Download 1b Unit 5 DNA structure and replication powerpoint

The Secret Code
Genes
• Genes, which are sections of DNA, are
known to:
– Carry information from one generation to the
next.
– Put that information to work by determining
the heritable characteristics of organisms.
– Be easily copied, because all of a cell’s genetic
information is replicated (copied) every time
a cell divides.
How do we know that all of our
genetic information comes from
DNA?
Thanks to many scientists and many
experiments over the last ≈ 80 years.
• Griffith
• Hershey and Chase
• Franklin
• Watson and Crick
• Nucleic Acid:
Deoxyribonucleic
Acid (polymer)
• Made up of units
(monomers) called
nucleotides.
– Three components:
• 5-carbon sugar:
Deoxyribose
• A phosphate
group
• A nitrogenous
base
DNA
Nucleotide
DNA Structure
• Called a double helix
– Twisted Ladder
– Backbone (sides) :
5-carbon sugar
and phosphate
groups
– Rungs: nitrogenous
bases
Nitrogenous bases
• Our alphabet has 26 letters
– Can create many different words  many
different sentences  billions of different
books of information.
• DNA’s alphabet has 4 letters
– A, T, C, and G
– Create 3 letter words  Amino acids 
proteins  billions of different organisms
Nitrogenous bases
• Purines:
• Pyrimidines:
– Adenine
– Thymine
– Guanine
– Cytosine
DNA Replication
Replication: The process of making a copy of DNA
The “parent” molecule has two complementary strands of
DNA.
Each is base paired by hydrogen bonding with its specific
partner:
A with T and G with C
DNA Unzips
The first step in replication is the separation of the two
strands.
An enzyme called DNA helicase unzips DNA
New nucleotides added
Each parental strand now serves as a template that
determines the order of the bases along a new
complementary strand.
an enzyme called DNA polymerase adds the bases
Gaps are closed (zipped
closed)
The nucleotides are connected to form the sugarphosphate backbones of the new strands. DNA ligase
Each “daughter” DNA molecule consists of one parental
strand and one new strand….semi-conservative
• Reviewing DNA Replication
• Replication #2
• Replication #3 and more
Here are some interesting Facts!
• A single strand of DNA (one chromosome)
is about 2 inches long when uncoiled.
• Each human cell contains 46 chromosomes
(6 to 9 feet of DNA)
• Your body contains 75-100 trillion of cells.
• All of your DNA (when uncoiled and tied
together) could make about 6000 trips from
the Earth to the Moon.
A few more cool things about
DNA
• It takes about 8 hours for one of your cells to copy
all of its DNA.
• Our entire DNA sequence is called a
Genome…and there is an estimated 3,000,000,000
DNA bases
• This would take up about 3GB of storage
• If you could type 60 wpm, 8 hours/day…it would
take you 50 years to type this.
• 99.9% of our DNA is the same…it is the 0.01%
that makes you who you are!