Download Structure - Sonoma Valley High School

Structure of DNA and the
history of its discovery
Function of DNA
• DNA is the genetic
material of the cell
• The structure of DNA
must allow:
– the storage and
transmission of genetic
information
– exact replication to
occur.
Genes code for proteins
• Genetic information
must tell cells how to
make proteins.
– Sections of the DNA
called genes code for
one protein
– Proteins form
structures and
control chemistry of
cell.
Think: Proteins are made in the cytoplasm but DNA
remains in nucleus. How do you think that works?
Transformation
Think: What does this
picture show.
• The transfer of genetic
material
• Discover by Griffith
• Experiment injected mice
with disease causing &
non-disease causing
bacteria
• Found combination of dead
disease bacteria with live
non-disease still killed the
mice
• Later Avery discovered
DNA to be the agent
Discovery of DNA structure
• Rosalind Franklin took
pictures using X-Rays
in the 1930’s
James Watson Left &
Francis Crick right: Nobel
prize for DNA structure
• James Watson & Francis Crick
discovered double helix
structure of DNA in 1953 using
Fanklin’s pictures.
DNA Structure
• DNA is a polymer.
• The monomer of DNA is
called a nucleotide.
• Nucleotides linked
together to form the sides
of the DNA molecule.
• DNA molecule has shape
of a double helix.
– The sides are anti-parallel.
deoxyribonucleic acid
What’s in a name?
• One 5 carbon sugar
called deoxyribose.
– “Deoxy” = one less
oxygen.
– “ribo” = than ribose.
• Deoxyribonucleic acid
– “nucleic” = found in
nucleus.
– “acid” = acidic
Deoxyribose, a pentose sugar,
has each carbon numbered.
Nucleotide Structure
•Phosphate group attached to
the #5 carbon of the sugar.
•One nitrogenous base attached
to the #1 carbon in the sugar.
•Purines -2 rings
Adenine
Guanine
–Pyrimidines -1 ring
Cytosine
Thymine
Think: how will you recognize the
name of a base on a quiz?
Four bases of DNA
Complementary base pairing rules
• Nitrogenous bases form rungs of the helix.
– Adenine (2 rings) is bonded with Thymine (1 ring) using 2
hydrogen bonds. (A-T)
– Guanine (2 rings) is bonded with Cytosine (1 ring) using 3
hydrogen bonds. (G-C)
Think: how will you remember which
bases pair with each other?
Summary questions
1.
2.
3.
4.
Name 2 functions of DNA
Who discovered the structure of DNA?
What are the 4 base pairs.
What is the structure if DNA?