11. About genetic mutation, which of the following statement is TRUE? (A) Silent mutations usually do not have observable effects on phenotypes because they are in-frame mutations (B) Missense mutations change a codon into a stop codon leading to a truncated protein (C) Nonsense mutation is a point mutation in which a single nucleotide change resulted in a change in an amino acid (D) Insertions and deletions are additions or losses of nucleotides in a gene that usually alter the reading frame producing frame-shifted mutations

13. The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data? (A) Forelimb evolution was adaptive in people and bats, but not in whales (B) Whales are not properly classified as mammals (C) Genes mutate faster in whales than in humans or bats (D) Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy

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