Review of Terminology

1. Review of Terminology

2. Genotype • HereditaryInformation • internally coded, inheritable information • Genotype can be determined by direct observation of DNA

3. Phenotype • A phenotype describes any observed quality of an organism, such as its shape, development, or behavior • outward, physical appearance • Traits are small parts of the phenotype of an organism, such as the red color seen in the flower petals genotype +environment → phenotype

4. Heterozygous • Having two different alleles for a single trait. • Rr

5. Homozygous • Having identical alleles for a single trait. • RR or rr

6. Constructing a Punnett Square

7. What is a PUNNETT SQUARE? • A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine • A way to show phenotype & genotype • A chart that shows all the possible combinations of alleles that can result when genes are crossed

8. What is a PUNNETT SQUARE? • Letters stand for dominant and recessive alleles • An UPPERCASE letter stands for a DOMINANT allele • lowercase letters stand for recessivealleles

9. Using a PUNNETT SQUARE To set up a Punnett square, draw a large square, and then divide it into 4 equal sections (also squares). It should look something like this:

10. Using a PUNNETT SQUARE Now you need two parents to mate, ones with a known genotype For example, a red flower (genotype Rr) and a white flower (genotype rr). Rr x rr

11. Using a PUNNETT SQUARE Place one of the parents on top, and one on the left. You should get a something similar to this:

12. Using a PUNNETT SQUARE Finally, take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this:

13. Using a PUNNETT SQUARE • The two-letter combinations are the possible genotypes of offspring • They are: Rr, Rr, rr, and rr genotypes

14. Probability • Total possible combinations (number of squares in the table) becomes the denominator

15. Probability • Count the number squares for each combination • Rr = 2 (numerator) • rr = 2 (numerator)

16. Probability • Put the pieces together • Probability (chance) that a flower will have: • red phenotype, Rr = 2/4 or 50% • white phenotype, rr = 2/4 or 50%

17. Probability • Flip a coin ONCE • Number of total possible outcomes (this becomes the denominator) • Count the number of times you get a head or tail (numerator) • Probability = numerator/denominator

18. Probability • Flip a coin ONCE • Number of total possible outcomes (this becomes the denominator) = 2 (head or tail) • Count the number of times you get a head or tail (numerator) • Head = 1 • Tail = 0 • Probability of getting Head = numerator/denominator = ½ = 0.5

19. Probability • Flip a coin TWICE • Number of total possible outcomes (this becomes the denominator) = 4 (HH, HT, TH, TT) • Count the number of times you get each combination (numerator) : • HH = 1 • TT = 1 • HT or TH = 2 • Probability of both HEADS = numerator/denominator = 1/4 = 0.25 • Probability of both TAILS = numerator/denominator = 1/4 = 0.25 • Probability of HEAD AND TAIL = numerator/denominator = 2/4 = 0.5 H T H HH HT TT T TH