Chapter 17 - Nucleic Acids and Protein Synthesis

17.1 - Components of Nucleic Acids

• The unbranched nuclear chains are nucleotides, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

• A nucleoside is a pentose sugar and a base combination

• There are three components of a nucleotide: a pentose, a base, and a phosphate group.

• In DNA, adenine, thymine, guanine, or cytosine may be the base of sugar.

  • In the RNA, adenine, uracil, guanine or cytosine can be the basis.

  

17.2 - Primary Structure of Nucleic Acids

• Each nucleic acid has a unique base sequence called its primary structure.
  • In nuclear acid, the 3′OH group of each RNA or DNA deoxyribose ribose is a phosphodiester link in the following nucleotide to the phosphate group of the 5′or sugar carbon atom to produce a backbone of the sugar and phosphate alternating groups.
  • At one end of nucleic acid, there is a free five′′ phosphate and at the other end, there is a free 3′′ OH.

17.3 - DNA Double Helix and Replication

• A DNA molecule is composed of two nucleotide strands that, like a spiral step, are wounded around one another.
  • Hydrogen bands between additional foundation pairs, A, T, and G, C hold the two strands together.
• DNA polymerase makes new DNA strands on each original DNA strand, which serve as templates, during the replication of DNA.
• The additional base combination ensures that the bases have been correctly paired, to provide the same DNA copies.

17.4 - RNA and Transcription

• Three types of RNA vary depending on their function in the cell

  • Ribosomal RNA is mostly the ribosomal structure, messenger RNA carries genetic data from the DNA into the ribosome, and RNA is translated into a growing peptide chain and the correct amino acids.

• The process through which RNA polymerase produces mRNA on one strand of DNA is transcription.

• The foundations of mRNA are complementary to DNA, except that A in DNA and U in RNA are matched.

• mRNA is produced when certain proteins are necessary in the cell.

  

17.5 - The Genetic Code and Protein Synthesis

• The genetic code consists of a number of codons, three-base sequences that specify the order in a protein for amino acids.
  • The 20 amino acids have 64 codons, meaning that most amino acids have multiple codons.
• The AUG codon indicates beginning the transcription, which is stopped by the UAG, UGA, and UAA codons.
  • Protein is synthesized in the ribosomes in three steps: initiation, chain elongation, and termination.
• tRNAs provide the right ribosome amino acids and peptide bonds during translation to join amino acids to a peptide chain.
  • The polypeptide is released and becomes a functional protein in the cell and takes on its secondary and tertiary structures.

17.6 - Genetic Mutations

• A genetic mutation is a change in one or more DNA sequence bases that can change the proper function of the structure and ability of the resulting protein.
• A codon is altered in a point mutation, and a base that changes all codons after the base changes is added or deleted in an insertion or deletion mutation.

17.7 - Recombinant DNA

• A recombinant DNA is produced by inserting a DNA segment—a gene- into E. coli bacteria's plasmid DNA
  • The protein expressed by the foreign DNA segment is produced as the changed bacterial cells replicate.
• The Polymerase Chain Reaction produces large amounts of DNA in criminal investigations.

17.8 - Viruses

• DNA or RNA viruses must invade host cells to synthesize more viruses using machinery in cells.
  • The viral DNA is synthesized in the host cell with the nucleotides and enzymes for a retrovirus containing RNA.
• In AIDS treatment, inhibitors block the entry into the cell by the virus, nucleoside analogs inhibit the reverse HIV transcriptase and protease inhibitors interrupt the protease catalytic activity needed to produce proteins to synthesize more viruses.