In bilateral cases of retinoblastoma in a child, which of the following is usual
ID: 180263 • Letter: I
Question
In bilateral cases of retinoblastoma in a child, which of the following is usually assumed to have occurred? The child inherited a dominant RB mutation from one parent, and this led to retinoblastoma. The child inherited a mutation in a DNA repair gene from one parent that resulted in an increase in somatic mutations throughout the genome, including the RB gene. The child inherited a mutation in the RB gene from one parent and a mutation in the Myc oncogene from the other parent, and this combination of mutations resulted in retinoblastoma. The child inherited a RB mutation from one parent, and somatic mutations inactivated normal RB alleles in cell lines in each eye. The child inherited all normal alleles from the parents, but a somatic mutation in the p53 gene eventually gave rise to retinoblastoma. In bilateral cases of retinoblastoma in a child, which of the following is usually assumed to have occurred? The child inherited a dominant RB mutation from one parent, and this led to retinoblastoma. The child inherited a mutation in a DNA repair gene from one parent that resulted in an increase in somatic mutations throughout the genome, including the RB gene. The child inherited a mutation in the RB gene from one parent and a mutation in the Myc oncogene from the other parent, and this combination of mutations resulted in retinoblastoma. The child inherited a RB mutation from one parent, and somatic mutations inactivated normal RB alleles in cell lines in each eye. The child inherited all normal alleles from the parents, but a somatic mutation in the p53 gene eventually gave rise to retinoblastoma.Explanation / Answer
Bilateral retinoblastoma (BR) is an inheritable cancerous disease which causes formation of tumor in retina of both eyes in young individuals. The molecular mecahnism behind onset of BR has been described by two-hit model. According to this model, individuals with BR inherit one defected copy of retinoblastoma inducing oncogene from one of the parents. However, since a complementary healthy copy of the same gene is also present, they do not develop BR. However, sporadic mutation in the second healthy copy of the retinoblastoma allele might lead to generation of cancerous growth in both the retinas and thus develop bilaterial retinopathy. The oncogen Myc plays role in non-inheritable form of uniheritable form of retinoblastoma. Also, the oncogene p53 has not been shown to be clinically involved in pathogenesis of BR.
Thus, this description states that choice 4 is correct answer.
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