1. GENE EXPRESSION HOW DOES DNA KNOW WHEN TO MAKE A PROTEIN?

2. DNA and Individuality Are all genes turned on in all cells?

3. The answer is NO! Every body cell contains all DNAEvery body cell contains all DNA Cells “use” only genes specific for functionCells “use” only genes specific for function –EX. Red blood cells use only genes that make it carry oxygen –Can you list more examples? Skin cells only need proteins for structure and suchSkin cells only need proteins for structure and such Nerve cells only need proteins that enable them to transmit impulsesNerve cells only need proteins that enable them to transmit impulses **THEREFORE, NOT ALL DNA IS EXPRESSED (MADE INTO PROTEIN) IN EVERY CELL!**

4. MUTATIONS When DNA goes bad 

5. IMPORTANT FACT! MUTATIONS MUST OCCUR IN SEX CELLS IN ORDER FOR THEM TO BE PASSED ON TO NEXT GENERATION!!!!!!!!!!

6. I REPEAT……………… ONLY MUTATIONS THAT OCCUR IN EGG OR SPERM CELLS CAN BE PASSED ON TO OFFSPRING!! ONLY MUTATIONS THAT OCCUR IN EGG OR SPERM CELLS CAN BE PASSED ON TO OFFSPRING!! (Have you ever heard of a sperm fertilizing a skin cell to make a baby?? That is silly!)

7. Chromosomal Mutations Change in # of chromosomes or structureChange in # of chromosomes or structure –EX: NORMAL HUMAN BODY CELL = 46 Let’s see this!NORMAL HUMAN BODY CELL = 46 Let’s see this!Let’s see this!Let’s see this! DOWN’S SYNDROME CELL = 47DOWN’S SYNDROME CELL = 47 Let’s see this! Let’s see this!Let’s see this!Let’s see this!

8. Gene Mutations Change in actual DNA sequenceChange in actual DNA sequence **Review** What does DNA ultimately code for?**Review** What does DNA ultimately code for?Proteins Is construction of protein based on original DNA strand?Is construction of protein based on original DNA strand? Yes! (b/c it is what codes for mRNA)

9. Gene Mutations con’t… What would happen to protein made if DNA sequence was changed?What would happen to protein made if DNA sequence was changed? –Wrong protein made –Wrong shape of protein This would make protein unusable!This would make protein unusable!

10. Gene Mutations: Point Mutations 1.POINT MUTATION: Base could be switched from one to anotherBase could be switched from one to another –EX: TCA on DNA makes mRNA AGU codes for Serine »If T changed to G, would be CGU which codes for ArginineArginine »Wrong AMINO ACID is coded for which means, wrong SHAPE or PROTEIN is made

11. Gene Mutations: Frame-Shift 2. FRAME-SHIFT: –A base could be deleted or added –EX: TCATTT on DNA; mRNA = AGUAAA codes for Serine +LysinemRNA = AGUAAA codes for Serine +Lysine If the T is deleted in the DNA, now is GUAAAIf the T is deleted in the DNA, now is GUAAA Ribosome will read GUA first which is for ValineRibosome will read GUA first which is for Valine –Similar if a base is added –Wrong AMINO ACID is coded for = wrong PROTEIN made OR Translation will abruptly STOP

12. Summary of Mutations Must occur in sex cells to be passed onMust occur in sex cells to be passed on Not all mutations are bad (depends on environment)Not all mutations are bad (depends on environment) Ultimate source of variation within a species!!!!!!Ultimate source of variation within a species!!!!!! –Take humans for instance….do we all look the same????????? Caused by:Caused by: –Exposure to radiation (ex. UV Rays) –Exposure to certain chemicals (in cigarettes, emitted from factories)

13. The Human Genome Human Chromosomes (46 in a normal human cell!) Two types:Two types: –Normal chromosomes: 44 in each BODY CELL; 22 in each GAMETE (sex cell) –Sex chromosomes: 2 in each BODY CELL; 1 in each GAMETE (sex cell) MALE: X and YMALE: X and Y FEMALE: X and XFEMALE: X and X Chances for having a boy or a girl?Chances for having a boy or a girl?

14. Chances for having a boy or girl? 50% OF COURSE…LET’S SEE! X Y X XXX XXXX X XX XX XYXYXYXY XYXYXYXY

15. Environmental Expression Some genes are “turned on” under certain environmental conditions EX. Himalayan Rabbit: Fur changes color due to TEMPERATURE changeEX. Himalayan Rabbit: Fur changes color due to TEMPERATURE change –WARM = White fur (no pigment produced) –COLD = Black fur Why does this make sense? Because black absorbs the heat, helping little bunny rabbit to stay warmBecause black absorbs the heat, helping little bunny rabbit to stay warm