BIO102 – Introductory Biology
July-August 2022
Module 2: Genes and Development
From Genotype to Phenotype (part1)
DNA or proteins the hereditary molecules?
How information in DNA is stored?
How DNA is copied?
How information hidden in DNA is decoded?
How DNA governs inheritance?
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Simple beginning………
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……….Complex phenotypes
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Variations in Genotypes
Variations in Phenotypes
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Variations in Phenotypes
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E. coli 0157:H7 Genome
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Proteins, proteins, proteins…
Each unique organism has a common as well as
distinct set of proteins (“PROTEOME”)
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DNA or proteins the hereditary molecules?
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Bacteriophages
(bacteria eaters!)
Head, neck, collar, sheath and tail
Of T2 are all made up of PROTEINS
DNA inside the “head”
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The Hershey-Chase
Experiment
- Use bacteriophage T2
- Label protein with 35S
(methionine & cysteine)
- Label DNA with 32P
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Hershey-Chase experiment demonstrates that T2 DNA
contains INFORMATION required to make more copies of T2
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How information in DNA is stored?
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INFORMATION stored in DNA is unique in species
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We are all different!
6.4 billion base-pairs of DNA!!
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INFORMATION is stored in DNA!!
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How DNA is copied?
How information hidden in DNA is decoded?
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Phenotype
The Central Dogma
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Phenotype
The Central Dogma
Process Enzyme
Replication DNA Polymerase
Transcription RNA Polymerase
Translation Ribosome!
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Phenotype
The Central Dogma
Environment
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Phenotype
The Central Dogma
Process Enzyme
Replication DNA Polymerase
Transcription RNA Polymerase
Translation Ribosome!
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DNA Replication
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REMEMBER!
DNA/RNA synthesis always occurs in 5’3’ direction!
Protein synthesis always occurs NC terminal!
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REMEMBER!
DNA/RNA synthesis always occurs in 5’3’ direction!
Protein synthesis always occurs NC terminal!
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DNA Replication is
“SEMI-CONSERVATIVE”
Evidence provided by the
Meselson & Stahl experiment!
(Chapter 11; p221)
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OK…but how does DNA replication start?
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DNA Synthesis
Leading strand – Continuous
Lagging strand – Discontinuous
REMEMBER
DNA synthesis is always 5’3’
Okazaki fragments
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DNA Synthesis
Leading strand – Continuous
Lagging strand – Discontinuous
Okazaki fragments
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The “Replication Fork”
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DNA Proofreading
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DNA Proofreading
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DNA Proofreading
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IMPACT: 1 change per Genotype
1 billion to Phenotype
base pairs ofI replicated DNA! 36
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Polymerase Chain Reaction (PCR)
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DNA is the Genetic Material!
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The Process
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Jurassic Park - CONCEPT
Inject “dinosaur” nucleus
into a fertilized egg whose
own nucleus has been
removed.
Grow embryo in
surrogate mother!!
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Reading
Life – The Science of Biology (9th Ed)
Ch 13: p266-288, Ch 14: p290-308 Life 9th Ed
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