A few decades ago, Knudsen and colleagues proposed a theory that, for a normal cell to become a cancer cell, a minimum of two genetic changes had to occur in that cell. Knudsen was studying retinoblastoma, a childhood cancer of the eye.
-One of the human leukemias, called CML (chronic myelogenous leukemia), is associated with a chromosomal translocation between chromosomes 9 and 22 in somatic cells of bone marrow. Which of the following allows CML to provide further evidence of this multistep nature of cancer?
A) CML usually occurs in more elderly persons (late age of onset).
B) The resulting chromosome 22 is abnormally short; it is then known as the Philadelphia chromosome.
C) The translocation requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces.
D) CML involves a proto-oncogene known as abl.
E) CML can usually be treated by chemotherapy.

Question

Quizplus · Accepted Answer

The fact that the translocation in CML requires breaks in both chromosomes 9 and 22, followed by fusion between the reciprocal pieces, suggests that it is a multistep process involving multiple genetic changes, providing further evidence for the Knudsen's theory that multiple genetic changes are necessary for normal cells to become cancerous. The other choices do not address the multistep nature of cancer.

A Few Decades Ago, Knudsen and Colleagues Proposed a Theory