Chapter 11-2: Fundamentals of Genetics

1. Chapter 11-2: Fundamentals of Genetics

2. Homozygous vs. heterozygous • Homozygous = alleles for a certain trait are the same. • aa, AA • Heterozygous = alleles for a certain trait are different. • Aa 11-2

3. Genotype vs. Phenotype • Genotype = genetic makeup of an organism. • aa, AA, Aa • Phenotype = Physical expression of genotype. • Tall, short “How do you Pheel Physically?” 11-2

5. Probability in genetics • Mendel grew thousands of plants and arrived at his laws after counting many offspring. • Laws of chance explain his findings. 11-2

6. The larger the number of trials (flips), the closer the ratio comes to the expected ratio. 11-2

7. This is an example of the basic law of probability. When several possible events can happen and There is no bias then There is an equal chance of them all happening. 11-2

8. What does this have to do with genetics? 11-2

9. The law of probability allows us to predict what offspring will result from a genetic cross. = ? x

10. Probabilities Predict Averages Probabilities predict the average outcome of a large number of events (not necessarily the exact outcome). 11-2

11. The Punnett Square My name is Spongebob Punnett Pants Punnett 11-2

12. Punnett Square • Helpful way to predict the results of a cross. • The PS shows all possible outcomes of a genetic cross. 11-2

13. Setting up a Punnett Square is like determining possible outcomes from flipping 2 coins.

14. 2 Coins: h H H H H h H H h h h h

15. Punnett Squares • A capital letter represents the dominant allele for tall. • A lowercase letter represents the recessive allele for short. • In this example, • T = tall • t = short

16. Parent 2 gametes Punnett Square TT T T t Parent 1 t tt 11-2

17. 11-2

18. Monohybrid (single gene)

19. 11-2 • Probability can be used to predict • average outcome of many events. • precise outcome of any event. • how many offspring a cross will produce. • which organisms will mate with each other.

20. Compared to 4 flips of a coin, 400 flips of the coin is • more likely to produce about 50% heads and 50% tails. • less likely to produce about 50% heads and 50% tails. • guaranteed to produce exactly 50% heads and 50% tails. • equally likely to produce about 50% heads and 50% tails.

21. Organisms that have two different alleles for a particular trait are said to be • hybrid. • heterozygous. • homozygous. • recessive.

22. Two F1 plants that are homozygous for shortness are crossed. What percentage of the offspring will be tall? • 100% • 50% • 0% • 25%

23. The Punnett square allows you to predict • only the phenotypes of the offspring from a cross. • only the genotypes of the offspring from a cross. • both the genotypes and the phenotypes from a cross. • neither the genotypes nor the phenotypes from a cross.