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Genes and DNA
Chapter 6
DNA Fun Facts…
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Nearly 6 feet of DNA strands are located in
the nucleus of every cell in your body
We have over 3 billion base pairs in our DNA
Every person’s DNA is 99.99% similar to that
of another person
It is estimated that 98.5% of the chimpanzee
genome is the same as the human genome.
Sec. 1: What does DNA look
like?
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Goals:
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List 3 important events that led to
understanding the structure of DNA
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Describe the basic structure of DNA
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Explain how DNA can be copied
Important People in DNA’s
Amount of
discovery….
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A=T, G=C
1…Erwin Chargaff
•Chargaff’s rules!
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2…Rosalind Franklin
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3…James Watson and Francis Crick
•She discovered the shape of
DNA using X-rays
•Built the 1st model of
DNA
DNA
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Short for “deoxyribonucleic acid”
Is a large chemical molecule that
resembles a twisted ladder
Contains all the genes that determine
the traits of an organism
Found inside every living cell on Earth
DNA contains the following:
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Four Bases (these make the ladder
rungs)
A=adenine, T=thymine, G=guanine,
C=cytosine
Sugar and Phosphate (make the sides)
( Sides are also called the backbone )
Bases are complementary:
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A always pairs with T
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G always pairs with C
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Therefore….CCTAG complementary
to GGATC
Nucleotides
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They are the subunits of DNA
They contain a sugar, phosphate, and
one of the 4 bases:
Genome:
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the genome is the entirety of an
organism's hereditary information
DNA’s Shape:
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Double helix
Tap for
Brainpop !
When copies are made…
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DNA is copied every time a cell divides.
Each new cell gets a copy of
DNA
all the
Making Copies of DNA:
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Replicate: this means making copies
Each base only pairs with one other
base:
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A-T
C-G
This means each side of the DNA strand
is complementary
Write the complimentary
strand:
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ATCGTTAGGCT
How copies are made:
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During replication, the DNA molecule
splits (unzips) down the middle where
the bases meet
As the bases on the original molecule
are exposed, complementary
nucleotides are added to each side of
the ladder
“see diagram next slide”
Tap for animation
Each half of the
molecule is old
DNA,
and half is new
DNA:
Nucleotides come from a variety of
sources, but primarily from the foods
you eat. Animals and plants also
have genomes, do not forget. So,
when you eat vegetables or any kind
of meat or fruit, you're also ingesting
that organism's genome. So, your
body metabolizes all these things,
along with proteins, lipids, carbs, etc.
So, the nucleic acids are metabolized
and broken down into nucleotide
bases. These can then be used to
replicate your own genome.
Additionally, some of your own cells
that die will release their genomes,
and the nucleotides in these can be
recycled.
Sec. 2: How DNA Works
It is the
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of nucleotides that creates the code of
life.
One half strand of DNA has a
complementary half and the sequence
is preserved.
The bases in DNA:
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The bases read like a book.
A, G, T, C form the alphabet of the code.
Groups of THREE bases code for a specific
amino acid.
Strings of these amino acids make up
proteins.
Each gene is a set of instructions for
making a protein.
The big idea:
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Gene’s Sequences of A’s,
G’s, T’s, and C’s tell the cell
what Protein to make.
Proteins:
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Are everywhere in cells.
Act as chemical messengers.
Are the reason living things look so
differently from each other.
1.Enzymes are proteins. Enzymes catalyze chemical reactions
- helping reactions happen as needed.
2. Proteins are structural elements of organisms.
3. Proteins make up parts such as hair, horns, hooves, nails,
...
4. Proteins are integral parts of membranes, helping to
transport materials and acting in cell recognition.
5. The cytoskeleton that gives cells shape and support are
made of protein, as well as the spindle fibers, cilia, flagella,
centrioles, ...
