unit #5 - instructions for life: dnamrpbiology.weebly.com/uploads/2/7/5/6/2756971/dna... · dna dna...
TRANSCRIPT
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Introduction
On the following slides, the blue sections are the most important.
Underline words = vocabulary!
All cells carry instructions for life – DNA.
In this unit, we will study the basic shape of DNA and learn how the molecule DNA carries instructions for life.
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DNA Lab Reflections What did you learn during the
this week’s DNA extraction lab?
What surprised you?
How can this science help
society?
DNA extraction has improved
with modern science. View the
video clip to understand how
crime investigators collect DNA
samples from evidence.
Video
http://flowtv.org/wp-content/uploads/2007/11/csi3.jpg
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DNA – Cell Review
Video
Link
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Instructions Within Cells All cells have genetic
material known as
DNA (deoxyribonucleic
acid).
In prokaryotes, the
DNA is loose within the
cell.
In eukaryotes, DNA is
held within the
nucleus.
Regardless of where the DNA is contained in the cells, the
instructions for every part of an organism come from the
molecule DNA.
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DNA DNA stores and transmits genetic
information from one generation to the
next.
Years of research has
lead scientists to begin to
understand how DNA
works.
DNA is made up of
strings of nucleotides.
Sketch it!
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DNA = Strings of Nucleotides
DNA nucleotides, or
nucleic acids are made
up of 3 basic
components:
– A five-carbon sugar
called deoxyribose
– A phosphate group
– A nitrogen base (A, T,
C, or G)
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Basic Structure of DNA The sugar/phosphate backbone
makes up the outside of the DNA
molecule.
There are four nitrogen bases
that make up the middle of DNA.
They are…
– Adenine: this base always
pairs with thymine
– Guanine: this base always
pairs with cytosine
The bases are connected by a
hydrogen bond.
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Chargaff’s Rules An American biochemist, Erwin Chargaff, studied the
structure of DNA.
Chargaff’s rules state that within the DNA molecule, the percentage (or amount of) of guanine always matches the percentage of cytosine (they always pair together).
Likewise, the %T= %A.
G-CAT rule (straight letters together and curvy letters together)
http://bcs.whfreeman.com/thelifewire/content/chp11/f11005.gif
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Nucleotide Hands
With a pen:
– Write a “P” on
your thumb
– “S” on your palm
– Write an “A” on
your 1st finger
– “G” = 2nd finger
– “C” = 3rd finger
– “T” = pinkie
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1. A’s pair with T’s
2. G’s pair with C’s
3. Sugars with the
Bases
4. Phosphates are free!
Memory
Tool
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DNA Writing Prompt
What is DNA?
Add details to your prompt from
last week:
– The shape?
– The components (or parts)?
– The pattern?
– Draw a picture for extra credit!
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DNA Structure Chart
Backbone Center
Nucleotides
Sugar
Phosphate
Nitrogenous
Base
a a
a X
X X
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DNA’s History:
Franklin’s XRays In the early 1950’s,
Rosalind Franklin (a woman!) studied the structure of DNA using X-rays.
Franklin’s X-rays eventually led to the discovery that the strands of DNA are twisted around each other in a shape much like the coils of a spring, known as a helix.
Video
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Franklin's X-ray
diffraction
photograph of
DNA, 1953
Photo: Courtesy
HarperCollins
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DNA’s History: Watson &
Crick’s Model Around the same time
Franklin was researching DNA, two other scientists James Watson and Francis Crick were also studying DNA.
They built 3-D models to show the shape of DNA using wire and cardboard.
Watson and Crick’s model of DNA was a double helix, where 2 strands of DNA twist around each other.
http://itcamp.teacher.org.hk/2009CU1/GEN5/files/images/dnastructure.jpg
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Reconstruction of Crick
and Watson’s 1953
molecular model of DNA,
using the original
components.
© Science Museum/Science
and Society Picture Library
The Model That Started it All
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DNA Quick Fact
If you took the DNA found in every
cell of the human body and
stretched it out, it would be 610
million km long. You could travel
from Earth to the sun and back –
twice!
http://www.louisville.edu/a-
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Practice Creating the Code
Pick up a white board and marker from the
front.
Practice making the complimentary DNA
strand using the following code.
A G C T A G C
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Practice Creating the Code
Pick up a white board and marker from the
front.
Practice making the complimentary DNA
strand using the following code.
A C T G A T A
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DNA
Replication DNA contains instructions for every cell of an organism.
It, therefore, needs to be copied (or replicated) for each new cell to function properly.
The design of DNA makes it easy to copy!
Using the “G-CAT” rule, half a strand of DNA can easily create the complimentary strand!
DNA replication is when a cell duplicates its DNA.
http://bio.usuhs.mil/dna_replication2.gif
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Replication Fork
During DNA replication, the strand separates into two strands forming a replication fork.
Enzymes (specifically DNA polymerase & helicase) help during replication and unzip the DNA molecule to create the fork.
This can occur spontaneously at multiple points along the DNA strand until the entire strand has been copied.
http://www-
math.mit.edu/~lippert/18.417/lectures/01_Intro/Pictures/100000000000014A0
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DNA Polymerase
DNA polymerase travels down the strand, reading each nitrogen base (A,T,C or G) and using molecules made within the cell, builds the new strand.
