In the familial form of retinoblastoma, individuals who inherit one mutant allele of the RB1 gene have an 85% chance
of developing retinoblastoma and other cancers. Explain why, when these individuals carry only one copy of the mutant
gene, there is such a high incidence of cancer in these RB1 heterozygotes. What will be an ideal response?
ANSWER: Those who inherit the mutant allele carry it in all of their somatic cells, and loss of
heterozygosity by mutation of the normal allele anywhere in the body can result in cancer.
Since there are approximately 1013 cells in the body, chances are very high that a mutat will occur in at least one cell in the normal allele at some point during an individual’s life and
lead to cancer.
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Diatoms
A. can reproduce asexually. B. are photosynthetic with frustules composed of two halves. C. are motile by virtue of having flagella. D. are photosynthetic with frustules composed of two halves and can reproduce asexually.
The Hubbard Brook Watershed Project illustrated that ____
a. deforestation increases nutrients in nearby aquatic ecosystems b. deforestation can result in polluted streams c. deforestation results in calcium retention in soil d. primary consumers are the most important part of that energy pyramid e. trees absorb too much water and are not useful in a watershed area
A hypothesis is a(n) ________
A) tentative answer to a question B) guess C) observation D) theory
Birds and fishes overcome gravitational forces primarily through their ________.
A. body shape and density B. lubricating secretions C. smooth outer covering D. textured surface E. reduced surface area in contact with the ground