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this thread with ur help will be devoted to those having misunderstandings and weak score in behavioral sciences and genetics in their NBMEs and other self assesment so it is gonna be like a group treatment
every interesting thing and relevant u know post it every question u have post it
guess this specially the case for iMGs cuz no much focus on those topics in our medical school
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Loss of heterozygosity is when u r heterozygous for a phenotype and then after a mutation or deletion u become homzygous ( u loose this heterozygosity ).
if it is with regard to an AR disease then the phenotype will appear
do u know some else relevant in this topic
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can you drop your email here drfuture .I have something to give you for biostatistics.
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Loss of heterozygosity (LOH):
At a particular locus heterozygous for a deleterious (harmful/lethal) mutant allele and a normal allele, a deletion or other mutational event within the normal allele renders the cell either hemizygous (one deleterious allele and one deleted allele) or homozygous for the deleterious allele.
LOH of chromosomal regions bearing tumor suppressors is a key event in the evolution of tumors and cancer.
There are several mechanisms which can cause a cell to lose its normal gene and thus be predisposed to develop into a tumor. These may result in "LOH".
Mechanisms of LOH:
1. Deletion of
a. the normal allele;
b. the chromosome arm containing the normal allele;
c. the entire chromosome containing the normal allele (resulting in aneuploidy).
2. In females, X-inactivation of the X chromosome carrying the normal allele.
3. Loss of the chromosome containing the normal allele followed by duplication of the chromosome containing the mutated allele.
4. Mitotic recombination. The study of tumor suppressor genes revealed (for the first time) that crossing over — with genetic recombination — occasionally occurs in mitosis (as it always does in meiosis).
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thanks
point 2 is interesting:
when a female patient develops an xlinked disease it is called manifest heterozygote cuz it happens that the random inactivation of the x chromosomes in her cell happened to inactivate the normal x chromosomes instead of the mutated x chromosomes
so can we say that the Term MANIFEST HETEROZYGOTE is in some way loss of heterozygosity /?/
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Lac operon question:
if we put an Ecoli in a medium with both glucose and lactose will it be able to take in and brake lactose???? explanation please
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adenylate cyclase ... cAMP ... cAMP CAP protein which will bind promotor region and stimulate operon expression of lactose braking enzymes
But when we put glucsose it inhibits adenylate cyclase ( dont know why and how) and there is decreased brake down of lactose
if also lactose is present it will inhibit the repressor protein ( a protein that binds and inhibits the operator region) so there will be stimulation of operator production of enzymes that brake down the lactose
so two opposing steps which one will have the major effect??????????????????????????????????????
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hey some contribution here please do not underestimate those two subjects
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i think lactose presence is the major effect!