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DNA: Blueprint for Life
DNA is
a long molecule called
Deoxyribonucleic Acid
DNA is a
code
There are 2 types of code. The
first type is:
 a set of symbols used to
communicate
Examples of codes:
The
English
alphabet
Hebrew alphabet
Greek
alphabet
Russian
(Cyrillic)
alphabet
Chinese alphabet
Arabic
alphabet
Egyptian Hieroglyphics
Mathematics
π
0
1
2
3
4
5
6
7
8
9
Morse
Code
bar codes
Music
Body Language
Braille
Sign Language
Referee Signals
International Signs
Company Logos
Codes can also be:
password
 a set of instructions
Pollard Code
of Conduct
dress code
Lego
instructions
zip code
02492
telephone
number
computer code
locker
combination
blueprints
origami
DNA
is both
 a set of symbols used to
communicate
AND
 a set of instructions
DNA
DNA is a gigantic molecule made up of millions
of these smaller molecules:
Sugar(deoxyribos
e)
Nitrogen bases
Adenine (A)
Thymine (T)
Guanine (G)
(C)
Cytosine (C)
A nucleotide is the “building block” of the
DNA strand. It contains:
• 1 sugar
P
nitrogen
• 1 phosphate
• 1 nitrogen base
(either Adenine, Cytosine,
Guanine or Thymine)
The DNA molecule’s
shape is a twisted
ladder, or double helix.
S
NB
Nucleotide
P
S
Sugar phosphate
backbone
NB
Millions of
nucleotides
bond together
to form a DNA
molecule.
The shape of the DNA molecule is
a double helix, or twisted ladder.
See how the DNA molecule looks like a ladder?
DNA “Ladder”
The sugar and
phosphate molecules
form the sides or
backbone of the ladder.
C
P
The DNA molecule is
held together in the
middle by weak
hydrogen bonds
between the nitrogen
base pairs.
DNA structure
S
S
P
T
P
The nitrogen bases
form the “rungs” of the
ladder.
G
A
S
S
P
G
P
C
S
S
P
A
P
T
S
S
P
C
P
G
S
S
P
A
P
S
T
S
P
4 different bases
C
CYTOSINE
A
ADENINE
G
GUANINE
T
THYMINE
Guanine only
bonds with
Cytosine
DNA Structure
Adenine only
bonds with
Thymine
What’s Where?
What’s Where?
cell
nucleus
chromosome
gene
Chromosomes, Genes and DNA
Diagram and photograph
of a chromosome.
Human chromosome set
from a skin cell.
• Chromosomes are long strands of DNA.
• Humans have 46 chromosomes in every body
cell.
• Genes are sections of chromosomes. Humans
have around 25,000 genes in every cell.
DNA SONG
We love DNA
Made of nucleotides,
Sugar, phosphate, and a base
Bonded down the sides.
Adenine and thymine
Make a lovely pair.
Cytosine without guanine
Would feel very bare.
Oh-h-h, de-ox-y-ri-bo
Nu-u-cle-ic acid.
DNA Song #2
RNA is ri-i-bo
Nu-u-cle-ic acid.
DNA Rap
Winners of the Race to Learn DNA’s Structure -Watson and Crick
in 1953
with
their model of DNA
Watson
and
Crick
Bob Watson
Francis Crick
Rosalind Franklin
Rosalind Franklin was a young British scientist whose
experiments in X-ray crystallography at King’s College
London were essential to the discovery of DNA’s double helix
shape by James Watson and Francis Crick in 1953. Franklin
was cheated of deserved recognition by her early death from
cancer, at the age of 38, in 1958. Nobel prizes are never
awarded posthumously; when Watson, Crick and Wilkins got
their awards in 1962, she was therefore ineligible, even though
Watson & Crick owed much of their success to her work.
Some fascinating facts about DNA…
 a single DNA molecule is made of 240 billion
atoms (a water molecule is made of 3 atoms).
 Each chromosome is a single DNA molecule
about 2 inches long.
 If you unraveled all the DNA is one cell, it
would measure 7 to 8 feet.
 99.9% of all human DNA is the same; only
0.1% is different in each person.
 There are 3 billion nitrogen base pairs in
one DNA molecule.
DNA Replication
Step 1
The DNA molecule
“unzips” down the middle.
Step 2
Unattached nucleotides,
floating in the nucleus,
attach themselves to the
two “half-ladders”,
making….
Step 3
2 identical DNA molecules
DNA Replication
1) The DNA unwinds and separates
down the middle (“unzips”)
2) Nucleotides floating in the
nucleus attach to the 2 open
sides. A -- T, C -- G
3) There are now 2 identical DNA
molecules.
Protein Synthesis
 The nitrogen bases (A, G, C, T) make up DNA’s
code. The bases are read in groups of 3.
 A group of 3 bases is called a codon.
 Each codon
stands for 1 of
the 20 amino
acids.
There are also
codes for “Stop”.
Amino Acids
• Amino acids are the building
blocks of proteins.
• A protein is a large molecule
made of many amino acids bonded
together in a certain order.
• Proteins:
 carry out all cell functions
 give an organism its traits.
