Mutations

• Contrary to what Hollywood would have you believe, a MUTATION is just a change to the genetic code.
• Since the code of life is “written” on DNA in A,T,G and C molecules, think of mutations like a typo.

• Notice that there are no spaces or punctuation between the ATGCs!
• DNA is read in 3 bases sections called CODONS which stand for small proteins called amino acids.
• These amino acids link together to build larger proteins.

• Most mutations are just copying mistakes made by the body.
• Some are caused by environmental things like:
  • Radiation
  • Chemicals
  • Infections

• Sometimes the wrong ATGC is placed when building DNA.
• Notice how the sample sentence changes with a one letter alteration:

Notice how the one letter change results in a different amino acid used in the protein creation.

• Sometimes an extra ATGC or larger piece gets added when building DNA.
• Since DNA is read 3 letters at a time, the entire sequence is shifted:

Insertions can also impact the way proteins are built and can be much larger sections of DNA.

• Sometimes a ATGC or larger piece gets removed when building DNA.
• Since DNA is read 3 letters at a time, the entire sequence is shifted:

Deletions can also impact the way proteins are built and can be much larger sections of DNA.

• Just as some typos cause little difference in the meaning of a word, many mutations don’t cause any change.
• Many of the amino acids used to build proteins have several ATGC sequences so a one letter change still builds the same protein.
  • The amino acid Leucine (LEU) is build using 6 different sequences (TTA, TTG, CTT, CTC, CTA, CTA) so a typo creating one of these synonyms still places the correct link on the protein chain.

• Sometimes different proteins just cause a different trait.
  • The substitution of one letter on human DNA 10,000 years ago resulted reduced melanin protein production in eyes and a new trait of blue!

Blue eyes aren’t good or bad, they’re just different.

• Sometimes different proteins do not build functional structures.
  • These changes are typically considered negative as they result in systems that do not run optimally.

One letter change in blood protein sequence results in misshapen blood cells.

• Cancer is caused by mutation damage to multiple sections of DNA, especially the ones that tell the body to STOP cell growth.
  • Uncontrolled cell growth results in tumors which steal food and spread through the body.

Many changes to specific areas can lead to cancer.

• Sometimes changes to the sequence build way better proteins.
• Much like other animals, ancient humans likely lacked the full spectrum of color vision.
  • Then a mutation that caused new proteins resulted in different eye cells that can see red!
  • Some people still lack this protein and we call that “color-blind”.

It is totally possible that someday someone will be able to see a different color because of a mutation!

• That depends on when they happen and what cells they happen to.
• If mutations happen to or already exist in the sperm and egg cells that carry genetic information, offspring will inherit them.
  • Environmental damage to sperm or eggs.
  • Genetic disorders already on DNA.
• If mutations happen to other body cells, it is unlikely that they will be passed to offspring.
  • Person with lung cancer from smoking won’t pass onto child.