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DNA
DNA Deoxyribonucleic Acid

A cell’s code / recipe / blueprint

Biological instructions that make
each species unique

Genetic instructions used in the
development and functioning of all
known living organisms
What Does DNA Look Like?

Similar to a ‘twisted ladder’

Each side of the ladder is made up of
SUGAR-PHOSPATE MOLECULES
– Sugar group  deoxyribose
– Phosphate molecule

Rungs(steps) of the ladder are nitrogen
bases
– DNA has 4 types of nitrogen bases

Nitrogen bases are connected by hydrogen
bonds
NITROGEN BASES

4 types of Nitrogen Bases
– Adenine (A)
– Thymine (T)
– Guanine (G)
– Cytosine (C)
NITROGEN BASES

Nitrogen bases occur in pairs in DNA.
– Adenine pairs with Thymine
– Guanine pairs with Cytosine

Like pieces of a puzzle, each base
bonds only with its correct partner.

If this code makes up one side of
the DNA, what would the code
be for the other side?
A
T
C
G
A
A
C
T
T
G
A
C
A
G
If this code makes up on side of
the DNA, what would the code
be for the other side?
A
T
C
G
A
A
C
T
T
G
A
C
A
G
T
A
G
C
T
T
G
A
A
C
T
G
T
C
NUCLEOTIDE
1 base + 1 Sugar + 1 Phosphate = Nucleotide
Who Discovered DNA?

James Watson and Francis Crick

Rosiland Franklin, a woman, discovered the double helix
shape of DNA and had the best X-ray picture at the time.

Maurice Wilkin, her colleague, didn’t want a woman to
get the credit for discovering DNA so he stole her picture
and gave it to Watson and Crick.

The picture along with their research help Watson and
Crick create the first correct model of DNA.

Watson, Crick, and Wilkin were awarded the Nobel
Peace Prize in 1962. Franklin died of cancer 4 years
earlier.
Joined Nucleotides = GENES

Gene  sequence of DNA that occupies a
specific location on a chromosome and
determines a particular characteristic in an
organism.

Each cell in the human body contains about
25,000 to 35,000 genes

Genes carry information
that determines your traits.
Traits are specific features
you inherit from your parents.
PROTEIN

Groups of 3 nucleotides from a DNA sequence
make AMINO ACIDS
 Ribosomes connect amino acids into long
chains
 Long chains of amino acids = PROTEIN
 Proteins are the building blocks for everything
in your body.
– Bones and teeth, hair and earlobes, muscles and
blood, all are made up of proteins.
– Those proteins help our bodies grow, work properly,
and stay healthy.
CHROMOSOMES
GENES + PROTIENS (built with the ribosomes and
codes of DNA) = CHROMOSOMES

There are hundreds to thousands of genes on
each chromosome

Chromosomes are located in the nucleus of the
cell

Each person has 23 pairs (46 total) of
chromosomes.
– 23 chromosomes come from your father, 23 from your
mother.
The DNA coils
around proteins
made up of amino
acids
DNA
REPLICATION

DNA unwinds.

The original strands serve
as templates for two new
strands.

DNA POLYMERASE
connects to the original
strands and begins to
create new DNA.

Once DNA is replicated, the
chromosome also splits.
MUTATIONS

A mutation is a permanent change in the DNA
sequence of a gene.

Mutations in a gene's DNA sequence can alter
the amino acid sequence of the protein.

Mutations can be positive, negative, or neutral
– EX: Disease, missing body part/function, heightened
senses, bigger and stronger, doubled jointed

Mutations randomly cause adaptations
TYPES OF MUTATIONS

Environmental Factors
– Sunlight (skin cancer, wrinkles, etc),
– Smoking (lung or throat cancer, lung disease, etc)
– Radiation

DNA Replication Error
– Point Mutation
– Frame-shift Mutation
POINT MUTATION

A point mutation is a simple change in one
base of the gene sequence ( A paired with G
instead of T).

This is equivalent to changing one letter in a
sentence, such as this example, where we
change the 'c' in cat to an 'h':
– The fat cat ate the wee rat.
– Point Mutation: The fat hat ate the wee rat.

The gene will now have a mutation, or
change, compared to the original.
FRAME-SHIFT MUTATION

In a frame shift mutation, one or more bases are
inserted or deleted (A, T, C, or G accidentally doesn’t
get copied), the equivalent of adding or removing
letters in a sentence.

Because our amino acids are created from DNA in
three letter "words“ or codes, adding or removing one
letter changes all of the following words.

An example of a frame-shift mutation using our
sample sentence is when the 't' from cat is removed,
but we keep the original letter spacing:
– The fat cat ate the wee rat.
– Frame Shift: The fat caa tet hew eer at.