The Secret Code of Life:

1. The Secret Code of Life: “The Cellville Cipher”

2. Codes and Ciphers: • The Pigpen code will work to encode secret messages only if the other person receiving the message knows the key • Codes were made as a means of sending information easily such as the Morse code, or to send secret information – short and secret • A code replaces words, phrases or sentences with numbers or letters while a cipher rearranges the letters to further disguise the message

3. Can you decipher this? Can you decode this message? • There are no secrets better kept than the secrets that everybody guesses." • This is the pigpen cipher, an original French cipher, that was used by groups such as Napolean’s spies to send secret messages

4. Why does the human body need a code? • The nucleus has an amazing design of sending information quickly to the rest of the cell (function is to control the cells functions) • The nucleus houses the DNA which owns the genetic code. • The stored information in the DNA needs to transfer it’s information quickly and reliably into a product. The information is stored in packets or “files” called genes. • Genes are places or locations on a chromosome that contain a specific piece of information for the creation of a protein. The transfer of this information is called PROTEIN SYNTHESIS.

5. The Central Dogma • The central dogma or “idea” of the transmission of information in the cell is: • Transcription Translation • DNA  RNA  PROTEIN • Where, DNA is read and transfers the information of the blueprint of the protein to RNA, and RNA transfers this information to be created in the cytoplasm • Transcription + Translation = Protein Synthesis • On your worksheets, which represents the RNA? Which represents the protein?

6. The Genetic Code • The DNA has a triplet code using only the 4 nucleotides, A,C,G and T. Only 3 nucleotides form a triplet which, when in a gene, codes for a part of a protein. • There are 34 total different triplets that can be created but only 20 different amino acids. (Would a doublet code work just as well?? i.e. only 2 nucleotides to represent 20 amino acids. Why are there a lot of codes that mean the same amino acid?) • Many triplets in a specific order will generate a specific protein (this is based on the order of the bases in the DNA) • The bottom line is that the genes we have in our DNA create PROTEINS which we need. • These proteins are made up of amino acids joined together in a specific manner to create the protein needed. • There are 3 stop codons which tell the machinery not to continue the protein synthesis process.

7. TAC GCT TAA CGG ACT TTA ATG CGA ATT GCC TGA AAT AUG CGA AUU GCC UGA Met – Arg – Ile – Ala – stop DNA STRANDS mRNA Protein Example

8. MUTATIONS – When the code is changed! • A mutation is a change in the DNA from its original form (mutatio = change, alteration in Latin) • When just one base is changed in the DNA, it is considered a mutation. It would also create a new allele for the gene. Not all mutations are harmful.

9. Types of Mutations • A. Chromosomal Mutations • Aneuploidy or a loss or gain of a whole chromosome: occurs when mitosis or meiosis doesn’t function correctly and causes a cell to have 46 +/or- 1 or 2 chromosomes e.g. X0 = Turner’s syndrome • Polyploidy or a loss or gain of a whole set of chromosomes: instead of having 46 chromosomes, an additional 23 chromosomes are added or 23 are lost! (not found in humans but can occur in plants!!) • Loss of a part of an arm of a chromosome = translocation. This occurs when the arm of one chromosome is attached to a different chromosome. (Could be reciprocal where both arms are attached to the other recipient chromosome) • Inversions: where a portion of a chromosome rearranges the order of the DNA inside the arm • Deletions: a large piece of DNA is taken out of the chromosome • Duplication: a large segment of DNA is copied and inserted beside its original sequence. • Insertion: a large piece of DNA coming from one chromosome and put into another

10. B. Point Mutations i) Insertion: 1 or 2 bases are added to DNA at one place (not in multiples of 3 – why is that?) These mutations can cause serious effects if it occurs within a gene as the triplet sequence will be disrupted ii) Deletion: 1 or 2 bases are deleted to DNA at one place (not in multiples of 3 – why is that?) These mutations can cause serious effects as well if it occurs within a gene as the triplet sequence is disrupted Iii) Substitution: of 1 base for another base e.g. A  T or G  C These mutations may or may not be harmful depending on where the change in the gene occurs and the effect of this change on the resulting amino acid that it is changed to. i)TAC GCT AGG ATG TAC GGC TAG GAT G ii) TAC GCT AGG ATG TAC CTA GGA TG iii)TAC GCT AGG ATG TAC ACT AGG ATG Types of Mutations

11. Effects of mutations on Proteins • Positive – causes the protein to be have an even better function/ does its job better (this will allow for natural selection and evolution) • Negative – causes the protein to have little or no function OR disrupts another protein’s function e.g. Sickle cell anemia • Neutral – causes the protein to have no significant change in function (many are in this category such that we never see disease from these mutations)

12. Effects of DNA changes on Proteins A. Normal protein B. Neutral mutation No change in the active site D. Positive mutation C. Negative mutation No active sites 2 active sites now, more effective protein

13. Bibliography and Credits http://www.nationalarchives.gov.uk/online/spies/codemaster/default.asp http://www.accessexcellence.org/AB/GG/mutation2.html http://www.people.virginia.edu/~rjh9u/code.html http://www.nationalarchives.gov.uk/online/spies/codemaster/default.asp http://www.accessexcellence.org/AB/GG/dna2.html http://www.accessexcellence.org/AB/GG/mRNA.html