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

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

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

  3. 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. DNA HOX Gene Click to continue HOX GENES are transcribed into mRNA and then translated by the ribosomes to form HOX PROTEINS. HOX PROTEIN HOX PROTEIN HOX PROTEIN HOX PROTEIN Ribosome HOX PROTEINS then act as regulatory molecules, or TRANSCRIPTION FACTORS, that can promote or inhibit expression of other genes. mRNA mRNA mRNA

  4. 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 PROTEIN • HOX PROTEINS also occur in the cell as REGULATOR MOLECULES. HOX PROTEIN • When the right REGULATOR MOLECULE becomes bound to the right GENETIC SWITCH it can turn a gene ON (promote transcription) or OFF (inhibit transcription) HOX PROTEIN Click to continue RNA pol RNA pol RNA pol RNA pol Genetic switch Genetic switch HOX PROTEIN Genetic switch DNA Promoter Genetic switch Gene (coding DNA)

  5. 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 Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Promoter. Promoter. Promoter. Gene (coding DNA) Gene (coding DNA) Gene (coding DNA) Genetic switch Genetic switch Genetic switch

  6. 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 Click to continue RNA pol RNA pol RNA pol RNA pol RNA pol RNA pol Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch HOX PROTEIN Genetic switch Genetic switch Genetic switch Regulator Regulator DNA Promoter. Promoter. Genetic switch Genetic switch Genetic switch Gene (coding DNA) Gene (coding DNA) mRNA mRNA mRNA

  7. 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 HOX PROTEIN Regulator Regulator Click to continue RNA pol RNA pol RNA pol RNA pol RNA pol Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch Genetic switch DNA Promoter. Promoter. Promoter. Genetic switch Genetic switch Genetic switch Gene (coding DNA) Gene (coding DNA) Gene (coding DNA)

  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. 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: GeneSwitchesOn / Off 1 set of wings Large and flat Has veins No color T2 1 set of haltiers Small and dense Has veins No color T3 1 set of wings Large and flat Has veins Has color scales T2 1 set of wings Large and flat Has veins Has color scales T3

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