Monohvbrid Cross Experiments
Objectives:
After completing this section, you should:
1. Define genotype and phenotype and describe their relationship.
2. Apply Mendel's Principle of Segregation.
3. Use the relationships among genes (alleles) to explain the inheritance
of specific traits.
4. Predict patterns of inheritance using a Punnett square
5. Design experiments to infer genotypes of individuals.
Key Terms:
genotype
phenotype
Principle of Segregation
gene
allele
locus
genome
true-breeding or pure-breeding
homozygous (homozygote)
heterozygous (heterozygote)
monohybrid
dominant
recessive
co-dominant
filial generation
testcross
reciprocal crosses
Punnett Square
gametes
somatic cells
progeny row
gene pair
mutagen
Online Lesson(s):
i) Just the Facts
ii) The Inheritance of Variation
(http://plantandsoil.unl.edu)
Inheritance of Variation
How does a geneticist (Dr. Jim Specht) explain the
inheritance of variation caused by
a chemical mutagen?
M1:
M2:
M3:
Three types of M3 rows
M2 selfed
M3 rows
All
progeny normal
Mutant and
normal progeny
All mutant
progeny
Mutagen: Includes mutations, genetic change
Gene:
Allele:
Gene Pair:
True breeding:
Monohybrid cross:
Phenotype:
Genotype:
Homozygous:
Heterozygous:
Dominant:
Recessive:
The Principal of Segregation
Genes in pairs in_________________ cells
Paired genes separate during_______________
_________ unite at___________ to form the next_____________
Think About It:
How do you prove that there are both
DD (homozygous) and Dd (heterozygous)
F2 tall plants when they both look the same?
Who was the first geneticist to use this
experimental approach to understand the
principles governing trait inheritance?
____ Dr. Jim Specht
____ Dr. George Beadle
____ Father George Mendel
____ Professor R.C. Punnett
Soybean Disease Lesion Mutant Data
Normal X Mutant
F1 plants
F2 plants
F3 rows from normal F2s
F3 plants from mixed rows
Mutant X Normal
F1 plants
F2 plants
F3 rows from normal F2s
F3 plants from mixed rows
Individual Plants
Normal
Mutant
5
18
---172
0
6
---46
Individual Plants
Normal
Mutant
6
81
---178
0
27
---49
Row Type
all
normal
row
mixed
row
8
10
Row Type
all
normal
mixed
row
row
29
52
Types of Generations and Crosses:
True-breeding parents –
F1 --
F2 --
F3 --
Testcross --
Reciprocal cross --
Punnett square --
Backcross -