Genotype vs Phenotype Genotype: An organism’s genetic makeup which consists of the alleles that an organism inherits from it’s parents (ex: Ee, EE, or ee) Phenotype: The physical appearance of an organism’s genotype.

Homozygous vs Heterozygous Homozygous: When both alleles of a pair are alike for a specific characteristic. An organism can be homozygous dominate (EE) or homozygous recessive (ee) Heterozygous: When both alleles in the pair are different. (Ee)

Probability Probability = # of times expected to happen # of times could happen Example: In Mendel’s experiment the tominate trait of yellow seed color appeared in F2 generation 6,022 times. The recessive trait of green seed color appeared 2,001 times. The total number of individuals was 6, = 8,023. What is the probability of the dominate trait?

Probability Probability of dominate trait = 6,022 =.75 or 75% 8,023 This can be expressed in either a percentage, fraction, or a ratio Probability tells us that there are three chances in four that an offspring of two heterozygous individuals will have the dominate trait and one chance in four that the offspring will have the recessive trait.

Monohybrid Crosses Monohybrid Cross: a cross that only one characteristic is tracked is monohybrid. Punnett Square: a diagram used to aid biologists in predicting the probable distribution of inherited traits in offspring. Six Examples: 1. Homozygous X Homozygous 2. Homozygous X Heterozygous 3. Heterozygous X Heterozygous 4. Testcross 5. Incomplete Dominance 6. Codominance

Example One: Homozygous X Homozygous There is a 100% probability that the offspring will have one specific genotype, thus producing the same phenotype.

Example Two: Homozygous X Heterozygous Will produce an outcome 50% probability dominate or recessive.

Example Three: Heterozygous X Heterozygous ¼ BB, ½ Bb, ¼ bb Genotypic Ratio: 1BB: 2Bb: 1 bb Phenotypic Ratio: 3 Brown, 1 Blue

Example Four: Testcross How can you determine if a guinea pig is homozygous (BB) or heterozygous (Bb)? Perform a Testcross: taking an individual with an unknown genotype and crossing it with another individual who is homozygous

Example Five: Incomplete Dominance Incomplete dominance occurs when the phenotype of a heterozygote is intermediate between the phenotypes determined by the dominant and recessive traits. Pink flowers (Rr) come from a dominant homozygous red parent (RR) and a recessive homozygous white parent (rr).

Example Six: Codominance Codominance occurs when both alleles for a gene are expressed in heterozygous offspring. Neither allele is dominant or recessive, nor do the alleles blend in the phenotype (as in incomplete dominance).

Dihybrid Cross Dihybrid cross: is a cross which two characteristics (genes) are tracked. The offspring of the animal being crossed in a dihybrid cross is called a dihybrid. Two examples: 1. Homozygous X Homozygous 2. Heterozygous X Heterozygous

Example One: homozygous X homozygous Review to page 185 Two seeds with two different genes being expressed: (1) round, yellow seed (RRYY) (1) wrinkled, green (rryy)

Example Two: Heterozygous X Heterozygous Use the same procedure as in homozygous x homozygous.