1. Click to continue How do a few genes build a diversity of body parts? There’s more in the genetic toolkit than just genes! Click your forward cursor to see how it works… The Tools GENES HOX GENES REGULATORY MOLECULES (Hox Proteins) PROMOTOR REGIONS of DNA GENETIC SWITCHES

2. Gene (coding DNA) DNA Turns out it takes more than just a GENE to build a body ~ 98% of DNA is non-coding Junk DNA~ 2% of DNA contains all the GENES And not everything outside the coding genes is junk DNA X Promoter PROMOTER REGIONS are associated with genes and help initialize transcription of the gene into a protein Genetic switch Genetic switch Genetic switch Genetic switch GENETIC SWITCHES play a role regulating the EXPRESSION of genes Click to continue

3. HOX Gene DNA mRNA Ribosome HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX GENES are an important set of genes in most animals. They are part of the genetic tool box that regulates development of an organism. HOX GENES are transcribed into mRNA and then translated by the ribosomes to form HOX PROTEINS. HOX PROTEINS then act as regulatory molecules, or TRANSCRIPTION FACTORS, that can promote or inhibit expression of other genes. Click to continue

4. HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN Gene (coding DNA) Promoter Genetic switch DNA RNA pol Genetic switch Genetic switch Genetic switch RNA pol RNA POLYMERASE is an enzyme in the cell It is essential in making mRNA to translate into the amino acid sequence to form protein HOX PROTEINS also occur in the cell as REGULATOR MOLECULES. When the right REGULATOR MOLECULE becomes bound to the right GENETIC SWITCH it can turn a gene ON (promote transcription) or OFF (inhibit transcription) Click to continue

5. Gene (coding DNA) Promoter. Genetic switch Genetic switch Genetic switch Genetic switch Gene (coding DNA) Promoter. Genetic switch Genetic switch Genetic switch Genetic switch Gene (coding DNA) Promoter. Genetic switch Genetic switch Genetic switch Genetic switch BUT… Even though every cell in the body contains the exact same DNA with the same GENES Not every cell contains all the same REGULATORY MOLECULES So only certain GENES might be turned on, or EXPRESSED, in certain types of cells Click to continue

6. Gene (coding DNA) Promoter. Genetic switch DNA Regulator RNA pol Genetic switch Genetic switch Genetic switch RNA pol In the right type of cell… With the right REGULATORY MOLECULE To bind to the right GENETIC SWITCH A GENE can be turned ON In this case the regulator helps bring an RNA POLYMERASE to the PROMOTOR REGION to initialize mRNA transcription The gene is EXPRESSED RNA pol Genetic switch Regulator Genetic switch Genetic switch Genetic switch RNA pol Gene (coding DNA) Promoter. Genetic switch Genetic switch Genetic switch Genetic switch HOX PROTEIN Click to continue mRNA

7. Gene (coding DNA) Promoter. Genetic switch DNA RNA pol Genetic switch Genetic switch Genetic switch RNA pol Regulator Gene (coding DNA) Promoter. Genetic switch Genetic switch Genetic switch Genetic switch Regulator Gene (coding DNA) Promoter. Genetic switch Genetic switch HOX PROTEIN Genetic switch Genetic switch In the right type of cell… With the right REGULATORY MOLECULE To bind to the right GENETIC SWITCH OR… With a different type of switch A GENE can be turned OFF In this case the regulator inhibits the action of RNA POLYMERASE The gene is NOT EXPRESSED RNA pol Click to continue

8. Now on to the rest of the exercise… You’ll have a chance to try your hand at regulating some gene expression in arthropods!

9. 1 set of wings Large and flat Has veins No color 1 set of wings Large and flat Has veins Has color scales 1 set of haltiers Small and dense Has veins No color 1 set of wings Large and flat Has veins Has color scales Now that you understand the regulatory system that controls how genes are expressed, revisit the example of wing differentiation between Drosophila and Butterflies. Explain the genes and regulatory elements involved in the development of these wings: T2 T3 T2 T3 Gene Switches On / Off