MCDB XL 100 CHAPTER 20 EXAM 2024/2025 WITH 100% ACCURATE SOLUTIONS
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Chondroma - Precise Answer A benign neoplasia of cartilage is called a:
Chondrosarcoma - Precise Answer A malignant neoplasia of cartilage is called a:
Among the following cancers, one is currently leading to the most number of deaths in the United States and in the rest of the world. In the ...
MCDB XL 100 CHAPTER 20 EXAM
2024/2025 WITH 100% ACCURATE
SOLUTIONS
Chondroma - Precise Answer ✔✔A benign neoplasia of cartilage is called a:
Chondrosarcoma - Precise Answer ✔✔A malignant neoplasia of cartilage is called
a:
Among the following cancers, one is currently leading to the most number of
deaths in the United States and in the rest of the world. In the United States, it
contributes to cancer mortality more than the next three killing cancers combined.
Worldwide, it claims more than 1.5 million lives every year. Which cancer is this?
A. Lung cancer
B. Breast cancer
C. Colon cancer
D. Pancreatic cancer
E. Stomach cancer - Precise Answer ✔✔A
In medical oncology, PET (positron emission tomography) is used to selectively
image
tumors in the body and to monitor cancer progression and response to treatment.
Before
performing a PET scan, the patient should fast for at least several hours for blood
glucose to be sufficiently low. At the time of the scan, the positron-emitting
glucose analog
,fluorodeoxyglucose (FDG) is injected into the bloodstream and the patient is asked
to wait for up to an hour while avoiding physical activity. Finally, the scanner
moves slowly over the body to reveal the location of possible tumors. Why do you
think the patient should avoid physical activity before the scan? - Precise Answer
✔✔To prevent the absorption of the radioactive tracer by healthy tissues.
When the blood glucose level is low, the added radioactive glucose analog is
preferentially and rapidly taken up by tumor cells as a result of the Warburg effect.
Physical activity stimulates uptake by muscle cells also (including heart muscle),
which interferes with the imaging.
Mutations in two important cancer-critical genes, encoding p53 and Rb,
respectively, are
commonly found in cancers. What type of mutations are these expected to be? -
Precise Answer ✔✔Loss-of-function mutations in both genes
Both p53 and Rb are coded by tumor suppressor genes, and their inactivation
promotes cancer.
The homologous chromosome pairs in our cells do not carry identical sequences in
all
loci. This heterozygosity (difference between the two copies) can be altered in
cancer: in fact,
loss of heterozygosity at many loci is observed in cancer cells, through an increase
in either
homozygosity (two identical copies) or hemizygosity (i.e. loss of one copy).
Researchers can take advantage of this loss of heterozygosity in cancer cells to
identify genomic loci that contain cancer-critical genes. What type of gene would
you expect to find in chromosomal regions with a loss of heterozygosity? Proto-
oncogenes (P) or tumor suppressor genes (T)? - Precise Answer ✔✔T
, Once the first copy of a tumor suppressor gene is lost or inactivated, the remaining
copy is commonly lost by a less specific mechanism, leading to loss of
heterozygosity in the gene as well as in its neighboring loci. This represents a way
of finding loci that contain tumor suppressor genes.
The immortalized non-malignant mouse cell line NIH-3T3 was derived from
normal
mouse fibroblasts in the early 1960s. These cells are able to readily take up
exogenous DNA and are prone to transformation by cancer-causing agents,
including some retroviruses. DNA extracted from a human bladder carcinoma line
is able to transform these cells, as judged by a significant increase in the number of
foci (cell clumps) in the cell-culture plates when the DNA is added. The malignant
cells contain human DNA, and the DNA can be shown by sequence analysis to
contain a single mutant gene that is present in the original bladder carcinoma cell
line. The gene codes for a monomeric G protein and was one of the first cancer-
critical genes to
be identified in this way. The protein encoded by this gene is: - Precise Answer
✔✔Ras
Ras was also found earlier to be the oncogene carried by some sarcoma viruses,
and the identification of the same gene (with similar mutations) in both cases was
an important discovery that advanced our understanding of the molecular biology
of cancer.
Retinoblastoma is an early-onset cancer of the retina with a rapid progression, and
is
mostly diagnosed in children. In its hereditary form, multiple eye tumors usually
arise in both
eyes, while the nonhereditary form usually causes fewer tumors in only one eye.
Treatment may
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