Final answer:
The statement that DNA molecules have short RNA primers that are replaced with DNA nucleotides is true. DNA replication requires RNA primers for DNA polymerases to begin synthesis, which are later removed and substituted with DNA nucleotides, and the entire strand is sealed by DNA ligase.
Step-by-step explanation:
The statement that all DNA molecules initially have short RNA primers embedded within them, which are later removed and replaced with DNA nucleotides, is True. During DNA replication, short RNA primers are synthesized by an enzyme called primase, and these primers are necessary for DNA polymerases to initiate the synthesis of the DNA strand. This occurs because DNA polymerases can only add nucleotides to an existing strand of nucleic acid, and they cannot start the synthesis de novo. After the DNA strand has been extended, the RNA primers are removed by exonuclease activity, and the gaps that are left behind are filled with DNA nucleotides by a different DNA polymerase. The final step in this process involves DNA ligase, which seals the DNA fragments, creating a continuous DNA strand.
To address the additional true/false questions provided for context:
- A, C, G, and T represent the bases in RNA - False. In RNA, thymine (T) is replaced by uracil (U).
- The two polynucleotide chains of RNA twist into a double helix shape - False. RNA is primarily single-stranded.