Classical and Modern Genetics

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Classical and Modern Genetics

• Chapter 23

Great Idea All living things use the same
genetic code to guide the chemical reactions in
every cell.
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Chapter Outline

• Classical Genetics
• DNA and the Birth of Molecular Genetics
• The Genetic Code

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Classical Genetics
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Classical Genetics

• Mendel
• Basic laws of inheritance
• Classic pea plant experiments
• Purebred
• Hybrid
• Results
• First generation
• Second generation
• Gene
• Dominant
• Recessive

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Rules of Classical Genetics

• Traits (genes) are passed from parent to
  offspring
• mechanism unknown
• Two genes for each trait
• One from each parent
• There are dominant and recessive genes
• Dominant expressed

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Qualitative versus Quantitative Genetics

• Qualitative
• observational
• Quantitative
• Predictive model
• Used to trace genetic disease

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DNA and the Birth of Molecular Genetics
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Nucleotides The Building Blocks of Nucleic Acids

• Nucleotide
• Three molecules
• Sugar
• DNA deoxyribose
• RNA ribose
• Phosphate ion
• Base
• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Thymine (T)

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DNA Structure

• Join nucleotides
• Alternating phosphate and sugar
• DNA
• 2 strands of nucleotides
• Joined by base pairs
• Bonding pattern
• AdenineThymine
• CytosineGuanine

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DNA Structure
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RNA Structure

• Differences
• One string of nucleotides
• Sugar is ribose
• Thymine replaced by uracil
• Uracil (U) bonds with adenine

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The Replication of DNA

• DNA replication
• Occurs before mitosis meiosis
• Process
• DNA double helix splits
• New bases bond to exposed bases
• Result
• Two identical DNA strands

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The Genetic Code
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Transcription of DNA

• Transcription
• Information transport
• Uses RNA
• Process
• Unzip DNA
• RNA binds to exposed bases
• RNA moves out of nucleus (mRNA)

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The Synthesis of Proteins

• tRNA
• Reads message
• Structure
• Amino acid
• 3 bases
• Process
• mRNA moves to ribosome
• rRNA aligns mRNA and tRNA
• tRNA matches codon on mRNA
• Amino acid chain forms
• Basis for protein

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Protein synthesis cont.

• One gene codes for one protein
• Protein drives chemical process in cell
• DNA
• Introns
• Exons
• All living things on Earth use the same genetic
  code

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Mutations and DNA Repair

• Mutations
• Change in DNA of parent
• Causes
• Nuclear radiation
• X-rays
• UV light
• DNA Repair
• 10,000 hits per day
• Cells repair damage

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Why Are Genes Expressed?

• Gene control
• Turning genes on and off
• Each cell contains same genes
• Not all cells have same function
• Certain genes activated
• Scientists currently studying how

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Viruses

• Virus
• Not alive
• No metabolism
• Cannot reproduce on own
• Structure
• Short DNA or RNA
• Protein coating
• How it works
• Taken into cell
• Takes over cell
• Produces more copies
• Kills cell

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HIV

• Human Immunodeficiency Virus (HIV)
• Contains RNA
• Codes back to DNA
• DNA incorporated into cell
• Makes new viruses
• Cell dies
• Complex
• Two protein coats
• Outer coat fits T cell receptors
• Inner coat encloses RNA

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Viral Epidemics

• Viruses
• Cannot use medication
• Use vaccination
• Viruses evolve rapidly
• HIV
• Influenza
• SARS
• Bird flu