Final answer:
Regions of DNA that are highly variable are used to identify different species, as they allow differentiation between species and contain conserved sequences for comparison. Methods like DNA or RNA sequence alignment are used to find similarities and understand evolutionary relationships. option b is correct.
Step-by-step explanation:
To identify different species, regions of DNA that are highly variable are used. These regions are chosen because they include sufficient variability to differentiate between species while also having enough conserved sequences to allow for alignment and comparison. Highly conserved regions tend to show similarity across various species, reflecting evolutionary relationships, but may not have enough variation to distinguish closely related species.
On the other hand, poorly conserved regions might evolve too quickly, compromising the ability to identify longer-term evolutionary relationships. Therefore, moderately variable regions, such as mitochondrial DNA in animals and chloroplast DNA in plants (except in the case of eukaryotes with the exception of plants where mitochondrial genes are more useful), are commonly used for species identification and for DNA barcoding, which relies upon the rate of evolution of the chosen gene.
When constructing individual genetic maps, it is understood that they are generally genetically similar but not identical within a species due to individual genetic variations. To identify regions of similarity between cell types or species, the technique of DNA or RNA sequence alignment is employed rather than sequencing methods like dideoxy chain termination or whole-exome sequencing. Such alignments can reveal evolutionary relationships by comparing sequences across different species.