Telomeres with repetitive DNA sequences

The ends of a linear chromosome are not readily replicated by cellular DNA polymerases. As we know that DNA polymerases requires a template and primer, and beyond the end of a linear DNA molecule no template is available for the pairing of an RNA primer. This may cause shortening of chromosomes during each replication cycle due to loss of its terminal. Telomeres are the structures present at the ends of linear eukaryotic chromosomes and have many tandem copies of a short oligonucleotide sequence. This sequence has mostly guanine residues in one strand and cytosine in the complementary strand. The G-rich strand is longer leaving a region of single-stranded DNA of up to a few hundred nucleotides at the 3’ end which serves as the primer for its elongation by telomerase enzyme. Replicon is the unit of DNA that carries a replication origin site and a termination site and is able of self-replication. Transcription factors TFIIA (Stabilizes binding of TFIIB and TBP to the promoter), TFIIB (Binds to TBP; recruits Pol II–TFIIF complex), TFIIE (helicase activities) and TFIIF (prevents binding of Pol II to nonspecific DNA sequences) serve as transcription initiators. Synaptonemal complex is a proteinaceous structure that appears between the homologous chromosomes and mediates synapsis. The correct answer is D.