Question

Retinoblastoma (Rb) is the model genetic system for tumor suppressor genes. Analysis of DNA from retinoblastoma patients revealed that Rb is a recessive autosomal condition with LOH; however, analysis of pedigrees segregating for the familial form of Rb indicates that the condition is inherited as an autosomal dominant trait. Explain the apparent inconsistency and define LOH.

Answer 1

Retinoblastoma (Rb) -Retinoblastoma is an eye cancer that begins in the retina — the sensitive lining on the inside of the eye. Retinoblastoma most commonly affects young children, but can rarely occur in adults. Retinoblastoma is a protein that involves in cell cycle and acts as a cell cycle inhibitor the mutation in this protein gene will cause a tumor.

Rb is inherited as a recessive autosomal way. if one of the 2 genes is defective then the individual is normal but both genes are mutated then the retinoblastoma will be seen.  

The reason behind this is that the person who is carrying this mutated gene has a high chance of having cancer around 90 percent chances. if the LOH  that is the loss of heterozygosity happened that means if the somatic cells got mutated for the normal Rb gene it will form a homozygous condition and this cancer will be developed in that individual

Now, Loss of heterozygosity that means the cell changes into a homozygous form for that particular gene. it happens by mutation for example if the cell is having one normal and one affected gene then by a mutation that normal gene changes into affected gene now cell has 2 abnormal genes it is called loss of heterozygosity