2. Genetics Rules Rule #1? Rule #2: Incomplete dominance  some alleles aren’t completely dominant so they BLEND Rule #3: Codominance  some alleles dominate together so BOTH ARE SEEN Rule #4: sex-linked genes  ALL alleles on a male’s X chromosome (X-linked) are expressed.

3. Complete Dominance Rule #1—some alleles completely dominate over others: B=brown eyes b=blue eyes Bb= brown eyes, so B is completely dominant.

4. Incomplete Dominance Rule #2—some alleles DON’T COMPLETELY DOMINATE, so they blend: RR= red flowers rr = white flowers Rr = pink flowers PINK FLOWERS!!! BLENDING!!!

5. Codominance Rule #3—some alleles dominate TOGETHER so they BOTH are shown H = brown hair on horses H’ = white hair on horses HH’ = both brown and white hairs, so the horse is roan color. Blood types are like this, too.

6. Roan Horse

7.  Antigens-markers on cells  Blood type determined by your carbohydrate markers on your red blood cells  4 blood group phenotypes:  Type A has A antigens  Type B has B antigens  Type AB has A and B antigens  Type O has no antigens Blood Types

8. Multiple Alleles  Multiple alleles- 3 different forms of the gene code for blood types I A, I B, and i Allele I A makes an “A” antigen I B makes a “B” antigen i makes none 6 blood group genotypes Complete dominance- I A and I B dominate over i Codominance- I A I B genotype shows BOTH A and B carbs

9. Blood Types Reactivity to blood transfusions and organs: Antibodies-proteins produced by your immune system to fight off things that look “foreign.” Type A (makes anti-B antibodies) Type B (makes anti-A antibodies) Type AB (makes NO antibodies—universal receiver) Type O (makes anti-A and anti-B antibodies— universal donor)

10. Free Write Journal Entry Why? Take time to absorb the material and think about and process the information. What should you do? Take a couple of minutes to write down any thoughts, questions, or ideas at the bottom of your notes. There are no right or wrong entries, as long as you try.

11. Sex-Linked Genes Rule #4: sex-linked genes  ALL alleles on a male’s X chromosome (X-linked) are expressed. Male sex chromosomes?_________ Female sex chromosomes?_________ We also call sex-linked genes by another name, X-linked, because the X chromosome has the majority of the genes.

12. Sex-Linked Genes In males, EVERY gene on their X chromosome is expressed. The Y doesn’t have the same genes. In females this is not the case because they have another copy on their other X chromosome to overcome it.

13. Sex-Linked Genes Examples of sex-linked disorders: Colorblindness Hemophilia Fragile X Syndrome Duchene Muscular Dystrophy Cleft Palate Vitamin D Resistant Ricketts 3 types of deafness Male Pattern Baldness

14. Sex-Linked Genes The genes that occur on the sex chromosomes must be written with X’s and Y’s to show this special situation. For example: red-green colorblindness is a recessive trait. It is found on the X chromosome, not the Y. We write the alleles (forms of the gene) this way: X C = colorblindness X C = normal

15. Sex-Linked Genes Try to complete this table: PhenotypesGenotypes Normal Male Colorblind Male Normal Female Normal “carrier” Female Colorblind female