The Wonderful World of DNA

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The Wonderful World of DNA

• (Deoxyribonucleic Acid)

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Review

• Everything is made of matter
• Matter is made of molecules
• Molecules are made from elements
• DNA is a molecule that is made from other
  molecules

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What does it look like
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DNA Fun Facts

• DNA was first isolated in 1869 by Friedrich
  Miescher.
• James Watson and Francis Crick figured out the
  structure of DNA in 1953. Although they did
  borrow much of the research to figure it out.
• DNA is a double helix.
• One chromosome can have as little as 50 million
  base pairs or as much as 250 million base pairs.
• If unwound and tied together, the strands of DNA
  in one cell would stretch almost six feet but
  would be only 50 trillionths of an inch wide.
• Over 99 of our DNA sequence is the same as other
  humans

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DNA is important because

1. It has a really long, scientific name
2. It is the instructions that code for the creation
   and maintenance of living things
3. It is what mitosis uses for its phases
4. All of the above makes DNA important

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A double helix is like a

1. Spiral Staircase
2. A twisted ladder
3. A piece of licorice
4. More than one of the above are correct

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The DNA model

• It all starts with the backbone
• A Phosphate is connected to the deoxyribose sugar
• The bonds holding them together are STRONG.
• We dont want the DNA to separate along backbone

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The DNA model

• The building block is a nucleotide
• DNA is built from small similar parts called
  nucleotides
• It consists of three parts
• A phosphate
• Connected to the Sugar
• A nitrogen base connected to the sugar
• There are 4 nitrogen bases Adenine, Thymine,
  Guanine and Cytosine
• They pair up on opposite sides of the DNA
• Adenine with Thymine Cytosine with Guanine

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DNA has two backbones.

1. True
2. False

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Nitrogen bases in DNA pair up like this

1. A C, G - T
2. G A, T - G
3. A T, G - C
4. They dont pair up at all

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A nucleotide is like

1. A lego
2. A brick
3. A puzzle piece
4. All of the above

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A little video clip showing this DNA Stuff
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The Code

• The A, T, G Cs are set in an order for a
  specific trait
• The code can only be read when the DNA is open
• It is coded in 3 letter sequences.
• Each 3 letter sequence is called a CODON.

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Which would be an example of a codon?

1. CBA
2. GATTACA
3. KFAN
4. None of the above

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Reading the Code

• When DNA is read, it is read one gene at a time
• Each gene codes for a specific trait
• When a gene is ready to be read, DNA unzips
• A molecule called mRNA is formed as a copy of the
  code

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mRNA

• mRNA (messenger RNA)
• Made with Ribose sugar instead of Deoxyribose
• Only a single strand, but still twisted
• Uses Uracil as a nitrogen base instead of Thymine
• Built as a match to DNA

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Reading the code

• Each codon is represented by one AMINO ACID.
• Amino Acids are assembled in the order of the
  code.
• When assembled they are called PROTEINS.

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We still havent said how the code is read!?

• The actual reading is done by the RIBOSOMES
  outside of the nucleus.
• They call for molecules call tRNA that carry
  specific amino acids
• The tRNAs bring in the aminos and attach them to
  the ones that are there, creating a long line of
  amino acids call a PROTEIN.

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tRNA

• tRNA (transfer RNA)
• Is a short strand of RNA
• Only 3 nucleotides long (1 codon)
• Carry one specific amino acid that is specific to
  the code that it has

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The Process is in Two Stages

• Stage 1 (Transcription)
• DNA unzips
• mRNA is made
• mRNA is released into nucleus
• DNA zips back up

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What is created in the end of transcription?

1. 2nd half of DNA
2. tRNA
3. Unzipped DNA
4. mRNA
5. None of the above

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Transcription Video
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• Stage 2 (Translation)
• mRNA goes out of the nucleus
• Attaches to a ribosome at one codon
• Ribosomes read the code and call for one of the
  tRNAs with the opposite code
• tRNA matches up with the mRNA at the ribosome,
  attaches its amino acid to the others that are
  there (peptide bond between aminos), then leaves
• Continues to do this until the mRNA runs out
• mRNA returns to the nucleus and breaks up into
  its nucleotides.
• The amino acid chain is the PROTEIN (or a
  polypeptide) and is released to control the trait

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What is created in the end of translation?

1. Protein
2. tRNA
3. Unzipped DNA
4. mRNA
5. None of the above

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Translation Video
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Amino Acid Table
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(No Transcript)