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genetics question - - Printable Version +- USMLE Forum - Largest USMLE Community (https://www.usmleforum.com) +-- Forum: USMLE Forum (https://www.usmleforum.com/forumdisplay.php?fid=1) +--- Forum: Step 1 (https://www.usmleforum.com/forumdisplay.php?fid=2) +--- Thread: genetics question - (/showthread.php?tid=20112) |
genetics question - - ArchivalUser - 08-19-2004 sebastian dude comes in that has had no retinoblastomas (Rb), but has produced 2 kids w/ multiple Rbs. His dad also had 2 Rbs and one of his brothers has 3 Rbs. Which of the following is the most likely explanation for the abscence of the retinoblastoma in this individual? -pleiotropy - 0 - ArchivalUser - 08-19-2004 mash incomplete penetrance 0 - ArchivalUser - 08-19-2004 sebastian sorry, accidently clicked submit.... remaining 4 choices: -highly variable expression of the disorder -incomplete penetrance -multiple new mutations in other family members -a new mutation in the unaffected individual, which has corrected the disease-causing mutation 0 - ArchivalUser - 08-19-2004 sebastian damn Mash!!!!! 0 - ArchivalUser - 08-19-2004 sebastian one question though, Mash....if you need 2 mutations for expression of the tumor, isnt it more of a case of the guy not having suffered that 2nd mutation (while his family members have)?!? I thought imcomplete penetrance was more of having ALL the mutations necessary for the phenotypic alteration....but simply not expression it. You get what i mean?!? 0 - ArchivalUser - 08-19-2004 sebastian as defined in 1st aid...he doesn't possess the required "2" mutations needed for altered expression, correct?!? 0 - ArchivalUser - 08-19-2004 mash u r right but retinoblastoma is AD and as such just one mutant allele is reqd ...bcoz it is a tm suppressor gene, 2nd hit is reqd to express the ds. incomplete penetrance is when the person inherits the mutant allele and he shud express it but he doesn't ideally he shud ve had retinoblastoma bcoz he transmitted the mutant allele to his sons(rb being AD) 0 - ArchivalUser - 08-19-2004 sebastian Gotcha.....Thanks Mash for your help!! |