6.3.A—Describe the mechanisms by which genetic information flows from DNA to RNA to protein

Describe the mechanisms by which genetic information flows from DNA to RNA to protein.

• The sequence of the RNA bases, together with the structure of the RNA molecule, determines RNA function.
  • i. Messenger RNA (mRNA) molecules carry inf ormation from DNA in the nucleus to the ribosome in the cytoplasm.
  • ii. Distinct transfer RNA (tRNA) molecules bind specific amino acids and ha ve anticodon sequences that base pair with the codons of mRNA. tRNA is recruited to the ribosome during translation to generate the primary peptide sequence based on the mRNA sequence.
  • iii. Ribosomal RNA (rRNA) molecules are functional building block s of ribosomes.
• RNA polymerases use a single template strand of DNA to direct the inclusion of bases in the newly formed RNA molecule. This process is known as transcription.
• The enzyme RNA polymerase synthesizes mRNA molecules in the 5’ to 3’ direction by reading the template DNA strand in the 3’ to 5’ direction.
• In eukaryotic cells the mRNA transcript undergoes a series of enzyme-mediated modifications.
  • i. The addition of a poly-A tail makes mRNA more stable.
  • ii. The addition of a GTP cap helps with ribosomal recognition.
  • iii. The excision of introns, along with the splicing and retention of exons, generates different versions of the resulting mature mRNA molecule. This process is known as alternative splicing.