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
= the process of copying DNA - happens in the nucleus Replication = the process of copying DNA - happens in the nucleus - DNA polymerases = enzymes that bond new nucleotides together TEM 500,000x
Replication
Replication
Replication
Replication (cont) - result is two identical strands of DNA - process has a proofreading system to correct errors
Replication (cont) - example: ATAGCTAGCTTC TATCGATCGAAG ATAGCTAGCTTC
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) Transcription (mRNA) ATAGCTAGCTTC TATCGATCGAAG - example: (template) Transcription (mRNA) ATAGCTAGCTTC TATCGATCGAAG ATAGCTAGCTTC UAUCGAUCGAAG
Transcription growing RNA strands one gene DNA TEM 13,000x
= the process that converts info in mRNA into proteins 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 Codon Codon
Translation (cont) - example: (mRNA) Translation UAUCGAUCGAAG
Translation (cont) UAU CGA UCG AAG Amino Acid Sequence = a protein Chart - example (cont): mRNA strand broken into codons Amino Acid Sequence = a protein UAU CGA UCG AAG
Translation (cont) Amino Acid Sequence = a protein UAU CGA UCG AAG Chart - example (cont): mRNA strand broken into codons Amino Acid Sequence = a protein UAU CGA UCG AAG Tyrosine Serine Arginine Lysine
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 Mutation did not effect the end outcome of what amino acid is produced Lysine Lysine Chart
Mutation Examples - Harmful
Mutation Examples - Beneficial Coronary Heart Disease Mutation Normal 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
- mutagens = agents in the environment that can cause a change in DNA 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 1962. Her book helped launch the environmental movement.