Key Concepts:

1
The DNA Connection

• Key Concepts
• What forms the genetic code?
• How does a cell produce proteins?
• How can mutations affect an organism?
• Key Terms
• Messenger RNA
• Transfer RNA

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The Genetic Code

• Main function of genes is to control the
  production of proteins
• Genes and DNA Chromosomes
• are made of DNA.
• Genes are sections of a DNA molecule that codes
  for one specific protein. May contain several
  hundred to a million or more base pairs (Ex.
  AGGTCACGAATTTTCCGG)

3
Order of Bases

• The order of the nitrogen bases along a gene
  forms a genetic code that specifies what type of
  protein will be produced.
• Proteins are made of amino acids A group of 3
  base pairs codes for a specific amino acid
• Ex. CGT alanine (an amino acid)
• The order of the 3 base code units determines the
  order of the amino acids and makes the different
  proteins

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How Cells Make Proteins(Protein Synthesis)

• The Role of RNA
• Protein synthesis takes place on ribosome in
  cytoplasm
• RNA acts as a messenger to take the DNAs
  information in the chromosomes to the ribosomes
  in the cytoplasm
• RNA similar to DNA, yet different in some key
  ways
• single strand
• ribose sugar
• Bases same - adenine, guanine and cytosine
• different uracil instead of thymine

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Types of RNA

• Messenger RNA copies code from DNA in the
  nucleus and carries message to ribosomes in the
  cytoplasm
• Transfer RNA carries amino acids to ribosome
  and adds them to the growing protein molecule

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Translating the Code

• First Step
• 1. DNA molecule unzips between base pairs
• 2. DNA directs the production of a strand of
  messenger RNA
• 3. To form the RNA strand RNA bases pair with
  DNA bases. Guanine with Cytosine, but uracil
  pairs with adenine instead of Thymine

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Translating the Code

• Second step
• 1. Messenger RNA leaves nucleus and attaches to
  a ribosome in the cytoplasm
• 2. Messenger RNA provides the code to make the
  protein molecule
• 3. The ribosome moves along the messenger RNA
  strand

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Translating the Code

• Third Step
• 1. Molecules of transfer RNA attach to messenger
  RNA
• 2. Bases of transfer RNA read the message by
  pairing up 3-letter codes to bases of messenger
  RNA
• 3. Molecules of transfer RNA carry specific
  amino acids that link in a chain
• 4. Order of amino acids is determined by order
  of 3-letter code on messenger RNA

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Translating the Code

• Fourth Step
• 1. Protein molecule grows longer as each
  transfer RNA adds an amino acid
• 2. When done the transfer RNA is released into
  the cytoplasm and can pick up another amino acid
• 3. Each transfer amino acid picks up the same
  type of amino acid

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Mutations

• A mutation is any change in a gene or chromosome
• Mutations can cause a cell to produce an
  incorrect protein during protein synthesis.
• As a result of a mutation, the organisms trait
  or phenotype, may be different from what it
  normally would have been
• If a mutation is in a body cell, it will not be
  passed on to the offspring. If it is a sex cell,
  it can be passed on and can affect the
  offsprings phenotype

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Substitution
Insertion
Deletion
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Types of Mutations

• Some mutations happen during DNA Replication
• A single base may be substituted for another
• One or more bases may be removed from a section
  of DNA or new bases inserted
• Some mutations happen during Meiosis
• Chromosomes dont separate correctly
• Cell can end up with too many or too few
  chromosomes
• Cell could end up with fragments of chromosomes

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Effects of Mutations

• Mutations introduce change in an organism and so
  are a source of
• genetic variety
• Some mutations are harmful,
• some are helpful, and some dont affect the
  organism
• Whether a mutation is harmful or not depends
  partly on the environment
• A mutation causing an albino animal in the wild
  would be harmful, but if the animal lived in the
  zoo, it would not matter

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Effects of Mutations

• Helpful mutations improve an organisms chances
  for survival and reproduction
• Ex. Bacteria that have mutations that have given
  them resistance to antibiotics are more likely
  to survive and reproduce

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Credits

• http//www.sciencewithmrmilstid.com/media/chromoso
  malDNA.png
• http//www.medceu.com/images/molecularmachine.jpg
• http//www.accessexcellence.org/RC/VL/GG/images/pr
  otein_synthesis.gif
• http//faculty.irsc.edu/FACULTY/TFischer/bio2012
  0files/protein20synthesis20overview.jpg
• http//www.nature.com/scitable/content/ne0000/ne00
  00/ne0000/ne0000/6632005/EssGen_BaseSubstitutionFi
  g1_MID_0.jpg