Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

Which statement best defines a mutation?

1. A change in the morphology of an organism

2. A type of genetic variation passed from parents to offspring

3. A change in the DNA of a cell that can be beneficial

4. An error in the replication of RNA only

The correct answer is: A change in the DNA of a cell that can be beneficial

The statement that a mutation is a change in the DNA of a cell that can be beneficial captures the essence of what mutations are and their potential impact. Mutations refer to alterations in the nucleotide sequence of an organism's DNA, which can occur due to various factors including environmental influences, replication errors, or exposure to certain chemicals. While not all mutations are beneficial, many can provide the raw material for evolution by introducing genetic variation. Beneficial mutations may increase an organism's fitness, allowing it to adapt more effectively to its environment. Examining the other statements, a change in the morphology of an organism refers to physical traits, which is not necessarily a direct reflection of mutations alone as morphology can also be influenced by environmental factors and complex genetics. Genetic variation passed from parents to offspring is typically achieved through established genetic processes like inheritance rather than mutations alone. Lastly, an error in the replication of RNA only suggests a limitation that does not encompass the broader nature of mutations that primarily involve DNA changes. Thus, mutation encompasses a wider range of changes, including those that can enhance survival and adaptation in dynamic ecosystems.