Nucleic Acids and Protein Synthesis

Central Dogma DNA  RNA  Protein  Trait

DNA to PROTEINS DNA is the blueprint for life – it contains your genetic information The order of the bases in a segment of DNA (Gene) codes for a particular protein; these proteins then determine your traits How do you get from a 4-letter code to an entire organism? A GENE IS A SEGMENT OF DNA THAT CODES FOR A PROTEIN. NOT ALL DNA CODES FOR PROTEINS.

DNA to RNA: TRANSCRIPTION In the first step of protein synthesis, the code of DNA is transcribed onto a molecule of RNA – this step of the process is known as Transcription DNA is too big and too sensitive to leave the nucleus. However, proteins are made in the ribosomes, so the information in DNA must be transferred. It will be transferred to a molecule of RNA RNA is also used because it allows the genetic information to move from the nucleus (safe) to the cytoplasm (dangerous)

RNA RNA = Ribonucleic acid It is still a nucleic acid – therefore it is made up of nucleotides (3 components: sugar, phosphate group and nitrogen bases) It uses ribose as its sugar Instead of using thymine, it uses uracil (A, U, G, C) It is a single strand only

Types of RNA - mRNA Messenger RNA (mRNA): single uncoiled chain that carries the genetic information from the nucleus to the cytosol

Types of RNA - tRNA Transfer RNA (tRNA): single chain in the formation of a hairpin shape, each piece is bound to a specific amino acid

Types of RNA - rRNA Ribosomal RNA (rRNA): most abundant form, wraps around ribosomal proteins to make up the ribosomes where proteins are made

Transcription Process by which genetic information is copied (transcribed) from DNA to RNA RNA polymerase initiates transcription by binding to a specific area of DNA called promoters What do you think a promoter is? A promoter starts, or promoters the beginning of transcription Where the polymerase binds, the DNA strands separate and a template is created upon which RNA is created

Transcription (continued) RNA polymerase attaches to the first nucleotide and adds on complementary bases using uracil instead of thymine Continues until the polymerase reaches the termination signal What do you think a termination signal does? Termination signal causes the polymerase to release the DNA and RNA

Protein Synthesis When mRNA is produced it will be used in protein synthesis or the production of proteins Proteins consist of polypeptides which consist of amino acids There are 20 possible amino acids

Translation: Protein Assembly This process takes the information that was transcribed into mRNA and translates it into a protein It begins when a piece of mRNA attaches to a ribosome mRNA is “read” by the ribosome. It is read in segments of 3 letters called codons Each codon codes for a specific amino acid. That amino acid is brought by a piece of tRNA which “transfers” amino acids. tRNA is also read in segments of 3 letters called anticodons. The anticodon is complementary to the codon found on mRNA ( i.e. if the codon is AUG the anticodon is UAC) Eventually a stop codon is reached. They do not code for amino acids. They tell the ribosome to stop adding amino acids. Many ribosomes may work at once on one piece of mRNA

Genetic Code Correlation between nucleotides and amino acids Codon: 3 mRNA nucleotides; codes for a specific amino acid One codons codes to start (AUG – amino acid Methionine) and 3 codons can stop (UAA, UAG, UGA – no amino acids) If you had a codon AAG, what amino acid would you have? lysine