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Central Dogma: Molecular Gene2cs Take home points: An organism’s phenotype is dependent on its genotype The central dogma describes the flow of biological informa2on in a cell Structure of DNA & RNA impacts their func2on DNA & RNA are polymers 1
From Mendelian Genetics to Molecular Genetics
  Recall Genetic lessons from BIOL 180:
Alleles are associated with phenotype
Alleles (different forms of a gene) are inherited
Chromosome theory of inheritance
chromosomes are composed of genes
alleles on different chromosomes assort independently
Theory of natural selection
heritable variation
differential reproductive success
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Brainstorm with your neighbor: What do we need to know to understand how genotype leads to phenotype at the molecular level? 3
From Mendelian Genetics to Molecular Genetics
Next several weeks in BIOL 200
Molecular basis for inheritance
Molecular basis for heritable variation
Molecular basis for phenotype
How are these processes - inheritance & gene expression regulated in cells
in response to environmental conditions?
through the cell cycle?
through development?
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Figure 15-4
Slide 1
Central Dogma Describes the Flow of Biological Information
(a) Genetic information flows from DNA to RNA to proteins.
DNA
(information
storage)
Figure 15-4
(a) Genetic information flows from DNA to RNA to proteins.
DNA
(information
storage)
TRANSCRIPTION
mRNA
(information
carrier)
Slide 2
Figure 15-4
(a) Genetic information flows from DNA to RNA to proteins.
DNA
(information
storage)
TRANSCRIPTION
mRNA
(information
carrier)
Proteins
(melanocortin
receptor)
TRANSLATION
Slide 3
Figure 15-4
(a) Genetic information flows from DNA to RNA to proteins.
DNA
(information
storage)
GENOTYPE
TRANSCRIPTION
mRNA
(information
carrier)
Proteins
(melanocortin
receptor)
TRANSLATION
Forest mouse
PHENOTYPE
Physical traits
that are a
product of
the proteins
produced.
Mice with this DNA sequence have
dark coats.
Slide 4
DNA sequence = genotype
(b) Differences in genotype may cause differences in phenotype.
Beach mouse
PHENOTYPE
Physical traits
that are a
product of
the proteins
produced.
Mice with this DNA sequence have
light coats.
How could a mouse with light coat color have evolved?
Figure 15-4
(a) Genetic information flows from
DNA to RNA to proteins.
(b) Differences in genotype may
cause differences in phenotype.
DNA
(information
storage)
GENOTYPE
TRANSCRIPTION
TRANSCRIPTION
TRANSLATION
TRANSLATION
mRNA
(information
carrier)
Proteins
(melanocortin
receptor)
Forest mouse
Beach mouse
PHENOTYPE
Physical traits
that are a
product of
the proteins
produced.
Mice with this DNA sequence
in their melanocortin receptor
gene have dark coats.
Mice with this DNA sequence
in their melanocortin receptor
gene have light coats.
Excep2ons to central dogma 1. 2. Where do the steps in the central dogma take place? Prokaryote
Eukaryote
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Overview of Next Lectures • 
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Structure & func2on: Nucleic Acids DNA replica2on – in class ac2vity DNA repair & muta2ons Transcrip2on Transla2on – in class ac2vity Structure & func2on: proteins 13
Figure 4.1
Structural features of nucleotides,
nucleic acid monomers
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Figure 4.1
Which are in RNA?
Nucleic acid monomers: NTPs or dNTPs
Which are in DNA?
How will you remember which are
pyrmidines and which are purines?
R
D
“Stones were CUT
to build a single Pyramid”
(PYRIMIDINES)
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Figure 3.4
From monomers (single building blocks)
to polymers
Monomer = nucleotide, amino acid, or sugar
Mon
ome
r
Polymer
Monom
er
Monomer
Monomer
Monomer
Monomer
Monomer
Monomer
Monomer
Polymerization
(bonding together of
monomers)
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Figure 3.5
Polymerization
(build)
Depolymerization
(breakdown)
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Figure 4.2 From nucleotide monomers to polymer
POLYMERIZATION of nucleic acids = Formation of phosphodiester bonds
Note how the
ribose C3 and C5
are involved
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Figure 4.3
RNA and DNA Have a Sugar Phosphate Backbone
U
How would you write the base sequence?
´
G
A
Is this DNA or RNA?
C
What 2 characteristics told you?
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Figure 4.6
DNA strands
are
ANTIPARALLEL
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How do we know the structure of DNA?
Key discovery by Erwin Chargaff: number of purines = number of pyrimidines
Model building by James Watson and Francis Crick (using Rosalind Franklin’s data)
A short, clear paper that changed the world
April 25, 1953
Watson, J.D. and Crick. F.H.C.
A structure for Deoxyribose Nucleic Acid
Nature 171: 737-738.
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Key differences between RNA & DNA structure DNA
RNA
What DNA Really
Looks Like in
Eukaryotic Cells
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Genome Projects of some eukaryotic organisms
2002
S.cerevisiae
budding yeast
2004
R. norvegicus
Rat
Rice
Anopheles - mosquito
M. Musculus Mouse
1996
C. elegans
nematode
2004--->
Multiple species
fungi, Insects
Other:
Invertebrates
Vertebrates
Plants
A. thaliana
crucifer
1998
2001
H. Sapiens
2000
Nigeria
D. melanogaster
Fruit fly
2000
Japan
Europe
China
Americas
Central Dogma: Molecular Genetics
You should be able to: Describe the flow of informa2on in a cell from DNA to protein Recognize excep2ons to the central dogma Compare and contrast the structure & func2on of RNA & DNA Predict how stable a double-­‐stranded DNA molecule is based on its DNA sequence Explain the molecular rela2onship between genotype & phenotype Compare and contrast the cellular loca2ons of replica2on, transcrip2on and transla2on for prokaryotes and eukaryotes Predict the consequences of disrup2ng any step in the processing of DNA to protein VOCABULARY
Nucleotide, phosphate group, hydroxyl group, hydrogen bond,
nitrogenous bases, ribose vs deoxyribose, 5’ vs 3’
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