Question

Three species of lizard, labeled A, B, and C, are being studied using molecular analysis by two research colleagues in different laboratories. The mitochondrial DNA of lizards A and B are compared and are found to differ by 0.1%. The ribosomal RNA of lizards B and C are found to differ by 0.02%. They compare their findings and conclude that lizard B is more closely related to C than to A. What is the flaw in their reasoning, and how can their analysis be improved?
A. They applied different mathematical formulas for their computations. They should recalculate using the same formulas.
B. They compared different molecules which have different mutation rates. They should compare same molecule in the lizards.
C. They only made one measurement each. They should repeat their measurements to reduce the uncertainty in their results.
D. They used different equipment for analyzing the molecules since they work in different labs. They should work in the same lab.

Answer 1

Answer:

The most appropriate answer would be option B.

The flaw in their reasoning is that they compared different molecules in a different set of organisms.  

For example, they compared the DNA of lizard A and B whereas they compared the RNA of lizard B and C.

In addition, the mutation rates of different molecules (DNA and RNA) are different and thus, comparison of DNA in one set of organism and comparison of RNA in another set cannot be used as the basis for the conclusion.

Answer 2

Answer:

B. They compared different molecules which have different mutation rates. They should compare same molecule in the lizards.

Explanation:

The researchers shown in the question above wish to discover the genetic relationship of three lizards based on analyzes of different molecules. The researchers evaluated the difference between DNA in lizards A and B and evaluated the difference between RNA molecules between lizards B and C, so it is not possible to detect a genetic relationship between lizards. The correct thing would be for researchers to investigate only the DNA of all lizards, or just the RNA of all lizards.