MRNA (messenger RNA) is produced during the process of transcription. During transcription, the sequence of DNA is transcribed into mRNA. Later, during translation, mRNA sequence is translated into a protein molecule. So, if a cell were unable to make mRNA (probably after transcription failure), that mRNA would not be translated into protein. Without the protein, the cell's function or structure would be disrupted.
Explanation: The random change in the gene pool is due to genetic drift. Remember, genetic drift occurs at a more rapid rate when the population size is reduced. The flood is a random occurrence. It could have as easily been a drought.
