DNA%20structure%20and%20replication

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DNA structure and replication
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• Where is DNA located in the Cell?
• What do we know about DNA?

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..

• Inside the nucleus of every human cell is nearly
  6 feet of DNA!It can't be crammed into the
  nucleus like a ball of string.
• Instead, it is combined with proteins and
  organized into a precise, compact structure, a
  dense string-like fiber called chromatin

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• Each DNA strand wraps around groups of small
  protein molecules called histones forming a
  series of bead-like structures, called
  nucleosomes,
• Under the microscope, uncondensed chromatin has a
  "beads on a string" appearance.
• This compression and structuring of DNA serves
  several functions. The allows the DNA takes up
  much less space, and inactive DNA can be folded
  into inaccessible locations until it is needed.

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DNA before Replication
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DNA structure

• DNA is made up of many nucleotides connected
  together
• A nucleotide is made of
• Sugar (deoxyribose)
• Phosphate
• Base
• Adenine, Guanine, Thymine or Cytosine

Phosphate
BASE
SUGAR
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DNA structure

• The same bases always connect together
• A T and C G
• The order of the bases give the DNA its
  information or code
• DNA always comes in two strands, like a ladder
  it is called double stranded

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DNA structure

• In 3-D
• DNA winds up in a double helix

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How could you get DNA out of a nucleus?

• How much DNA material could you retrieve from a
  strawberry?
• What would the DNA look like?
• What would you be able to see?

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• Purpose
• Procedure See Hand out
• DataObservations

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Copying DNA DNA replication

• Before the cell divides in Mitosis and Meiosis
  all of the DNA must be copied.
• How?

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Do you remember the basic form of DNA?
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DNA Replication

• DNA needs to replicate itself to create more
  cells.
• Both body cells and sex cells

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Steps to DNA replication

• DNA is unwound and unzipped by enzymes
• The DNA code is read by DNA polymerase (an
  enzyme) which adds the corresponding nucleotide
  (Nitrogenous base, sugar and phosphate)
• Example Adenine is added to Thymine and Cytosine
  is added to Guanine

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DNA before Replication
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(No Transcript)
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Both DNA Strands are read and a new identical DNA
strand is created.

• If the original DNA strand was ATCGCCGTTA The
  corresponding strand created would be TAGCGGCAAT
• What strand would be created if the original
  strand was AAAACCGGATTT?
• The strand would be TTTTGGCCTAAA
• You are so SMART!!!!!!!!!!!

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Lets try a few more What DNA strand would be
created from the following DNA strand?

• AATTACGCGGCCC
• Did you say TTAATGCGCCGGG
• How about TATATACCGATTTA
• Did you say ATATATGGCTAAAT
• Great!!!

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T

• The DNA Polymerase
• serves as a proof reader to correct any mistakes
  that could occur
• Mistakes occur in 1/10,000 nucleotides added. An
  error creating a DNA could cause a disease to
  occur or the wrong directions given in another
  part of the cell.
• Fun Fact some people lack DNA polymerase.
• They are more succeptable to getting cancer when
  DNA is damaged from exposure to UV rays.

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How is the code read in the DNA to create
proteins and give directions other places in the
cell?
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Transcription

• The code to create proteins which lies in the DNA
  must be carried to a place where there are
  materials for the proteins to be created. Where
  are proteins created?
• There is a Problem!!!!
• DNA is copied to mRNA because DNA is too big to
  leave through the nuclear pores.
• It must be changed to something that can fit
  through the nuclear membrane
• mRNA can do the job!!!!

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mRNA is created

• RNA Polymerase opens the DNA molecule
• RNA polymerase looks for a specific code that
  tells it when to start creating mRNA called a
  promoter
• mRNA is created similarly to how DNA is
  replicated except mRNA does not have Thymine.mRNA
  Polymerase adds uracil to the mRNA strand instead
  of thymine to an adenine
• The corresponding Nitrogenous bases are added as
  well as the sugar and phosphate attached.

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Can you break the DNA code?

• If the DNA sequence was ATTCGGCCATT what would
  the mRNA sequence be that was created?
• ___________________________
• Did you say UAAGCCGGUAA
• Yeah!!

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Lets try a few more

• If the DNA sequence was ATTCCGCCGG
• What would the mRNA sequence be?
• Did you say UAAGGCGGCC?
• How about TTCCGCGCGCCGAA?
• Did you say AAGGCGCGCGGCUU
• Great!!!

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Translation when proteins are made from the
mRNAcode

• The mRNA travels to the ribosome where the
  building materials are
• TrNA (Transfer RNA) is great at breaking codes
  in the mRNA to make proteins
• Proteins are made of Amino Acids
• There is a specific code for every three letter
  nitrogenous base sequence in mRNA
• These three letter sequences are called codons.
• Each codon tells which amino acid to add to the
  protein.

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Three letter Codes are Codons.
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For example.

• GUU on mRNA signals a transfer rNA molecule to
  bring Valine a specific type of amino acid.
• If the three letters were GCC the tRNA would
  bring Alanine and add it to the protein.
• Just like building blocks make a wall,Different
  amino acids create a unique protein
• This occurs at the ribosome

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If I gave you the RNA sequence of
CGGGUAUUAUGUGAAUGA what series of Amino Acids
would be created into a protein?
Did you say Arginine,Valine,Leucine, Cytosine and
Glutamine?
YOU ROCK!!!!!
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Lets try one more.. If I gave you the MrNA
strand of CGUAGUAGAAGGGCGUGA what Amino Acids
would you bring together?
Arganine, Serine, Argenine, Argenine,Alanine
FABULOSO!!!!!
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Amino Acids connect to make proteins
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Here is a great picture of the whole process.
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To review, I will give you the player. You will
tell me what is does in the process and where it
hangs out. First for DNA replication

• DNA strand
• DNA polymerase

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Now for transcription and translation

• DNA strand
• Nuclear Membrane
• RNA polymerase
• MrNA
• TrNA
• Amino Acid
• Ribosome
• Codon
• Protein

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Your Job.

• Create 2 comic strips
• 1 comic must illustrate how DNA is created for
  creating new cells
• It must include all major players involved
• They must talk about their role in the process in
  your own words
• They must be pictured in the location they do
  their job.

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The other comic.

• Illustrates transcription (Creation of mRNA) and
  translation (Creation of a protein)
• (How mRNA is created and the code from a DNA
  molecule allows a unique protein to be made)
• This comic must represent each player involved.
• Each player must talk about their individual role
  in the process
• Each player must be located in the environment
  they do their job.

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This will be due.

• Next Friday
• You will have Friday as a work day and some of
  Monday/Tuesday

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Making Copies DNA Replication

• When DNA is copied, the rungs of the ladder break
  right down the middle, and pulls apart.
• 2. A protein DNA polymerase, grabs onto new
  nucleotides and attaches them using the old DNA
  as a template
• 3. New bases are matched to the exposed bases on
  each strand, and the original DNA molecule
  becomes two new identical DNA
• 4. The result is two identical DNA molecules!!