Transcript DNA Unit
DNA Unit Structure of DNA - shape is a double helix - a long polymer made of smaller units (monomers) called nucleotides Structure of DNA (cont) - 4 different types of nucleotides - Adenine (A) - Guanine (G) - Cytosine (C) - Thymine (T) Structure of DNA (cont) - held together by hydrogen bonds - pairing rules: A binds with T G binds with C Discovery of DNA model of shape proposed by Watson and Crick - Discovery made 1953 - won Nobel Prize in 1962 - Discovery of DNA (cont) - Rosalind Franklin produced X ray photographs of DNA - helped Watson and Crick develop their model - Did NOT win Nobel Prize for her work Replication = the process of copying DNA - happens in the nucleus - DNA polymerases = enzymes that bond new nucleotides together Replication Replication Replication Replication (cont) - result is two identical strands of DNA - process has a proofreading system to correct errors Replication (cont) - example: Replication Transcription = process of copying information from DNA to mRNA (messenger RNA) - happens in the nucleus - RNA polymerases = enzymes that bond nucleotides to a mRNA strand Transcription (cont) - one side of the DNA (the template) is used - new rule: uracil (U) replaces thymine (T) - U binds with A (but only in RNA) Transcription Transcription Transcription Transcription (cont) - example: (template) Transcription (template) (mRNA) Translation = the process that converts info in mRNA into proteins - done by ribosomes in the cytoplasm - codon = 3 nucleotides together - each represents an amino acid Translation (cont) - example: (mRNA) Translation Translation (cont) - example (cont): Chart mRNA strand broken into codons Amino Acid Sequence = a protein Translation (cont) - example (cont): Chart mRNA strand broken into codons Amino Acid Sequence = a protein Central Dogma = the flow of information from DNA to RNA to proteins - involves the three main processes: replication transcription translation Mutations = a change in an organism’s DNA - they can be neutral (do nothing), harmful, or beneficial - a mutation may or may not effect the organism - depends on number of genes involved and location of mutation Mutation Examples - Neutral mRNA sequence is AAG Codes for Amino Acid mRNA sequence changes to AAA Codes for Amino Acid Mutation did not affect the end outcome of what amino acid is produced Chart Mutation Examples - Beneficial Coronary Heart Disease Blockage of the Coronary Artery supplying blood to the heart Mutation helps protect people from blocked arteries Mutations (cont) - mutations in body cells (SOMATIC) affect only the organism itself and are not passed to offspring Mutations (cont) - mutations in sex cells- GAMETES (egg and sperm) may be passed to offspring - most of the time this is bad, but not always - another source of genetic variation in organisms Mutations (cont) - Mutagens = agents in the environment that can cause a change in DNA - ex: UV Light, industrial chemicals Rachel Carson – one of the first ecologist to warn against the widespread use of pesticides and other potential mutagens and toxins in her book Silent Spring in 1962. Her book helped launch the environmental movement.