APW

1. APW • If you flip a coin, what are the chances that it will land on heads? Tails? • Suppose you flip the coin once, get heads, and then flip it again. What are the chances that you will get heads again? Explain.

2. APW 3-20-08 Fill in the following Punnett Square. Define: Purebred - Define: Hybrid- Define: Testcross-

3. APW 3-20-08 Fill in the following Punnett Square. Define: Purebred-having the same alleles Define: Hybrid-having two different alleles Define: Testcross-when you cross an organism with a homozygous recessive genotype with a dominant phenotype to figure out the dominant trait organisms genotype.

4. APW 3-24-08 Fill in the following Punnett Squares.

5. Chapter 3 Section 2 Traits and Inheritance

6. Objectives • Explain how genes and alleles are related to genotype and phenotype • Use the information in a Punnett square • Explain how probability can be used to predict possible genotypes in offspring. • Describe three exceptions to Mendel’s observations

7. Genes Bigger • Genes are one set of instructions for an inherited trait. • Each parent gives one set of genes to offspring. • Therefore, offspring has two sets of a gene for every characteristic. • Genes are located on chromosomes. Smaller

8. Alleles • Alleles are the different forms of a gene. • Characteristics are to traits as genes are to alleles.

9. Phenotype vs. Genotype • A phenotype is any observed quality of an organism, such as its morphology, development, or behavior. • A genotype is the inherited instructions an organism carries, which may or may not be expressed. Genotype Phenotype

10. Phenotypes of Pea Plants • Name 2 possible phenotypes for flower color. ______________ _______________ • Name 2 possible phenotypes for seed shape. ______________ _______________ • Name 2 possible phenotypes for seed color. ______________ _______________

11. Genotypes of Pea Plants • Name 3 possible genotypes for flower color if the alleles are F and f. ___________ ___________ ___________ • Name 3 possible genotypes for seed shape if the alleles are S and s. ___________ ___________ ___________ • Name 3 possible genotypes for seed color if the alleles are C and c. ___________ ___________ ___________

12. Genotype: Homozygous vs. Heterozygous • A Homozygous plant is one with two dominant or two recessive alleles. • A Heterozygous plant is a plant with two different alleles HH or hh Hh

13. Punnett Squares • Punnett Squares are used to organize all of the possible combinations of offspring from particular parents. • What is the ratio of dominant phenotypes to recessive phenotypes? _______________ Using a punnett square to model Mendel’s first experiments

14. Punnett Squares • Punnett Squares are used to organize all of the possible combinations of offspring from particular parents. • What is the ratio of dominant phenotypes to recessive phenotypes? • _______________ Using a Punnett square to model Mendel’s second experiments

15. What are the chances? • When the alleles a parent has are different, the chances of receiving them are fifty-fifty, like a coin toss. • Probability is the mathematical chance that something will happen. In this case, it is the chance that a trait will be inherited. • Probability is usually written as a fraction or a percentage.

16. Probability Practice • If you roll a pair of dice, what is the probability that you will roll 2 threes? ______ x ______ = ______ • If you flip a coin twice, what is the probability that you will get 2 heads? ______ x ______ = ______ • If you roll a single die, what is the probability you will roll an even number? ______ + ______ + ______ = ______

17. Probability Practice • If both parents have Pp genes, what is the probability that the offspring will have PP genes? ______ x ______ = ______ • If both parents have Pp genes, what is the probability that the offspring will have Pp genes? ______ x ______ + ______ x ______ = ______ • If both parents have Pp genes, what is the probability that the offspring will have pp genes? ______ x ______ = ______

18. Exceptions to Mendel’s Principles • Incomplete Dominance • Codominance • One gene, many traits • Many genes, one trait • Environmental Effects

19. Incomplete Dominance • When an individual is heterozygous for a trait, instead of one trait being completely dominant over another, the traits mix. • Thus, you can tell the genotype by looking at the phenotype for incomplete dominance.

20. Codominance • In codominance, neither phenotype is recessive. Both traits are fully expressed. • However, both codominant traits are dominant over the recessive trait. • Blood type is an example

21. One Gene, Many Traits • What do you notice about the tiger? • Sometimes one gene influences more than one trait. • In tigers, the gene that influences eye color also influences hair color.

22. Many genes, One trait • Skin color and eye color are influenced by many genes. • That is why there are intermediary colors. Environment • Environments can also affect phenotype (hair cutting)

23. Objectives • Explain how genes and alleles are related to genotype and phenotype • Use the information in a Punnett square • Explain how probability can be used to predict possible genotypes in offspring. • Describe three exceptions to Mendel’s observations