RNA AND PROTEIN SYNTHESIS RNA vs DNA 1

RNA AND PROTEIN SYNTHESIS RNA vs DNA 1. 2. 3. 4. 5. RNA 5 – Carbon sugar (ribose) Phosphate group Nitrogenous base Single stranded Uracil base DNA 5 – Carbon sugar (deoxyribose) Phosphate group Nitrogenous base Double stranded Thymine base

RNA MOLECULE

TYPES OF RNA Messenger RNA (m. RNA) • Carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell Ribosomal RNA (r. RNA) • Makes of the major part of a ribosome Transfer RNA (t. RNA) • Transfers amino acids to ribosomes during protein synthesis

TRANSCRIPTION • Transcription The process of producing RNA molecules by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA Requires the enzyme RNA polymerase • Binds to and separates the DNA strands • Uses one strand of DNA as a template to form RNA • Binds to regions of DNA known as promoters which have specific base sequences • Promoters are signals in DNA that indicate to the enzyme where to start and stop making RNA

GENE: coded DNA instructions that control the production of proteins in the cell

RNA Editing RNA molecules have sections called… • Introns: sections not coded for making proteins “cut” out or edited while still in the nucleus • Exons: sections coded for making proteins “spliced” back together to form final m. RNA

THE GENETIC CODE The Genetic Code • The language of m. RNA instructions • Consist of 20 different amino acids • With 64 possible codons Codon: consist of 3 consecutive nucleotides that specify a specific amino acid (3 bases long) Proteins are made by joining amino acids into long chains called polypeptides • The property of a protein is determined by the order in which different amino acids are joined together to form polypeptides

TRANSLATION • Translation The decoding of an m. RNA message into a polypeptide chain (protein) Takes place on ribosomes in the cytoplasm • • • Begins when m. RNA in the cytoplasm attaches to a ribosome Each codon of the m. RNA moves through the ribosome Proper amino acid is brought into the ribosome by t. RNA Amino acid is transferred to growing polypeptide chain in the ribosome Each t. RNA carries only one kind of amino acid Each t. RNA has 3 unpaired bases called anticodons which are complementary to one m. RNA codon Works like an assembly line Polypeptide chain continues to grow until the ribosome reaches a stop codon Polypeptide chain is released Protein

TRANSLATION

PROTEIN SYNTHESIS

• Protein PROTEINS Enzymes that catalyze and regulate chemical reactions Act as microscopic tools to build or operate a component of a living cell Genes code for proteins that in turn determine genetic traits

Mutation • • MUTATIONS Changes in the genetic material Effect on organism Most effects are neutral Some effects are deadly Some lead to greater genetic variability in a species Causes Random mistakes during DNA replication or RNA transcription Prolonged exposure to excessive radiation or harmful chemicals Types of Mutations Point mutation: gene mutations involving changes in one or a few nucleotides • Occur at a single point in the DNA sequence • Include substitutions, insertions and deletions Substitution: one base is changed to another Insertions: base is inserted into the DNA sequence Deletion: Base is deleted from the DNA sequence

Frameshift mutation: mutations that shift the “reading” frame of the genetic message by inserting or deleting a nucleotide • May change every amino acid that follows the point of mutation • Protein may be altered so much that it is unable to perform its normal function • May lead to termination of organism (death) Chromosomal mutation: involves changes in the number or structure of chromosomes • • • May change the locations of genes on chromosomes DELETIONS: involve the loss or all or part of a chromosome DUPLICATION: produce extra copies of parts of a chromosome INVERSION: reverse the direction of parts of a chromosome TRANSLOCATION: part of one chromosome breaks off and attaches to another • Significance of Mutations Most are neutral Some are harmful • Causes of genetic disorders • Causes of many types of cancer Some lead to greater genetic variability in a species • Polyploidy: organism has extra sets of chromosomes (3 N or 4 N) • Can cause plants to be stronger and larger