1. Shut up, Darwin So much for genius!

2. All of the inheritance patterns we have learned about so far, such as the one’s from Mendel’s experiments, are often referred to as simple Mendelian inheritance. This would include any inheritance which is controlled by a single pair of alleles, one dominant, and one recessive. Many inheritance patterns are far more complex than those studied by Mendel. Some of these types of inheritance don’t even involve chromosomes! Polygenic Inheritance

3. When inheritance follows the rule of dominance, then the homozygous dominant, and the heterozygous individuals all have the same phenotype. TT= Tt = tt = The allele for tall = T; the allele for short = t tall short When traits are inherited in a pattern where the heterozygous individual is intermediate between those of the two homozygotes, then the pattern is called Incomplete Dominance. TT =tall tt =short Tt =Average height

4. Red Snapdragons X White Snapdragons = Pink Snapdragons When showing incomplete dominance, the alleles look like this: R=redR 1 =white Neither is dominant to the other, so no lower case letter appears. Can you predict what happens when you cross two pink snapdragons? Do a punnett square crossing RR 1 x RR 1

5. RR1 RR1 R R 1 RRRR 1 R1R1R1R1 The snapdragons appear in the F2 generation in a 1:2:1 phenotypic ratio The genotypic ratio is also 1:2:1 This result supports Mendel’s law of segregation, meaning that the alleles combine during fertilization completely randomly in four possible ways.

6. Codominance is apparent in a breed of chicken, where black feathers are B, and white feathers are W. Both are dominant, so both are expressed with a capital letter. X= When codominant alleles are expressed, both phenotypes are present equally. BBWW BWBW

7. The proteins in our blood cell’s structure is controlled by three alleles; i, I A and I B. Humans can have one of four possible blood types: A; B; O; and AB Human blood is separated into different classifications because of the varying proteins contained in each blood type's red blood cells. These proteins are there to identify whether or not the blood in the individual's body is it's own and not something the immune system should destroy. If the recessive allele i is paired with I B or I A, it's phenotypic expression is hidden. When the I B and I A are together in a pair, both proteins A and B are present and expressed. The i allele is the only recessive allele I A and I B are both codominant I A I A =Type A I B I B =Type B ii=Type O I A I B =Type AB

8. Question: What are the genotypes of a man and woman, each with type A, and B blood respectively, who produce offspring with types A, B, O and AB? ABB AO Let’s not forget to show the offspring’s actual genotypes! Now it becomes obvious what their genotypes were. IAIBIAIB IBiIBi IAiIAiii IBiIBi I A i RH, or Rhesus factor is inherited separately from the blood type, and follows the rules of polygenic inheritance. About 85% of humans globally contain the Rhesus positive phenotype, which means they contain the Rh+ antigen on the surface of their red blood cells.

9. A woman with Type O blood and a man who is Type AB are expecting a child. What are the possible blood types of the offspring? i i IAIBIAIB IAiIAi IBiIBi IAiIAi IBiIBi This couple can only have offspring that are types A, and B. Can a person with type AB blood ever produce a child with type O blood? NO!!! Blood groupings of humans not only follow the rules of codominance, but also are determined through multiple alleles. I A ; I B ; i

10. While many traits are controlled by a single pair of alleles, some traits can be controlled by more than two alleles. These traits are said to be carried and expressed by multiple alleles. In the case of rabbit fur color, there are four different alleles which determine different phenotypes. Chinchilla rabbit Dark-gray colored C=dominant to all other alleles c ch = dominant to Himalayan and to white Himalayan rabbit c h = dominant to white White rabbit c = completely recessive Try predicting how many possible genotypes would code for chinchilla rabbits. Remember, while there may be multiple alleles in a population that determine a trait, each individual only inherits a pair of these alleles…one from mother, and one from father! Human blood types are not only codominant, but multiple allele!

11. Traits controlled by genes located on the sex chromosomes are called sex-linked traits. In humans, there are 23 pairs of chromosomes in all autosomal cells within the body. The 23 rd pair are sex chromosomes. The presence of the Y chromosome in one of these karyotypes, makes one of these individuals a male. When there are two X’s, then it is a female The male genotype is XY, the female genotype is XX

12. The alleles for sex-linked traits are written as superscripts of the X or Y chromosome…depending upon which chromosome they are associated with. Because males only inherit one X chromosome, when a recessive trait is inherited on the X chromosome there is no corresponding trait to mask that trait on the Y chromosome…so the recessive trait is always expressed In fruit flies, the allele for eye color is on the X chromosome. X R =red eyes X r =white eyes What would the genotype of a white- eyed female look like? XrXrXrXr What would the genotype of a red- eyed heterozygous female look like? XRXrXRXr What would the genotype of a red-eyed homozygous dominant female look like? XRXRXRXR Predict what the genotype of a white-eyed male would look like. XrYXrY

13. Create a punnett square showing the mating results of a homozygous dominant female fruit fly for eye-color, and a male fruit fly with the recessive trait. Because there is no second X chromosome in the male, it cannot be homozygous. Instead, it is called hemizygous. X r Y XRXRXRXR XRXrXRXr XRYXRY XRXrXRXr XRYXRY What color eyes will the males have? What color eyes will the females have? Predict what genotypic combinations would create white-eyed male flies. Thomas Hunt Morgan discovered that traits were linked to sex chromosomes, through his study of fruit flies.

14. Hemophilia is characterized by inability to form blood clots because of deficiency in a clotting factor in the blood. The frequency of hemophiliacs is about 1 in 10,000 males. Affected individuals suffer from severe bleeding following a relatively small injury like a cut or a bruise. Duchenne Muscular Dystrophy affects young boys. It is characterized by muscular degeneration and weakness beginning at the age of 3 to 5 years and progressing rapidly so that affected individuals are wheel-chair bound by the time they are in their teens and die in their early twenties because of severe involvement of their respiratory muscles. Red-green color blindness is the inability to distinguish red from green.

15. An individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

16. How can you tell quickly, that this must be a sex-linked trait? Only the males have it!

17. Some traits, such as skin, eye color and height in humans vary over a wide range. These traits are governed by many genes, or polygenic inheritance.

18. Skin Color: A Polygenic Trait Scientists have found that when light-skinned people mate with dark-skinned people, their offspring have intermediate skin colors, similar to what you might expect with incomplete dominance. When intermediate skin-colored children mate with each other, the resulting skin color range from the light-skin color to the dark-skin color of the original parents. =X

19. Gametes contributed by parents ABC ABcAbCAbcaBCaBcabC abc ABC65545443 ABc54434332 AbC54434332 Abc43323221 aBC54434332 aBc43323221 abC43323221 abc3221c2110 ABC = dark pigmentation abc = light pigmentation As you can see, this individual offspring would inherit the darkest pigmentation, whereas this offspring would inherit the lightest pigmentation. This makes it easier to understand how two offspring of biracial ancestry can actually pass on the darkest, or the lightest pigmentation to their offspring (even though the odds are against it! ) AaBbCc x AaBbCc What are the odds of this couple producing an aabbcc individual? AABBCC? 1/64

20. Sometimes the genetic makeup of an organism determines only that organism’s potential to develop and function in a particular way. As the organism develops, many factors can influence how the gene is expressed, or even whether the gene is expressed at all. Influence of external environment: Temperature, nutrition, light, chemicals, and infectious diseases can influence gene expression. Arctic Fox Influence of internal environment: Hormones can influence horn size in mountain sheep.