DNA, RNA, and Proteins

• The central dogma is the flow of genetic information from DNA to RNA to Protein
• DNA is double helical in structure
• Each nucleotide is composed of a nitrogenous base, phosphate, and a five-carbon sugar (deoxyribose)
• Nitrogenous bases: purine bases (adenine and guanine) and pyrimidine bases (cytosine and thymine)
• Adenine pairs with thymine while cytosine pairs with guanine
• DNA is discovered by James Watson and Francis Crick
• DNA is the blueprint for life
• DNA stands for Deoxyribonucleic Acid
• In the first step of DNA replication, an enzyme DNA topoisomerase untangles the coils (DNA Replication)
• (2) Enzymes called “Helicase” unzip the DNA molecule exposing both strands of nitrogenous bases. The DNA is separated into two strands.
• (3) DNA polymerase pairs the bases A-T and G-C. It checks work and corrects mistakes. Nucleotides are paired.
• (4) DNA ligase (enzyme) follows behind and bonds the nucleotides together. Lastly, Two strands of DNA are created.
• DNA replication begins at specific sites called origins of replication
• RNA stands for Ribonucleic Acid
• RNA is single-stranded and shorter
• Each nucleotide contains a different sugar: ribose instead of deoxyribose
• Bases are A, G, C, and U (uracil) A pairs with U; G pairs with C
• 3 different RNA molecules involved in protein synthesis: mRNA (messenger RNA), rRNA (ribosomal RNA), and tRNA (transfer RNA)
• The central dogma involves transcription and translation
• Transcription occurs in the nucleus of the cell
• (1) DNA unwinds in section
• (2) mRNA (messenger RNA) is formed by base pairing with the parent strand of DNA. This begins transcription.
• (3) mRNA carries the message about what type of protein to make from the DNA in the nucleus to the ribosome
• (4) Once mRNA is formed, enzymes in the nucleus remove the Introns (noncoding message) and leave the Exons (good message)
• Each 3 consecutive bases on the mRNA is a code word, codon, that specifies an amino acid
• The genetic code consists of 64 codons, but only 61 code amino acids
• Three codons (UAA, UAG, UGA) act as signal to stop the process
• One codon, AUG, codes for methionine, and is the start signal for translation
• Translation occurs in the cytoplasm and ribosome of the cell
• (1) mRNA leaves the nucleus and migrates to ribosome
• (2) mRNA binds to small ribosomal subunit
• (3) tRNA brings an amino acid to the ribosome, where anticodon on the tRNA binds to the codon of the mRNA
• (4) The amino acid bonds to its adjoining amino acid to form a growing polypeptide molecule
• (5) The tRNA without the amino acid is released from the ribosome
• (6) Other tRNA’s bring amino acids to the ribosome to complete the protein molecule
• Translation is the process of synthesizing a code from amino acids, according to the sequences of the nucleotides in mRNA.
• Transcription is the process of copying the DNA into RNA, which is the first step in protein synthesis
• Ribosomal RNA is needed for protein synthesis – helps mRNA bind to the ribosome
• tRNA, brings specific amino acids to the ribosome to be assembled as proteins
• Mutations are the changes in the DNA sequence, that may be

  passed along to future generations