1. Unit: Mendelian Genetics

2. For example: ◦ Some alleles are neither dominant nor recessive. ◦ In most organisms, the majority of genes have more than two alleles. ◦ Many important traits are controlled by more than one gene.

3. Incomplete dominance - a condition in which offspring display an intermediate trait between two parents. Example: The F 1 generation produced by a cross between many red-flowered (RR) and white-flowered (WW) plants consists of pink-colored flowers (RW)

4. Codominance- a phenomenon in which two dominant alleles are expressed at the same time. Example #1 Speckled Chickens: In certain varieties of chicken, the allele for black feathers (B) is codominant with the allele for white feathers (W). ◦ Heterozygous chickens have a color described as “erminette,” (BW) speckled with black and white feathers.

6. If two erminette chickens were crossed, what is the probability that: a. They would have a black chick? b. They would have a white chick?

7. In horses and cattle, red coloration (R) and white coloration (W) are codominant. Individuals with each allele are roan (RW)

8. Take two minutes to summarize what you have learned by stating the similarities & differences that exist between traits that exhibit codominance and traits that exhibit incomplete dominance.

9. Multiple alleles- a term used to describe a gene with more than two alleles. Example: ABO blood groups in humans.

10. Alleles: I A I B and i A person only has two of these three alleles though! There are 4 possible blood types. Dominance I A and I B are both dominant over i, but neither is dominant over the other (A=B)

11. Type A blood Type B blood I A I A I B I B I A iI B i Type AB blood Type O blood I A I Bii

12. Answer: If the wrong blood type is used in a transfusion, antibodies in the recipients blood could attack the new blood received and make the person very ill.

13. Why are they called that? Since there are no antigens on the surface of Type O their blood cells, there is no risk of the antibodies in the recipients blood attacking the new blood received from a transfusion.

14. Why are they called that? Since people with AB blood have no antibodies for A or B, they can safely receive any type of blood in a transfusion.

15. Polygenic Traits: Traits that are controlled by two or more genes. Examples: human skin color, eye color, height ◦ The genes that code for the trait may be scattered along the same chromosome, or located on different chromosomes. ◦ Polygenic traits often show a wide range of phenotypes.

18. Take two minutes to summarize what you have learned regarding the similarities & differences that exist between traits that have multiple alleles and traits that are referred to as polygenic.

19. ◦ The characteristics of any organism are not determined solely by the genes that organism inherits. ◦ Genes provide a plan for development, but how that plan unfolds also depends on the environment. ◦ The phenotype of an organism is only partly determined by its genotype.

20. ◦ Western white butterflies that hatch in the summer have different color patterns on their wings than those hatching in the spring. ◦ Scientific studies show that butterflies hatching in springtime had greater levels of pigment in their wings than those hatching in the summer. ◦ In other words, the environment in which the butterflies develop influences the expression of their genes for wing coloration.

21. ◦ In order to fly effectively, the body temperature of the Western white butterfly needs to be 28– 40°C. ◦ Since it is cooler in the spring, more pigmentation allows a butterfly to reach the warm body temperature faster. ◦ Similarly, in the hot summer months, less pigmentation prevents the butterflies from overheating.

22. Take two minutes to summarize what you have learned regarding the role the environment has in gene expression.