Question

A scientist studying the effects of radiation on DNA performs an experiment in which she exposes a sequence of nitrogen bases found in DNA to radiation. The DNA before and after the radiation is shown below.
Use the evidence to determine whether a mutation has occurred, and if so, interpret that mutation in the answer sheet provided

Before Exposure: ATCGTCA; After Exposure: ATTCGTCA

A. No mutation has occurred to the DNA sequence.

B. A nitrogen base has been deleted from the DNA molecule.

C. A nitrogen base has replaced another nitrogen base in the DNA molecule.

D. A nitrogen base has been added to the DNA molecule.

Answer 1

Answer:

D. A nitrogen base has been added to the DNA molecule.  

Explanation:

You can see that the sequence for the nitrogen bases are in the exact same order after the exposure, this rules out A.  You can count how many bases there are, 7 before and 8 after so it cannot be B. Lastly, given that they are in the same order as were before and that a base has been added, you can see that no bases were replaced (so not C) and that D is your answer.