1. Heredity: Monohybrid Cross 5.3

2. Heredity: Monohybrid Cross 5.3
1. Gregor Mendel made a major contribution to Biology.
He learned that each kind of cross-breeding experiment produced offspring with a certain ________ of the traits he was studying.
Ex: In his F1 generation, he found that all of the offspring expressed the ____________ phenotype;
The F2 generation expressed a ratio of ____ dominant phenotypes to ____ recessive phenotype.
He also found he could predict the outcome of a cross by using ____________.
ratio
dominant 3 1
probability

3. Probability
2. Probability is the ___________ that something will happen.
It can be expressed as a:
Fraction (1/2)
Decimal (0.5)
Percent (50%)
Probability = number of all possible outcomes
What is the probability that a die will land
the1? ______________
likelihood
1/6, 1:6

4. Important Terms
3. A ___________ cross is a cross-breeding experiment that can be used to determine how ____ trait (pair of genes) can be inherited. 4. A ____________ can be used to determine the expected outcome of a cross. It is named after its inventor, Reginald __________. 5. The _________ and __________ ratios can be found using a Punnett square.
monohybrid 1
Punnett square
Punnett
genotypic
phenotypic

5. Cross Experiment
6. The genotypic ratio is the ratio of genotypes among the offspring of a cross.
It states the __________ of individuals with each different genotype observed among the offspring.
7. The phenotypic ratio is the ratio of phenotypes among the offspring of a cross.
It states the __________ of individuals with each different phenotype observed among the offspring.
number
number

6. Seed Shape in Garden Peas
8. Use a monohybrid cross to study the inheritance of seed shape in garden peas. A round seed shape is the dominant trait (R) and a wrinkled seed shape is the recessive seed shape (r).
Generation P F1
Round Wrinkled X
RR rr
Genotypic ratio:
Genotypic Frequency:
Phenotypic Ratio:
Phenotypic Frequency:
4:4 Rr
Homozygous
Dominant
Homozygous
Recessive
r r
100% Rr Rr R
4:4 Round
100% Round

7. Seed Shape in Garden Peas
Generation F2
Genotypic ratio:
Genotypic Frequency:
Phenotypic Ratio:
Phenotypic Frequency:
1RR: 2Rr: 1rr
R r
25% RR, 50% Rr, 25% rr RR Rr rr R r
3 Round: 1 Wrinkled
75% Round
25% Wrinkled

8. Assessment
9. What do the letters at the top and left side of a Punnett square represent?
________________________________________
10. What do the boxes in a Punnett square represent?
The parent’s alleles in each gamete
Possible offspring genotypes