Question

A gene called c-ABL, which codes for nTRK in B-cells, is translocated from chromosome 9 to chromosome 22. In chromosome 22 it is integrated into a gene called BCR. This translocation causes chromosome 22 to be defective and short, and contains a sort of "hybrid" BCR/ABL gene. The hybrid gene produces hybrid proteins with an nRTK attached to it which is always active and leads to unregulated cell division?

Answer 1

Translocation between chromosomes 9 and 22 results in a hybrid BCR-ABL gene that causes chronic myelogenous leukemia due to continuous activation of tyrosine kinase leading to unregulated cell growth.

Step-by-step explanation:

The translocation of the c-ABL gene on chromosome 9 to chromosome 22, where it fuses with the BCR gene, creates a hybrid BCR-ABL gene. This gene codes for a constitutively active tyrosine kinase, which is always 'on' and causes unregulated cell division, leading to diseases such as chronic myelogenous leukemia (CML). Large scale mutations, like the creation of the Philadelphia chromosome through translocation, can result in the activation of proto-oncogenes into oncogenes, leading to cancer.

Reciprocal translocations, which involve the exchange of segments between nonhomologous chromosomes without loss or gain of genetic material, can still have serious consequences if they alter gene positioning with respect to regulatory sequences, as seen in CML. Overexpression or unregulated activity of such oncogenes can transform normal cells into cancerous ones, leading to unchecked growth and potential tumor formation.