DNA and Polypeptide Synthesis

DNA and Polypeptide Synthesis Model the process of polypeptide synthesis, including: (ACSBL079) – – – – transcription and translation assessing the importance of mRNA and tRNA in transcription and translation (ACSBL079) analysing the function and importance of polypeptide synthesis (ACSBL080) assessing how genes and environment affect phenotypic expression (ACSBL081) Polypeptide A linear organic polymer consisting of a large number of amino-acid residues bonded together in a chain, forming part of (or the whole of) a protein molecule. When amino acids combine, they form polypeptide chains. When polypeptide chains combine, they form proteins. Polypeptide synthesis occurs through transcription and translation In eukaryotes these two stages occur one after the other, whereas in prokaryotes these two stages occur at the same time. Stage 1: TRANSCRIPTION (occurs in nucleus) 1. Initiation: Double stranded DNA unwinds a section. 2. Elongation: RNA polymerase moves along strand attaching loose RNA nucleotides to DNA (AU and C-G). Question: Complete AGGCUCAGCU during RNA UCCGAGUCGA 3. Termination: Makes strand of mRNA which leaves nucleus into cytoplasm. Stage 2: TRANSLATION (occurs in cytoplasm) 1. Initiation: Ribosomes bind to mRNA and produce corresponding tRNA anticodon (has complementary nitrogenous bases to those in mRNA). The anticodon has a specific amino acid. 2. Ribosome continues to move along mRNA to produce more tRNA molecules. 3. tRNA releases amino acids to attach to ribosome. tRNA leaves to find another amino acid in cytoplasm. Ribosome moves along mRNA -> forms tRNA -> forms amino acids -> amino acids attach themselves onto the Ribosomes How are amino acids formed? During translation the ribosomes move along the mRNA so that they can produce more tRNA. The tRNA releases amino acids. 4. Elongation: As ribosome move along mRNA, more amino acids are attached and linked by peptide bonds. 5. Termination: Stop codon = polypeptide chain released into cytoplasm and either: Folds to form protein (one polypeptide folds around itself to form a protien) OR Bonds with other polypeptides and then folds to form protein. Importance of mRNA and tRNA in transcription and translation Messenger RNA (mRNA) carries the genetic information copied from DNA in the form of a series of three-base code “words,” each of which specifies a particular amino acid. 2. Transfer RNA (tRNA) is the key to deciphering the code words in mRNA Importance of polypeptide synthesis They are the building blocks of proteins, which are essential to cell function. How genes and environment affect phenotypic expression ✓ An organism's phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes. The dominant genes that a person has greatly influence their phenotype. For example, a person with dominant genes for blue eyes, is most likely to have blue eyes. ✓ Environmental factors such as diet, temperature, oxygen levels, humidity, light cycles, and the presence of mutagens can all impact which of an animal's genes are expressed, which ultimately affects the animal's phenotype. Genotype: genetic makeup. Phenotype: appearance based on how genes are expressed. Investigate the structure and function of proteins in living things What is a protein? Proteins: complex macromolecules made of one or more polypeptides chains. Polypeptide chain: sequence of amino acids linked by peptide bonds. Primary structure: sequence of amino acids to form a polypeptide chain. Secondary structure: folding the polypeptide chain into a specific shape. Tertiary structure: further folding the polypeptide chain. Quaternary structure: protein contains 2 or more polypeptide chains. Function of protein Protein has many roles in your body. It helps repair and build your body's tissues, allows metabolic reactions to take place and coordinates bodily functions. In addition to providing your body with a structural framework, proteins also maintain proper pH and fluid balance. Functions of proteins?