6. Proteins carry oxygen, give immunity, contract muscles, ..
Genes Make Proteins (which
are made up of amino acids):
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1. A copy of a portion of DNA is made and
transferred out to the cytoplasm
This copy is called mRNA (messenger
RNA)
2. The copy is fed through a ribosome,
three bases at a time
3. Transfer molecules feed the correct amino
acid to the ribosome
4. Amino acids are dropped off and joined
together to make the correct protein
•arginine - arg - R (
•asparagine asn - N (gif, interactive)
•aspartic acid - asp - D (gif, interactive)
•cysteine - cys - C (gif, interactive)
•glutamine - gln - Q (gif, interactive)
•glutamic acid - glu - E (gif, interactive)
•alanine - ala - A (gif, interactive)
•glycine - gly - G (gif, interactive)
•histidine - his - H (gif, interactive)
•isoleucine - ile - I (gif, interactive)
•leucine - leu - L (gif, interactive)
•lysine - lys - K (gif, interactive)
•methionine - met - M (gif, interactive)
•phenylalanine - phe - F (gif, interactive)
•proline - pro - P (gif, interactive)
•serine - ser - S (gif, interactive)
•threonine - thr - T (gif, interactive)
•tryptophan - trp - W (gif, interactive)
•tyrosine - tyr - Y (gif, interactive)
•valine - val
Watch the “Gene Scene” !
Genome:
the genome is the entirety of
an organism's hereditary
information. It is encoded either
in DNA or, for many types of
virus, in RNA.
Human genome analogy:
An analogy to the human genome stored on DNA is that of
instructions stored in a library:
•The library would contain 46 books (chromosomes)
•The books range in size from 400 to 3340 pages (genes)
•which is 48 to 250 million letters (A,C,G,T) per book.
•Hence the library contains over six billion letters total;
•The library fits into a cell nucleus the size of a pinpoint;
•A copy of the library (all 46 books) is contained in almost every
cell of our body.
Gene therapy and colorblindness video
DNA
Song!
http:/
/www
.yout
ube.c
om/w
atch?
v=FU
A6_U
cw3i4
Changes in Genes:
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When there is a change in the order of
bases in an organism’s DNA it is called a
Three Types of Changes in
Genes:
1. Substitution: Base pair
replaced
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Ex.
2. Base pair added: Insertion:
Ex.
3. Base pair removed:
Deletion
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Ex.
Genetic disorder: Sickle Cell
Anemia
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Happens with red blood cells
GAA changed to GTA
This substitution makes red blood cells
that have a distorted shape:
Mutation can result in:
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1. A genetic disorder (possible death)
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2. An improvement
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3. No change at all
Big Deal?
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Cells do make special proteins to detect
errors in DNA (DNA police!)
When an error is found, it is usually
fixed
(but not always)
Correct
sequence
stolen!
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Things that can cause a mutation in
DNA
Examples:
UV radiation, excess of X-Rays,
asbestos ( see next slide!), chemicals
in cigarette smoke
ASBESTOS:
Wrapped around
a pipe
In the ground
Why was it used?
From the time that asbestos was discovered in the first
century, its properties amazed people. It had the ability to
protect from heat, flames, noise and condensation. In fact,
early Greeks used it for both lamp wicks and clothing.
By the 1800s, asbestos was considered to be even more of a
“miracle mineral” and was used in conjunction with the growth
in industry. Using this readily available and inexpensive
material in all manners of household construction offered
many benefits, with no visible drawbacks, at the time. Asbestos
could be used to fill spaces, cover items, mix with liquids or
combine with paints. It could keep flames lit, heat in, cold out,
sound clear, damp areas dry and cement strong. In fact, by the
1970s it seemed that mankind was still discovering uses for
asbestos. It was put into paints, adhesives, clay, crayons,
protective wear, metal ware and, of course, appliances. With its
adaptability, it seemed to meet countless needs in different
ways.
Genetic Engineering
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Transfer genes from one organism to
another:
Human milk gene in cow
Firefly gene in a plant
Genetic Identification:
Identifies unique patterns in an individual’s DNA