Chapter 19, Problem 18P

Summary Introduction

a.

To determine:

Whether the given proteins in the question act as a proto-oncogene or a tumor-suppressor gene.

Introduction:

The proto-oncogene is a normal gene that promotes cell growth. When a proto-oncogene undergoes a dominant mutation like a gain of function mutation, this gene becomes an oncogene. Tumor-Suppressor genes are normal genes that are responsible for inhibiting the cell proliferation and development of a tumor.

Summary Introduction

b.

To determine:

The effect of the addition of a phosphate group to the phosphatase by kinase A in the given problem.

Introduction:

Phosphatase enzymes are the enzymes responsible for removing phosphates from proteins.

Summary Introduction

c.

To determine:

Whether the phosphatase gene is likely to be a proto-oncogene or a tumor-suppressor gene or neither.

Introduction:

A normal proto-oncogene promotes cell proliferation. A normal tumor-suppressor gene inhibits cell proliferation.

Summary Introduction

d.

To determine:

Whether the listed mutations would lead to excessive cell growth or decreased cell growth if the cell were either homozygous for the mutation, or heterozygous for the mutation and a wild-type allele.

Introduction:

When a tumor suppressor gene undergoes loss of function mutation, it will result in cell proliferation. When a proto-oncogene undergoes gain of function mutation, it will cause cell proliferation. A null mutation makes a gene non-functional.