Remember, A always with T, C always with G! (G-CAT)
Each DNA molecule to go through replication has one “old” strand and one “new” strand.
Video
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Semi Conservative Model (of
DNA Replication)
The Semi-conservative model of DNA replication statest that each DNA molecule to go through replication has one “old” strand and one “new” strand.
Video
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The Central Dogma
DNA RNA PROTEIN
Replication
Transcription Translation
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Genes Contained with DNA
The DNA within cells
is contained within
chromosomes in the
nucleus.
Sections of the DNA
strand code for
specific information,
called genes.
Genes code for
specific traits (EX
brown eyes, skin color,
or blood type).
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Genes Code for Proteins The genes within a cell’s
DNA code for instructions, but instructions for what?
The instructions in DNA are instructions for making proteins.
Proteins (large molecules) are involved in many biological functions, from making up our skin, hair, and muscles, to fighting the common cold.
DNA makes the proteins that create you! http://images.clinicaltools.com/images/gene/codon.jpg
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RNA
DNA is held within the nucleus of each cell.
mRNA (or messenger ribonucleic acid) carries a copy of the genetic code to make proteins at the ribosomes (rRNA) of the cell.
http://www.biologycorner.com/resources/mRNA-colored.gif
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RNA cont. RNA is composed of:
– sugar called ribose
– a phosphate group
– and nitrogenous base
– “U-A G, C”
– Uracil (replaces Thymine) in RNA
RNA is single stranded, not double like DNA
There are three types of RNA (mRNA, tRNA, and rRNA).
http://www.accessexcellence.org/RC/
VL/GG/images/rna.gif
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Practice Creating the Code
Pick up a white board and marker from the
front.
Practice making the complimentary RNA
strand using the following code.
A C T G A T A
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Practice Creating the Code
Pick up a white board and marker from the
front.
Practice making the complimentary RNA
strand using the following code.
A C T G A T A
U G A C U A U
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Messenger RNA
Messenger (mRNA) is one type of
RNA that carries DNA “message”
out of nucleus to the ribosome.
mRNA is created in the nucleus in
the process called transcription (or
the process of copying genetic
information from DNA into mRNA).
Transcription happens in the
nucleus.
http://www.tokyo-med.ac.jp/genet/mutation/nort.gif
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Making mRNA
If the DNA code reads like this…
ATC-GTA-CGC-AAT-TGC
…Then the mRNA code reads like this…
UAG-CAU-GCG-UUA-ACG
A = U
G = C
The enzyme RNA polymerase separates two strands
of a DNA double helix and builds a strand of RNA
using RNA nucleotides (A, U, C, G).
Remember, RNA is a single strand.
The creation of RNA is called transcription.
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Transfer RNA or tRNA
Transfer (tRNA) RNA carries
amino acids to the ribosome
where the proteins are built.
A tRNA molecule is a single
strand of RNA that loops back
on itself.
One looped end of the tRNA
has a codon that matches the
mRNA codon.
The other end carries an
amino acid. http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/nuclei
c/chpt15/tRNA.gif
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Translation The ribosome is an
organelle in the cell
which builds proteins.
The mRNA carries the
“code” (or instructions)
to the ribosome.
The ribosome reads
the strand three bases
at a time.
Three base pairs
(called a codon or a
triplet; EX “AUG”) code
for a specific amino
acid; amino acids make
up proteins.
http://www.chesterfield.k12.sc.us/Cheraw%20Intermediate/DaveEvans/Biolog
yICP/Protein%20Synthesis.jpg
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Protein Synthesis Video
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RNA Codons Molecules called amino acid chains make up proteins.
Some codons do not code for amino acids, but signal a ribosome to either “start” or “stop” copying the strand.
There is only one “start” codon (AUG) that can begin the process (methionine).
UAA, UAG and UGA are 3 stop codons (like a period at the end of a sentence) which tell the ribosome the protein is complete.
http://genetics.gsk.com/graphics/codon.gif
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AA Chart An amino acid chart
helps to translate codons.
Start at the center and pick a letter.
Move to the next level and pick another letter.
Finally move to the outside and the three letters (a “codon”) match up to an amino acid (found on the outside!).
Practice: GGA codes for….?
http://bioephemera.com/wp-content/uploads/2007/03/image003.jpg
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Translation occurs when the cell uses the genetic information in mRNA to build proteins.
Translation is done at the ribosome (the site of protein synthesis).
mRNA comes from the nucleus and binds to the ribosome.
the “start” codon AUG signals the beginning of a protein.
tRNA molecules carry specific amino acids from around the cytoplasm to the ribosome.
As each tRNA molecule arrives with an amino acid, it links it to the previous amino acid that was dropped off there, forming a long chain.
Translation = Building a Protein
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Protein Synthesis Animation
(a protein)
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Protein Synthesis
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All cells (prokaryotes & eukaryotes) contain DNA!
The role of DNA is like the “master plan” that a builder would use to construct a house.
The role of RNA is like the inexpensive blueprints that are taken to the construction site (mRNA & tRNA).
The DNA (master plan) must be stored safely in the nucleus while RNA can leave the nucleus to go to the protein-building site.
The protein building site is the ribosome.
In Conclusion
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