Whats So Special About DNA

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Whats So Special About DNA?
DNA is one of the most boring macromolecules
imaginable - its made of only four building
blocks and has a perfectly monotonous structure.
Worse yet, DNA just sits there - it doesnt
catalyze reactions or build the cell or organism.
So, whats so good about DNA?
The answer lies in DNAs ability to store and
copy information.
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How Can DNA Store and Copy Information?
Key properties that allow these neat tricks are
that DNA is a
double stranded molecule .
. held together by complementary bases ..
that pair through simple rules.
DNA is also capable of occasional change, and
occasionally, change is good.
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Winners of the Race to Learn DNAs Structure
Watson and Crick 53 Years Ago
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Building DNA Building Blocks
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DNA is Made of Two Long Chains of Nucleotides
Joined by Hydrogen Bonds
G and C are complementary as are A and T
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Two Views of the Double Helix
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DNA is Almost Always Wrapped Around Proteins
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Complementary Base Pairing Allows Each Strand of
DNA to Serve as a Template for DNA Replication
DNA is a perfect illustration of function
following form (structure dictates function).
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DNA Replication Something Old and Something New
In Each Daughter Molecule
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Simple As It Is in Principle, DNA Replication
Requires Many Enzymes That Work Coordinately
DNA polymerases are the first and foremost of the
replication enzymes.
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Accidents Happen With Some Accidents (Base
Mismatches) Leading to Mutation
A mutation is a heritable change in DNA sequence.
Mutations due to replication errors only happen
once in every billion replicated nucleotides.
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Mutation
Some mutation is good, too much is bad.
Cells employ elaborate mechanisms to prevent
mutation but the mechanisms arent perfect.
Mutations are the root cause of cancer (bad).
Mutations are the only way to introduce novel
alleles into a species (good for evolution).
The effects of mutation are usually bad or
neutral - only sometimes are mutations
beneficial.
So, just like Goldilocks not to hot, not too
cold, just right the optimal rate of new
mutation is a balancing act.
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DNA Damage is Often the Root Cause of Mutation
DNA is chemically altered (i.e. damaged)
spontaneously and by chemicals and radiation.
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Mutation as Villain
Cancerous growths that result from loss of a
protein that polices DNA for errors.
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Cancer Incidence Increases Sharply with Age
The increase is due at least in part to the
age-related accumulation of multiple mutations in
single cells.