the drugs widely used to treat estrogen-sensitive breast
cancer is tamoxifen. Once in the body, tamoxifen is converted into endoxifen, a powerful
anti-estrogen drug. Tamoxifen is converted into endoxifen by a specific enzyme and four
distinct phenotypic groups are recognized. One group converts tamoxifen to endoxifen very
slowly and has low levels of the active drug in the body. Another group has an intermediate
rate of conversion of tamoxifen to endoxifen. Members of a third group are classed as
extensive metabolizers of tamoxifen, and those in the fourth group are ultrarapid
metabolizers. Alleles that abolish or decrease the enzyme activity lead to significantly
reduced blood levels of endoxifen. Clinical evaluation of breast cancer recurrence and
genotypes with the specific enzyme indicates that women with the poorest conversion rate
have a twofold to threefold higher risk of recurrence than women with higher metabolic rates.
This research clearly demonstrates that genotype should be considered as an important factor
in selecting drugs and dose rates for breast cancer treatment.
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Why are the ends of microfilaments and microtubules called "plus ends" and "minus ends"?
A. because monomers are added more quickly to one end (the "plus end") than they are to the other end (the "minus end") B. because polymerization occurs at one end (the "plus end") and depolymerization occurs at the other end (the "minus end") C. because monomers can be added to one end only (the "plus end"), and can only be removed from the other end (the "minus end") D. because the actin and tubulin monomers that make up microfilaments and microtubules have evolved more rapidly than most other proteins
Terns, skuas and jaegers are all related to the ____ group
a. gull b. pelican c. tubenose d. penguin e. shorebird
Are constructed of all four basic tissue types
a. Organs. b. Systems. c. Cells. d. Organelles.
Which statement about whisk ferns is FALSE?
a. They exhibit dichotomous branching. b. One representative is Psilotum. c. They lack true leaves. d. They lack true roots. e. They lack true stems.