3. DNA
Terms:
Chromosome – thread-like
structure made mostly of DNA
Gene – a segment of DNA that
controls protein production
DNA – deoxyribonucleic acid;
material that contains genetic
information; provides instructions
for making protein
5. DNA
Every trait (or characteristic) in your body comes from
instructions from your mother and father
Father Mother
6. Genes
Segments of DNA that
code for specific traits
The instructions are coded in the DNA as genes. Genes
are located in chromosomes.
Gene for height
For example…
Gene for eye-color
This is not an accurate example. It’s just used to illustrate a point.
DNA
7. Father Mother
Chromosomes and their genes are passed to the offspring
(children) through sperm and egg cells (gametes)
Sperm cells
23 chromosomes
Egg cells
23 chromosomes
DNA
8. Father Mother
Chromosomes and their genes are passed to the offspring
(children) through sperm and egg cells (gametes)
DNA
12. DNA
P.A. Levine (biochemist)
determined that DNA was made
up of nucleotides.
-Nucleotides are made up of
1) phosphate
2) ribose sugar
3) nitrogenous base
(nucleotide base)
Nucleotide bases:
-adenine
-thymine
-cytosine
-guanine
13. DNA
Nucleotides are made up of
1) phosphate
2) ribose sugar
3) nitrogenous base
(nucleotide base)
14. DNA
-Other studies confirmed that
nucleotides are joined together
to form long chains.
- Erwin Chargaff found that
there were an equal number of
adenine and thymine as well as
guanine and cytosine.
15. DNA
History
-Not until the 1950s did scientist
discover that DNA carried all the
genetic information. It was
thought that proteins carried the
genetic information.
16. DNA
Alfred Hershey and Martha
Chase Experiment (1952)
-They performed an
experiment using
bacteriophages (viruses
that attack bacteria)
- They wanted to see
whether protein or DNA
held the genetic
information.
17. DNA
Hershey/Chase Experiment
(1952)
Reasoning behind the use of
bacteriophages:
-Bacteriophages were ideal because
they contain both protein and DNA.
-The outer coating of the
bacteriophage is made up of
protein and the inside of the
bacteriophage carries DNA.
- Hershey and Chase devised a way
to mark the protein coat and the
DNA using radioactive sulphur (35
S)
and phosphorus (32
P), so they can
follow what each component did as
the virus attacked the bacteria.
18. DNA
Hershey/Chase Experiment
(1952)
Through their observation, they
noticed that the bacteriophages
DNA moved into the bacterial cells
and directed them to produce new
bacteriophages.
The radioactive protein did not
make its way to the offspring.
The offspring had the radioactive
DNA.
21. DNA
Discovering the Double Helix
Information scientists knew by 1953:
-DNA is made up of nucleotides
-Nucleotides are linked together in a
string.
-In each DNA molecule there is an equal
number of adenine – thymine nucleotides
and an equal number of guanine –
cytosine nucleotides.
QUESTION:
If the nucleotides are strung in a
straight line, a typical DNA molecule
would be over 1 meter long. How is
DNA compressed?
22. DNA
Rosalind Franklin
-photographed molecules using
x-rays (1953). This is what she
observed.
- these patterns indicated DNA
was like a coil. The DNA molecule
had a constant diameter of 2 nm.
It did not get wider or narrower
in some parts of the molecule.
23. DNA
Watson and Crick
-James Watson and Francis Crick
came up with the current model
for DNA in 1953.
-They compared it to a spiral
staircase.
-They called this shape a double
helix.
-They also determined that
nitrogen bases were always
paired in the same manner.
- These paired nitrogen bases are
called complementary base pairs.
27. DNA SCREENING
DNA screening – process of testing individuals for
gene(s) associated with particular genetic disorders.
To test fetuses, cells from the amniotic fluid are extracted
by amniocentesis, and the DNA is examined.
28. Human genetic disorders
Progeria
Physical Effects:
-Premature aging, prematurely
old
-Few exceed 13 years old
-90% die from complications
from atherosclerosis
DNA SCREENING
29. Huntington disease
Physical Effects:
-Progressive brain disorder
causing uncontrolled
movements and loss of
cognition
-May live for 15-20 years after
onset of symptoms
-Trouble eating, swallowing,
talking, etc.
Human genetic disorders
DNA SCREENING
30. Tay Sachs Disease
Physical Effects:
-Nerve cells destroyed in brain
and spinal cord
-Symptoms appear 3-6 months
after birth
-Loss of motor control and
atrophy of muscles, seizures
-Death
Human genetic disorders
DNA SCREENING
32. Albinism
Physical Effects:
-Lack of melanin in skin, hair,
and/or eyes
-May have vision problems
-Sensitivity to UV light
Human genetic disorders
DNA SCREENING
34. Sickle cell anemia
Physical Effects:
-Shortness of breath, fatigue,
delayed growth and
development in children
-May experience painful
episodes of anemia resulting in
organ damage
Human genetic disorders
DNA SCREENING
36. Duchenne muscular
dystrophy
Physical Effects:
-Muscle weakness, delayed
motor development in children
-Wheelchair dependence by
adolescence
-Enlargement and weakening
of the heart
Human genetic disorders
DNA SCREENING
37. Down syndrome
Physical Effects:
-Broad flat face, slanting eyes,
short, growth failure, mental
disabilities, congenital heart disease
-An extra chromosome #21 is
present, totaling 47 chromosomes
Human genetic disorders
DNA SCREENING
40. DNA APPLICATIONS
Genes can also be added to other organisms.
Transgenic organism – organism whose genetic
information has been altered with the insertion of genes
from another species.
