Final answer:
Gene family evolution, such as seen in alpha- and beta-hemoglobins and conotoxins, can occur through gene duplication events followed by divergence and adaptation. The duplicated genes accumulate mutations and changes that lead to different functions.
Step-by-step explanation:
The phenomenon you're referring to, in which nucleotide sequences between different species in a gene family appear to be more similar than those within the same species, is known as gene family evolution. This can happen due to a process called gene duplication, which occurs when a gene is copied to create an additional version. Over time, these duplicated genes can undergo mutations and accumulate changes that lead to different functions.
For example, let's consider the alpha- and beta-hemoglobin genes. These genes are part of a gene family involved in oxygen transport. In humans, there are multiple versions of each gene known as alpha-hemoglobin genes and beta-hemoglobin genes. The sequence similarity between the alpha-hemoglobin genes in humans and those in other species, like primates, is higher compared to the sequence similarity between different alpha-hemoglobin genes within humans. The same is true for beta-hemoglobin genes. This suggests that gene duplication followed by divergence and adaptation has occurred over evolutionary time.
In the case of conotoxins, which are a family of venom peptides produced by cone snails, the nucleotide sequences between different species are also more similar than the sequences within the same species. Cone snails have evolved to produce diverse conotoxins with varying functions, such as paralyzing or killing their prey. Gene duplication events have generated multiple copies of conotoxin genes within the genome of cone snails. Each copy can then accumulate unique mutations, leading to different conotoxins with distinct target proteins and modes of action.