Final answer:
In the given options, introns and promoters are referred to as 'non-coding' DNA because they do not encode for proteins.
Step-by-step explanation:
In eukaryotic genomes, not all DNA sequences code for proteins. Among the options provided, the non-coding DNA sequences are introns, which are segments that do not encode protein and are typically removed from the mRNA before it is translated into protein, and promoters, which are sequences of DNA that initiate transcription for a particular gene. Although exons do include coding sequences, they are flanked by introns, which are non-coding. Additionally, while codons are specific sequences of three nucleotides that correspond to amino acids or stop signals during translation, they are part of the coding sequence and so are not considered non-coding DNA.
The correct non-coding elements in the provided options are therefore (a) introns and (c) promoters as they do not encode proteins, unlike exons and codons which are part of the coding region of a gene.
sequences within genes that are transcribed into mRNA but are removed before translation, while promoters are specific sequences of DNA nucleotides that signal the start of gene transcription. On the other hand, exons and codons are not non-coding DNA.