Gregor Mendel -Breeded purple and white flowered pea plants and observed the flower color. -Noticed the 3:1 ratio of purple flowers to white flowers m/2010/06/gregor-mendel-and-pea- breeding.html “Hmmm… why is this happening?!” 

Terms to Know! (These will be Helpful!) A. Alleles: The alternative versions of a gene. A potential characteristic for an organism. 1. Example: In pea plants, the plant’s flower can either be white or purple. White and purple are the alleles. B. Dominant Allele: The allele that determines the organism’s appearance. (Always written in capitalized italic letters. Ex: AA ) C. Recessive Allele: The allele that does not have noticeable effect on an organism’s appearance. (Always written in lowercase italic letters. Ex: aa )

More Terms that will help you A LOT… D. Law of Segregation: An egg and sperm only carry one allele each for inherited character because the two members of an allele pair separate from each other during the production of gametes. E. Homozygous: An organism that has two identical alleles for a gene. (Hint: Homo=Same) F. Heterozygous: An organism that has two different alleles for a gene. (Hint: Hetero=Different) G. Phenotype: An organism’s physical traits. Ex: purple flowers vs. white flowers H. Genotype: An organism’s genetic makeup Ex: Pp, pp, or PP (This will make more sense after the next slide!!)

Punnett Square: A diagram used in the study of inheritance to show the results of random fertilization For example: In pea plants, purple flowers are the dominant allele (G), and white flowers are the recessive allele (g). This is the cross of one heterozygous and one heterozygous parent. In this case, each parent’s genotype is Gg. It’s offspring’s genotype will either be GG, Gg, or gg. The offspring has a 3:1 chance of being purple, because purple is the donimant allele. What color is each parent plant? PURPLE! Purple is each parent’s phenotype

Two Kinds of Crosses: 1.Monohybrid Cross: The crossing of organisms which only differ by one characteristic. Ex: Breeding pea plants with white and purple flower color. The only different characteristic between the two is their color. 2.Dihybrid Cross: The crossing of organisms that only differ by two characteristics. Example: pea seeds differ in both color and shape. They can be either yellow or green, and round or wrinkled.

Punnett Squares: Monohybrid Cross: y/Biology/Genetics/monocross.html Dihybrid Cross: Refer to picture in book on page 150.

Probability -All genetic crosses obey the rules of probability. These are the same rules that would apply to a coin toss, rolling dice, or drawing a card. -All genetic crosses abide by the rule of multiplication.

Rule of multiplication: The probability that a dual even is the product of the separate probabilities of the independent events. For example: The probability of flipping two coins and both landing on heads. -Probability of Coin 1 being heads: ½ -Probability of Coin 2 being heads: ½ -Probability of both coins being heads: ¼ -We get this because… ½ x ½ = ¼ (See page 152 for reference)

Any Questions? Now we get to fill in some punnett squares!!