Biologists now routinely test for homology between genes in different species. if genes are determined to be homologous, it means that they are related

The answer is ‘by descent from a common ancestor’. Sequence homology (nucleotide or amino acid sequence similarity) is used  to compare two segments of DNA for shared ancestry through either of the following three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs).

what subject is this

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation: