1. Chapter 11.2 Pg. 302

2.  When red-flowered snapdragons (RR) are crossed with white-flowered snapdragons (rr) the heterozygous offspring have pink flowers (Rr)  Incomplete dominance, in which the heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes

3.  Both alleles are expressed in the heterozygous condition  Sickle-cell disease is an example of codominance ◦ Sickle-cells do not effectively transport oxygen  Individuals who are heterozygous for the trait have both normal and sickle-shaped red blood cells ◦ These individuals can lead relatively normal lives, as the normal blood cells compensate for the sickle-shaped cells.

4.  Scientists have discovered that those who are heterozygous for the sickle-cell trait also have a higher resistance to malaria  The death rate due to malaria is lower where the sickle-cell trait is higher  more people live to pass on sickle-cell, therefore the disease continues to increase in Africa

5.  Some forms are inheritance are determined by more than two alleles referred to as multiple alleles  Blood groups in humans ◦ ABO blood groups have three forms of alleles ◦ Blood also has Rh factors that determine whether the blood is positive or negative

6.  Coat color of rabbits  presence of multiple alleles increase the possible number of genotypes and phenotypes (Pg 304 in your book)  However, the four alleles for rabbit-coat color produce ten possible genotypes and for phenotypes ◦ Full color ◦ Albino ◦ Himalayan ◦ Chinchilla

7.  One allele hiding the effects of another allele is called epitasis ◦ Coat color in Labrador retrievers can vary from yellow to black ◦ Depending on the dominant allele either light or dark pigments will be displayed

8.  One pair or chromosomes, the sex chromosomes, determines an individual’s gender  XX  female  XY  male  The other 22 pairs of chromosomes are called autosomes

9.  The offspring's gender is determined by the combination of sex chromosomes in the egg and sperm cell Sperm X Sperm Y Egg X XX Female XY Male Egg X XX Female X Male

10.  Females have 22 pairs of autosomes and one pair of X chromosomes  Males have 22 pairs of autosomes and one X and one Y chromosome  X chromosomes are larger and carry a variety of genes  Y chromosomes mainly has genes that relate to the development of male charactistics

11.  Two X chromosomes would likely result in two does of the X chromosome ( and males would only get one)  To balance the difference in the dose of X- related genes, one X chromosome stops working this is called dosage compensation or X-inactivation  Dosage compensation occurs in all mammals

12.  Coat colors of the calico cat are caused by random inactivation of a particular X chromosome  The resulting colors depend on the X chromosome that is activated. The orange colors are formed by the inactivation of the X chromosome carrying the allele for black coat  Similarly the black colors are result of the activation of the X chromosome carrying the allele for orange coat color.

14.  Traits controlled by genes located on the X chromosome are called sex-linked traits  Males have only one X chromosome therefore they are affected by recessive X-linked traits more often than females  Examples of Sex-Linked traits ◦ Male-pattern baldness ◦ Red-green color blindness ◦ Hemophilia  delayed clotting of the blood

15.  Polygenic traits arise from the interaction of multiple pairs of genes  Example of Polygenic Traits: ◦ Skin color ◦ Height ◦ Eye color ◦ Fingerprint pattern

16.  Sunlight, water, and temperature are environmental influences that commonly affect an organism’s phenotype  Temperature influences the expression of genes. Notice the fur of the Siamese cat. The cat’s tail, feet, ears, and nose are dark, these areas of the cat’s body are cooler. ◦ Temperature affects the expression of color pigment in the fur