The one-bit deletion and duplication channel is investigated. An input to this channel consists of a block of bits which experiences either a deletion, or a duplication, or remains unchanged. For this channel a capacity expression is obtained in a certain asymptotic regime where the deletion and duplication probabilities tend to zero. As a corollary, we obtain an asymptotic expression for the capacity of the segmented deletion and duplication channel where the input now consists of several blocks and each block independently experiences either a deletion, or a duplication, or remains unchanged.