Final answer:
All of the listed options (Centromeres, Alu elements, LINE elements, and Telomeres) are composed of repetitive DNA elements. These elements play crucial roles in the structure, function, and evolution of the eukaryotic genome, and are not considered 'junk DNA'.
Step-by-step explanation:
Repetitive DNA elements are fundamental components of the eukaryotic genome structure and can be found in various places within the DNA. The correct answer to the question about which of the following are composed of repetitive DNA elements is E: All of the above. This includes:
- Centromeres: which are essential for the segregation of chromosomes during cell division and consist of repetitive DNA sequences.
- Alu elements: which are short stretches of DNA that can copy and insert themselves at new locations within the genome. They are a type of SINE (Short Interspersed Nuclear Element) and are very abundant in the human genome.
- LINE elements (Long Interspersed Nuclear Elements): which are another type of transposable DNA and account for a significant portion of the genome.
- Telomeres: which are the protective caps at the tips of chromosomes composed of repetitive nucleotide sequences. They protect the coding sequences during the process of DNA replication.
The observation of a significant portion of a eukaryotic genome being made up of repetitive DNA, including transposons which can reach up to 80% in some cases, refutes the outdated concept of 'junk DNA' and highlights the key roles these elements play in gene regulation, genome reshaping, and increasing genetic diversity in evolution.