phuluong2k
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42 yo woman, mentions that her brother 48 yO recently diagnosed with colon cancer. A maternal uncle is ded of colorectal cancer at age 50. The doctor suspects familial polyposis. But the brother medical record showsno evidence of this, mutation testing on brother show MLH1 mutation.
What characteristic associated with mutation is likely to be noted in the tumor cell DNA from her brother.
A. Active transcription of telomerase
B. Increase in euchromatin
C. Highly methylated CG sequence
D. Large fragment deletion
E. Dinucleotide repeat instability
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| mjl1717
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My guess is d, since in deletion their is usually profound loss of function.
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| SDK
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I agree with mjl1717.
Mutation of MLH1 or MLH2-----defective repair of DNA mismatch.
this may due to large fragment deletion??
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| phuluong2k
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E is right, he got hereditary nonpolyposis cancer
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| Frida
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HNPCC
Microsatelite instablity in the tumor cells goes with patients with loss of fxn mutation in the mismatch pair genes (hMLH, hMSH) associated with HNPCC and hereditary endometrial cancer. Areas of DNA with dinucleotide repeats (i.e.microsatellites) are often assoc. with strand slippage durand DNA replication that can change the number of repeats on the newly synthesized strand (microsattelite inestability). The mismatch repair enzymes normally correct this replication error.
Large segment delitions are assoc. with unequal crossovers during meiosis. A large segment delition might result in a deficiency or loss of a tumor suppressor gene and a hereditary form of cancer. The mechanism is not assoc. with a mismatch repair.
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| SDK
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Nice explanation-----thnx 
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