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 - 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 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

Translation (cont) - example (cont): mRNA strand broken into codons mRNA strand broken into codons Amino Acid Sequence = a protein Amino Acid Sequence = a protein Chart

Translation (cont) - example (cont): mRNA strand broken into codons mRNA strand broken into codons Amino Acid Sequence = a protein Amino Acid Sequence = a protein Chart

Central Dogma = the flow of information from DNA to RNA to proteins - involves the three main processes: replication transcription transcriptiontranslation

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 effect the end outcome of what amino acid is produced Chart

Mutation Examples - Harmful

Mutation Examples - Beneficial Coronary Heart Disease Blockage of the Coronary Artery supplying blood to the heart Mutation helps protect people from blocked arteries

Mutation Examples - Beneficial Sickle Cell Disease - homozygous recessive disease - die if you get it People who are heterozygous for this disease don’t die of sickle cell disease or malaria

Malaria

Mutations (cont) - mutations in body cells affect only the organism itself and are not passed to offspring

Mutations (cont) - mutations in sex cells (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, industry 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 Her book helped launch the environmental movement.