DNA: Structure and
History
Honors Biology
DNA is a chemical!!
Strawberries
Human
Functions of DNA:
-stores all your body’s
information
-Passes information from
parents to offspring
(heredity or hereditable characteristics)
DNA is made of smaller
parts called:
Nucleotides
•
Nucleotides
contain 3 parts:
–
–
–
Phosphate
Sugar
Nitrogen Base
Things to Know:
• There are four types of nitrogen
bases in DNA:
A- adenine
T- thymine
C- cytosine
G- guanine
Things to Know:
• There are two sides to
DNA
• Appears like a ladder:
– Sides are phosphate
and sugar
– Steps are the base
pairs
Base Pair Rule:
A-T are complimentary
C-G are complimentary
Can you see the ladder?
The DNA ladder is
twisted
This twist is called a “helix”
DNA is called the double helix
because it is a two sided, twisted
ladder.
History…
• 1952 – Rosalind Franklin used X-ray
diffraction to show helical structure of
DNA
The biggest event in DNA
history…
• 1953 – James
Watson and
Francis Crick
discover the 3-D
structure of DNA
The Basics
1. All living things
have DNA
2. The amount and
sequence (or order) of
ATGC makes us
different from each
other and other living
things
• 3. Small parts of the DNA that
contain a specific instruction is
known as a gene
4. Genes in the DNA are the
body’s directions for making
proteins
• Proteins make us:
– look the way we do
– function the way we do
– develop and grow the way we do
– behave the way we do
– think the way we do
•You and the person
next to you have
99.9% the same
DNA!!
How is that possible?
Discuss and Explain!!!
5. Chromosomes are:
• packaged DNA
• found in the nucleus of all
eukaryotic cells
6. All species have a set number of
chromosomes.
Humans= 46 chromosomes (23 pairs)
Fruit fly= 8 chromosomes
Rice = 12 chromosomes
Dog= 72 chromosomes
Yeast= 32 chromosomes
Goldfish= 100 chromosomes
Which of the following would
correspond to DNA, genes and
chromosomes?
Alphabet
Sentence
Words