Station 8

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Station 8
Reporting Category 2 Mechanisms of Genetics

• Changes to the Genetic Code

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Essential Question-Bell Ringer

• Humans have approximately 75,000 to 100,000 genes
  in a typical cell. A single gene contains about
  10,000 nitrogen base pairs. How is it possible
  for a single mutation to one of these base pairs
  to cause a life-threatening condition?

Journal
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Essential Question answer Nitrogen base
combinations code for amino acids, which produce
proteins. If a mutation to one of the base pairs
affected a protein that was vital to the
functioning of a crucial organ or system, this
mutation would cause the organ or system to fail.

Journal
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Pre-Review Question

• During the process of protein synthesis, a
  section of the DNA molecule is copied into which
  other molecule?
• Nucleic acid
• Cytoplasmic DNA
• Messenger RNA
• Transfer RNA

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Pre-Review Question

• In messenger RNA, each codon specifies a
  particular
• Nucleotide
• Purine
• Amino acid
• Pyrimidine

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Pre-Review Question

• True or False
• Any change in the genetic sequence (DNA) that
  affects the genetic information is referred to as
  a mutation.
• True

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Pre-Review Question

• Type of mutation that takes place when a base
  codon is changed but both code for the same amino
  acid
• Silent mutation
• Transition mutation
• Transversion
• Deletion

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Lab Activities

• You will now go to the lab and complete the
  activities for todays topics

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Genetic Code Wheel
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1. Using the mRNA Genetic Code chart, determine
the name of the amino acid each codon represents.
Write and answer the question in your journal
(Include the DNA sequences)

• AUG CCA ACA GUG AGA UUA CAG AAA UCG UAA

Start, proline, theorine, valine, arganine,
leucine, glutamine, lysine, serine, stop.
This will serve as your original strand.
2. What does this chain of amino acids represent?
A polypeptide chain or a protein strand.
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Write and answer the question in your journal
(Include the DNA sequences)

• 3. Some genetic mutations are caused by changes
  in the bases of some codons. Compare the two
  sequences below and compare them to the original
  sequence. Can you identify which codon was
  changed and what the new amino acid will be?

• AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA

• AUG CCA ACA GUG AGA UUG CAG AAA UCG UAA

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Answer

• AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA
• Uracil has been replaced with
  cytosine
• This will change the amino acid from valine to
  alanine.

• AUG CCA ACA GUG AGA UUG CAG AAA UCG UAA
• Alanine has been replaced with
  guanine.
• However, this still codes for the same amino
  acide.
• This is known as a silent
  mutation.

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Write and answer the question in your journal
(Include the DNA sequences)
4. If an additional base is added it it called a
frameshift. Compare the original strand to the
strand below and find the insertion. How many
amino acids would be affected?
AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A
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Write and answer the question in your journal
(Include the DNA sequences)
4. If an additional base is added it it called a
frameshift. Compare the original strand to the
strand below and find the insertion. How many
amino acids would be affected?
AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A
Start, proline, theorine, cysteine, glutamic
acid, isoleucine, threonine, glutamic acid,
isoleucine, valine, nothing.
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• 5. What is the significance of this frame-shift
  mutation for the structure of the protein?

After the mutation, 7 of the 10 codons now
code for a different amino acid than the original
sequence did. In addition, a single adenine (A)
base ends the strand. This frame-shift mutation
will cause massive changes in the types of
protein produced by the new strand.
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What I need to remember.
Mutations are changes in DNA that can be
inherited. Certain codons are responsible for
starting the production of a protein, and
other codons stop the process. Mutations
occur when bases are added or deleted and when
segments of DNA are missing. Not all mutations
are harmfulsome are very beneficial.
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Post Review Question

• What type of point mutation is illustrated in the
  table below?
• Substitution
• Silent
• Deletion
• Insertion

Original Strand Mutated Strand
DNA TAC GTA CGG TAA TGC GTA CGG TAA
mRNA AUG CUA GCC AUU ACG CAU GCC AUU
Amino acid Met His Ala Iso Thr His Ala Iso
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Post Review Question

• Identify the following mutation
• Translocation
• Deletion
• Inversion
• Duplication

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Post Review Question

• Identify the following mutation
• Translocation
• Deletion
• Inversion
• Duplication