Which characteristics are shared by birds and mammals?
they have a three-chambered heart and are endothermic.
they typically give birth to live young and fertilize internally.
they reproduce sexually and typically give birth to live young.
they are endothermic and reproduce sexually.

You are studying a protein that you call protein x. there is an aspartic acid at a key position in protein x which is important in the folding and stabilization of that protein. if this aspartic acid is changed to a different amino acid, which type of amino acid substitutions is most likely to allow the protein to fold normally?