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DNA and the language of life
Structure of DNA
Building blocks are nucleotides
3 Parts of a nucleotide:
1. Deoxyribose sugar
2. Phosphate
3. Nitrogen base
–
–
–
–
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
The Double Helix
• Discovered by Watson and Crick
& Wilkins and Franklin
• Deoxyribonucleic Acid
• Alternating sugar-phosphate
backbone
• Base pairs are attached at the
sugars
• Hydrogen bond (weak) holds bases
pairs to one another
– A bonds with T
– C bonds with G
The Double Helix
DNA Replication
• Making exact copies of
our DNA
• Occurs in the nucleus of
our cells
• Semi- Conservative
– Newly created DNA contains 1
original and 1 new strand
– Each parent strand acts as a
template to create a new
complementary strand
– Ensures identical copies
DNA Replication
• Begins at replication forks
• Replicates in both directions
• Dozens of enzymes are involved
– DNA Helicase unwinds the helix
– DNA Primase provides a starting point of DNA for DNA polymerase
to begin synthesis of the new DNA strand.
– DNA Polymerase adds new complementary nucleotides to create the
new strand
– DNA Ligase seals up any gaps or breaks in the newly created strands
• In humans, DNA is copied at about 50 base pairs per second. The
process would take a month (rather than the hour it actually does)
without ENZYMES.
• DNA polymerase makes very few errors, and most of those that are
made are quickly corrected by DNA polymerase and other enzymes
that "proofread" the nucleotides added into the new DNA strand.
• With this system, a cell's DNA is copied with less than one mistake
in a billion nucleotides. This is equal to a person copying 100 large
(1000 page) dictionaries word for word, and symbol for symbol,
with only one error for the whole process!
• http://www.youtube.com/watch?v=oNW_ykH3AvA
• funny, more detail than necessary (The Office)
• https://www.youtube.com/watch?v=TNKWgcFPHqw