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Cancer Biology Exam 2 questions (updated & already graded A+)
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Cancer Biology Exam 2 questions (updated & already graded A+)
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Cancer Biology Exam 2questions 2025-
2026(updated & already
graded A+)
Sporadic cancer - answer No family history of the same
site specific cancer in a two generations
Hereditary cancer - answer o Family history of site specific
cancer (and related cancers)
o Follows Mendelian inheritance patterns
o High incidence and distribution
Knudson's Two Hit Hypothesis - answer o Two successive
mutations are needed to turn a normal cell into a tumor
cell
TSG's (Tumor Suppressor Genes) - answer o Act
DOMINATLY at GENETIC level via a mechanism that is
RECESSIVE at the CELLULAR (phenotypic) level.
Cell is normal phenotypically all the time it has at least
one functioning copy of the gene.
Once the second hit occurs, then the cell becomes
tumorigenic.
,Loss of the Second Copy - answer o Can happen due to the
exchange of material between non-sister chromatids
1.) Mitotic Nondisjunction - The chromatids don't split
correctly
2.) Mitotic recombination (Loss of heterogeneity)
3.) Gene Conversion - Transfer of bad information between
chromatids
Familial/Hereditary cancer caused by TSG's - answer
Retinoblastoma, Li-Fraumeni Syndrome, Colon Cancer
Promoter Methylation - answer o Causes transcriptional
inactivation
-Ex in Human Cancers: MGMT, p73
How to ID TSG's: 1 - answer o Cytogenetics or Comparative
genome hybridization
Useful to define tumor-specific deletions
Structural abnormalities, deletions (or insertions)
pinpoint potential tumor suppressor loci.
,How to ID TSG's: 2 - answer o Loss of Heterozygosity
studies in paired tumor and blood samples
Useful to identify small deletions at specific sites.
Molecular method of identifying deleted regions of DNA
(lots on c17/18 for p&q)
• Compare normal DNA vs tumor DNA
• Normally have to look at several regions
How to ID TSG's: 3 - answer o Linkage analysis:
STATISTICAL METHOD OF MAPPING A GENE
Useful to identify hereditary cancer in family pedigrees
Cosegregation of a DNA marker and tumor is strong
evidence for the site of the critical gene
Gene Mapping - answer o Follow the segregation of an
allele(s) for a certain gene during meiosis.
o Loci are Linked = Alleles transmitted together
The closer two loci are, the more likely they will
segregate together.
Theta (rF) - answer Recombination Frequency
, # of recombs / # total progeny
If it is less than 0.5, the genes may be linked
Move the decimal over two places to get the distance in
centiMorgans
Unlinked: # recombinants = # parentals
• 1:1:1:1 ratio, all numbers will the same.
Linked: # recombinants < # parentals (smaller # of
crossovers)
Closely linked: no recombinants; no crossovers
• You will only have the parental genotypes
LOD - answer • A relative value compared to if the loci are
NOT linked.
A ratio of theta (rF) to 0.5
Z - answer Maximum for a calculated range of theta. (Z =
highest LOD)
If you get a Z value between +3 and -2, it is linked
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