Note that while many amino acids match between rat and human, many nucleotides do NOT match. Also notice the pairs of nucleotides found at the start and end of the long unmatched region. What do you think this region represents

allowed for the prediction of the properties of missing elements.

the right option is; decreased genetic variation  

decreased genetic variation describes the effect of this environmental change.

genetic variation is the naturally occurring genetic diversities or differences between organisms of the same species in a population. genetic variation allows the survival and adaptability of a species when they encounter changing environmental conditions. when an endangered species reduces, it loses genetic variation which may not be restored even if the species rebound and will only be recovered through the gradual collection of mutations over many years.