11 1 Gregor Mendel 11 2 Punnett Squares

11 -1 Gregor Mendel 11 -2 Punnett Squares S

Bell Work Why do children resemble their parents? They inherit their parents characteristics through alleles- forms of genes.

Bell Work S What are dominant and recessive alleles? Alleles are forms of a gene. The dominant form of an allele is the form whose trait shows up if it is present. The recessive allele is the form whose trait only shows up when the dominant allele is not present.

11 -1 Inheritance 1. Every living thing has a set of ______ inherited from its parent or parents. Characteristics Heredity holds the key to understanding what makes each species unique.

11 -1 2. The scientific study of heredity is called _____. Genetics

11 -1 Gregor Mendel Who was Gregor Mendel? An Austrian monk, born in 1822. His experiments with pea plants laid the foundations of the science of genetics.

11 -1 Gregor Mendel’s Peas 3. What do we know as true about Gregor Mendel’s garden peas? S The male portion of the plant produces sperm (in pollen). The female portion of the plant produces egg cells. S Fertilization produces a new cell, which develops into a tiny embryo encased within a seed. S Pea Plants are normally self-pollinating.

11 -1 4. What does it mean when pea plants are described as being true breeding? It means that if they are allowed to self-pollinate, they would produce identical offspring.

11 -1 5. To perform his experiments, how did Mendel prevent pea flowers from self-pollinating and control their crosspollination? To prevent self-pollination, Mendel cut the pollen bearing male part and dusted this pollen onto another flower. This process is known as cross-pollination.

11 -1 6. Genes – C chemical factors that determine traits 7. Hybrids B the offspring of crosses between parents with different traits

11 -1 8. Traits A specific characteristics that vary from one individual to another 9. Alleles D different forms of a gene

11 -1 10. The principle of dominance states… that some alleles are dominant and some alleles are recessive. 11. True or False: An organism with a recessive allele for a particular form of a trait will always exhibit that form. False- The organism with a recessive allele will only exhibit that form when the dominant allele for the trait is not present.

11 -1 12. Which traits were controlled by dominant alleles in Mendel’s pea plants? Tall & Yellow Which traits were controlled by recessive alleles? Short & Green

11 -1 Mendel called each original pair of plants the P Generation (parental) and the offspring of these the F 1 generation (first filial) Mendel produced hybrids when he crossed parents with different traits; and to his surprise the offspring only resembled one of the parents.

11 -1 Segregation Mendel wanted to know the answer to another question: Had the recessive alleles disappeared, or were they still present in the F 1 plants? P generation F 1 Generation F 2 Generation

11 -1 13. How did Mendel find out whether the recessive alleles were still present in the F 1 plants? He allowed all seven kinds of F 1 hybrid plants to produce an F 2 generation.

11 -1 14. About one fourth of the F 2 plants from Mendel’s F 1 crosses showed the trait controlled by the ______ allele. Recessive

11 -1 Results of the F 1 Cross ** Mendel assumed that a dominant allele had masked the corresponding recessive allele in the F 1 generation. • However, the trait controlled by the recessive allele showed up in some of the F 2 plants. • ** This reappearance indicated that at some point, the allele for shortness was segregated, or separated, from the allele for tallness. • Mendel suggested that the alleles for tallness and shortness in the F 1 plants segregated from one another during the formation of the gametes. What are gametes? • Gametes are the Sex Cells

11 -1 F 1 Generation T 17. t T t Gametes F 2 Generation T t T T T t t t

11 -1 19. What is segregation? What happens to alleles during segregation? Segregation is the separation of paired alleles; the alleles are separated during the formation of gametes, with the result that each gamete carries only a single allele from the original pair.

Monohybrid Cross Complete the Punnett Square:

Punnett Square Solution

11 -2 Probability and Punnett Squares 1. The likelihood that a particular event will occur is called ______. Probability 2. What is the probability that a single coin flip will come up heads? 50%

11 -2 3. True or False: The past outcomes of coin flips greatly affect the outcomes of future coin flips. False: past outcomes do not affect future ones 4. Why can the principles of probability be used to predict the outcomes of genetic crosses? The way in which alleles segregate is completely random, like a coin flip.

11 -2 5. How do geneticists use Punnett Squares? The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett Square. 6. How do we complete the Punnett Square for Tt x Tt T T T t

Tt x Tt Punnett Square

11 -2 Matching 7. Genotype. D. Genetic makeup of an organism (Tt) 8. Homozygous – A Organisms that have two identical alleles for a particular trait (TT or tt)

11 -2 Matching 9. Phenotype. C Physical characteristic of an organism 10. Heterozygous. B Organisms that have two different alleles for the same trait (Tt)

11 -2 11. True or False: Homozygous organisms are true-breeding for a particular trait. True: TT true-breeding Tt hybrid 12. True or False: Plants with the same phenotype always have the same genotype. False

Yellow vs Green Plants If Y is Dominant Yellow and y is recessive green Which of the following plants would be yellow? a. YY b. Yy, c. yy

11 -2 13. Which are true about probability and segregation? B, C, and D A. Is True If : In an F 1 cross between two hybrid tall pea plants (Tt), ¼ of the F 2 plants will have two alleles for tallness (TT)

11 -2 14. In Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F 2 generation? 3: 1 3 Tall plants for every 1 short plant

F 2 Generation

11 -2 15. True or False: Probabilities predict the precise outcome of an individual event. False: probabilities predict the average outcome 16. How can you be sure of getting the expected 50: 50 ratio of flipping a coin? Flip the coin many times

11 -2 17. The _____ the number of offspring from a genetic cross, the closer the resulting numbers will get to expected values. larger 18. True or False: The ratios of an F 2 generation are more likely to match Mendelian predicted ratios if the F 1 generation contains hundreds or thousands of individuals. True

Exit Ticket Question What is the difference between genotype and phenotype?