Amino Acid
Alanine (ala)
Arginine (arg)
Asparagine (asp)
Aspartic Acid (asa)
Cysteine (cys)
Glutamic Acid (glu)
Glutamine (gin)
Glycine (gly)
Histidine (his)
Isoleucine (ile)
Leucine (leu)
Lysine (lys)
Methionine (met)
Phenylalanine (phe)
Proline (pro)
Serine (ser)
Threonine (thr)
Tryptophan (trp)
Tyrosine (try)
Valine (val)
Stop codons
A picture is worth a 1000 words….
DNA
Bases
Base
G
C
A
A
G
T
A
C
C
T
G
A
A
C
C
T
G
A
T
pairs
G
Codons
Amino
Amino
acids
acids
G
C
A
A
G
T
codon
codon
codon
codon
amino acid
amino acid
amino acid
amino acid
amino acid
amino acid
amino acid
Protein
amino acid
Some
Genetics
Numbers
Some
Genetics Numbers
in one human cell
in one human cell
there are…
there are…
3 billion base pairs
3 billion base pairs
1 billion codons
1 billion codons
25, 000 genes
25, 000 genes
46 chromosomes
46 chromosomes
7 feet of DNA
7 feet of DNA
Number of people on Earth: 6.6 billion
Number of people on Earth: 7.05 billion
Number of people with exactly your DNA ….1
Number of people with exactly your DNA ….1
YOU !!!
YOU !!!
GENES BY THE NUMBERS
Even though all the cells in the body contain the exact same
genes, the genes that are “turned on” in each cell vary
depending on the cell’s function. These are the numbers of
working genes in different parts of the body.
Brain
3195
White blood cell
2164
Liver
2091
Heart
1195
Pancreas
1094
Bone
904
Colon
879
Skeletal muscle
735
Kidney
712
Skin
629
Thyroid Gland
584
Eye
547
Small Intestine
297
Smooth muscle
127
Esophagus
76
Red blood cell
8
Mutation
Accidents Happen, With Some
“Accidents” (Base Mismatches) Leading
to Mutation
A mutation is a change in DNA sequence.
Mutations due to replication errors only happen
once in every trillion replicated nucleotides.
There are 3 types of base-pair
mutation:
1. A base pair is dropped (DELETION)
Example:
CCCTTT becomes CC TTT
Base-pair mutations
2. A base pair is added (INSERTION)
Example: CCCTTT becomes CCCGTTT
Base-pair mutations
3. A base pair is switched (SUBSTITUTION)
Example: CCCTTT becomes CCATTT
Hemoglobin mutation
A substitution
in one base
causes a
change in one
amino acid,
which
changes the
hemoglobin
protein
enough to
cause sickle
cell anemia.
Mutations
• Mutations happen all the time, in every species.
• Mutations are usually harmful or neutral --mutations are rarely beneficial.
• Mutations can cause cancer & some diseases
(bad).
• Mutations are the only way to bring new genes
(traits) into a species (good for evolution).
So, just like Goldilocks – not too
hot, not too cold, just right – the
optimal rate of new mutation is
a balancing act.
Causes of Mutation
Environmental factors such as
1.UV (ultraviolet) light (sunshine)
2.nuclear radiation
3.certain chemicals
Biohazard (mutagenic
chemicals)
4. Copying errors
Mistakes during DNA replication
Nuclear radiation
Chromosomal Alterations
Sometimes mutations occur to an entire
chromosome, affecting the structure of the
chromosome.
Chromosomal Alterations
Sometimes mutations affect the number of
chromosomes (an entire chromosome is missing, or
there is an extra chromosome).
Down syndrome, or
Trisomy 21
Patau syndrome, or
Trisomy 13
Mitochondrial DNA
Did you know that, in addition
to the DNA in the cell nucleus,
your cells also have DNA in
their mitochondria?
Mitochondrial DNA
• 37 genes
• inherited from your mother, since usually only
the egg contains mitochondria (the sperm’s
mitochondria are in its tail, which falls off after fertilization)
•13 of the genes give instructions for cellular
respiration
• the rest give instructions for making transfer
RNA (tRNA) and ribosomal RNA (rRNA)
Mitochondrial DNA
DNA in chloroplasts
chloroplast
Chloroplast
genome in a
liverwort
Learn more about it
DNA in a chloroplast
karyotype
Karyotype: a picture of all 46 of a person’s
chromosomes, arranged in 23 pairs.
However, the 23rd
pair of
chromosomes do
not look alike at
all.
Note that 22 of
the 23 pairs of
chromosomes
are the same
size, and have
the same
banding
patterns.
The first 22 pairs
of chromosomes
are called
“autosomal.”
The 23rd pair of
chromosomes are
called the sex
chromosomes, or
X and Y
chromosomes.
Make a karyotype
How scientists read chromosomes
X and Y Chromosomes
The 23rd pair of chromosomes in
humans determines a person’s
gender.
A female has two X chromosomes;
a male has 1 X and 1 Y chromosome.
Female: XX
Male: XY
X chromosome is much larger than the Y chromosome.
Gender Determination
egg
girl
X
X
boy
Y
Which of these
karyotypes
shows a male,
and which shows
a female?
A
B
Genetic abnormalities of the XY
Chromosomes
Klinefelter
Syndrome
XYY syndrome
Triple X
syndrome
Turner
Syndrome