RNA and Protein Synthesis

• Lesson Objectives


  1. Describe the structure of DNA and differentiate the 3 types of RNA

  2. Determine the complementary strand of DNA and mRNA that can be transcribed from DNA

  3. Relate the uniqueness of an individual based on the role found in DNA
• One of the 4 macromolecules essential for life is DNA
• DNA


  Consists of a deoxyribose sugar, a phosphate group, and a nitrogenous base
• Building blocks of DNA

  • Nucleotides consisting of purines (ADENINE and GUANINE) and pyrimidines (CYTOSINE and THYMINE)
• RNA in Protein Synthesis

  Serves as a mediator of DNA and protein, dictates what proteins are to be synthesized, becomes part of ribosomes that create proteins, and moves amino acids to the ribosomes
• The synthesis of proteins is important in cells as it provides necessary structural components and enzymes for producing other organic molecules
• In 1953, James Watson & Francis Crick unveiled the 3-dimensional double helix structure of a DNA molecule
• DNA model


  • Double helix structure with strands connected by hydrogen bonds, Adenine pairs with thymine, and cytosine pairs with guanine
• Chargaff’s rule states that the total number of purines in a DNA molecule is equal to the total number of pyrimidines
• The DNA double helix is antiparallel, with the 5’ end of one strand paired with the 3’ end of its complementary strand
• The DNA base pairs are connected by hydrogen bonds, and the outer edges of the nitrogen-containing bases are exposed for possible hydrogen bonding
• RNA


  Named after the 5-carbon sugar group ribose, adenine pairs with uracil, found in the nucleus and cytoplasm, and consists of messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
• mRNA


  Single-stranded RNA molecule complementary to one strand of DNA, leaves the nucleus to the cytoplasm for protein synthesis, and contains codons for translating genetic code into proteins
• rRNA


  Single-stranded RNA molecule found in cells, part of the protein-synthesizing organelle ribosome, synthesized in the nucleus, and combines with ribosomal proteins to form ribosome subunits
• tRNA


  RNA molecule that helps decode information in mRNA sequences into specific proteins, encoded by DNA in the cell nucleus, and transcribed with the help of RNA polymerase III
• Ribosomal Ribonucleic Acid (rRNA)


  • It helps to decode information present in mRNA sequences into specific proteins
  • It is encoded by DNA in the cell nucleus and transcribed with the help of RNA polymerase ΙΙΙ
  • The structure of tRNA folds upon itself and creates an intra complementary base pairing which gives rise to hydrogen-bonded stems and associated loops that contains nucleotides with modified bases
  • The structure in two-dimensional resembles a cloverleaf having three loops and an open end and are usually 75-90 ribonucleotides in length
• Transfer Ribonucleic Acid (tRNA)

  • It transfers information from DNA to a protein, called gene expression
  • It consists of two subunits: the large and small subunits
  • Initiation occurs at the 1st AUG in the MRNA strand that codes the amino acid methionine on AUG. It occurs when the enzymes RNA polymerase binds to a region of a gene called the promoter
  • Elongation is the addition of nucleotide to mRNA strand
  • Termination is the ending of transcription
• Human grows and develop according to the instructions in our genes
• The code dictates the order by which the amino acids will be assembled to form a protein. DNA codes for the structure of the protein and the protein’s structure, in turn, will determine its role in the body
• All cells must carry the same genetic information
• REPLICATION is the process by which a copy of the original genetic information is duplicated so that each new cell receives exactly the same information as that of the parent cell
• DNA explains both unity and diversity among living things
• Each human is created to become humans but each with a different recipe, which explains our uniqueness and distinctive features. This recipe is the secret code found in our DNA
• The recipe for cooking the protein needed by the body is only confined in the nucleus of the cell
• Proteins are made up of chains of amino acids called polypeptides
• The transfer of information from DNA to a protein is called gene expression
• TRANSCRIPTION


  1. Rewrites the genetic code in DNA into a messenger RNA. It works just like DNA replication and follows the base pairing principles except adenine in DNA pairs with uracil in RNA

  2. When transcription is finished, the DNA recoils to its double helix structure

  3. The mRNA carries the code to the waiting ribosomes in the cytoplasm
• TRANSLATION


  1. Occurs at the ribosome, which consists of rRNA and proteins

  2. The instructions in mRNA are read, and the tRNA brings the correct sequence of amino acids, producing a polypeptide chain

  3. After a polypeptide chain is synthesized, it may undergo additional processing to form the finished protein and deliver to different parts of the body
• For instance, your hair cells will make protein for your hair. The segment of DNA (gene) responsible for your hair will be transcribed into an mRNA strand