1. Probability

2. Genotype
Ratio %
Phenotype Yy
4:4
100
Yellow

3. Draw the Punnett SquareY y

4. Draw the Punnett SquareY y Yy

6. Draw the Punnett SquareY y

7. Y y YY Yy yy Y y

8. Genotype
Ratio %
Phenotype YY
1:4 25
Yellow
3:4 75 Yy
2:4 50 yy
Green

9. Probability
Punnett squares show all possible combinations of gametes and the likelihood that it will occur
Results will not ALWAYS fit the exact ratios
Genetics has a ‘chance’ factor
Probability (or chance) that an event will occur is determined by dividing the number of desired outcomes by the total number of possible outcomes

10. Calculating Probability (P)
Toss a coin, it can land on heads or tails
The P of getting heads (the desired outcome) out of 2 (the total number of possible outcomes, as a coin can only have heads or tails)
P (heads)= 1:2 or ½

11. Data Analysis Results of a heterozygous round seed cross:
Calculate the actual ratio of round-seeded plants to wrinkled-seeded plants by dividing the number of round-seeded plants by the number of wrinkled-seeded plants
MeKind of Plant
NuNumbNumber of Plants
Round seeded
5474
Wrinkled seeded
1850
Whatis the ratio , write the number (ie. 5:1)
How does this ratio observed compare with the expected 3:1 ratio?

12. R r

13. R r RR Rr rr
P of

14. P(round seeds) is 3:4
Sample size does not exactly fit predicted ratio
Important to note that results predicted by probability are more likely to be seen when there is a large number of offspring
Larger the sample size, the better