Chromosomes contain genes, regulatory sequences, and non-coding sequences. in prokaryotes, most dna is made up of genes or regulatory sequences. however, eukaryotes have a large amount of dna that does not code for proteins and is not part of regulatory sequences. for example, only about 1.5% or less of human dna is coding dna. as a result, eukaryotic genomes are often much larger than would be expected from the number of genes.
which of the following are noncoding dna that contribute to the large size of eukaryotic genomes? select all that apply.

a. alu elements
b. gene duplications
c. multiple variants of a gene
d. exons
e. repetitive sequences (simple sequence repeats)