Answer:
A mutation that causes a single letter change in the DNA sequence can affect your protein structure and function because the sequence of letters in a gene determines the sequence of amino acids in the protein that it encodes. A single letter change in the DNA alters the mRNA which alters the amino acid sequence of the resulting protein and sometimes that can cause serious results if it changes the way a protein works.
ex. sickle cell disease - a single letter swap in the gene that encodes the hemoglobin molecule results in deformed red blood cells
Hope that helps.
C. Helpful variations accumulate among surviving members of a species
Transcription is the transfer of genetic information from DNA to RNA, and it happens in the nucleus. We can automatically rule out B. B is incorrect because it doesn't make sense; how can a process stop before it even begins?
A. I believe this is incorrect because mRNA is involved when the genetic information needs to leave the nucleus. mRNA would take it to a ribosome outside of a nucleus. Since transcription happens in the nucleus, mRNA is irrelevant before it starts.
C. This doesn't really make sense. mRNA carries information from the DNA, but not vice versa (in these early stages).
D. This would make the most sense, since RNA polymerase needs to attach to the promoter on the strand before transcription can begin.
All of the above points are valid for fossils' contributions in understanding the process of evolution. They allow us to study the ancestry, we can see the homologous organs or structures, if fossils are well-preserved; different fossils can lead us to follow the cycles of the changes that occurred during macroevolutions, and fossils can be used to study different populations which had different body structures for surviving in different environmental conditions.
