Laboratory Investigation #11
Inheritance
Description of the Lab
The lab will help clarify terms such as homozygous, heterozygous, genotype,
phenotype, dominance and incomplete dominance. It will show the relationship of the
genotype and phenotypes between parents and children. Students will be introduced to a
Suggestion: have students work in groups of 4
Outline of Investigation
1. Dominance & Recessive Alleles Influence Phenotype
A. Purple starchy corn ears, yellow starchy corn ears
2. More Monohybrid Crosses
3. Human Inheritance
A. Students check themselves
B. Same as above
Laboratory Materials and Equipment for Student Use
Materials and Equipment
Per
Student
Per Pair of
Students
Per Lab
Group
Per
Room
Corn mounts of a monohybrid cross
7
Plant tray (8x12x2 ¾)
Bag of Potting soil
1
Automatic timer
1
Fresh Live Material
Green:albino genetic corn seed pack
7
Green:yellow green:yellow (1:2:1) F2
soy bean seed pack
1
7
Preparation of laboratory Materials and Reagents
Three to four weeks prior to this lab
1. Prepare 2 plant trays for each group of 4 students. One plant tray will have 50
One week prior to the lab
1. Continue to water the seedlings.
Questions for Lab #11 Inheritance
Use the knowledge you acquired in this lab exercise, along with information from your
textbook, to answer the following questions.
1.In Investigation 1 you counted a large number of kernels to obtain the 3 to 1 phenotype
ratio. If you counted only a small number of kernels, the ratio may deviate from the 3 to
1 ratio. Why?
2. A pea plant producing smooth peas (a dominant trait) is crossed with a pea plant that
produces wrinkled peas (recessive trait). Fifty percent of the offspring from this cross
produce smooth peas and the other fifty percent produce wrinkled peas. What is the
genotype of the smooth-seeded parent? Show your reasoning using a Punnett square.
S s
3. The mutation that resulted in an allele that interfered with chlorophyll synthesis gave
rise to a white (chlorophyll-less) phenotype when homozygous. This allele is an example
of a recessive lethal allele. What does this mean?
How is this lethal allele maintained in a population?
4. A variety of radish that produces globe-shaped tap roots is crossed with a variety that
produces elongated tap roots. The F1 offspring of this cross produced oval tap roots.
When the F1 offspring were self fertilized, 25% of the F2 offspring produced globe–
shaped, 50% produced oval-shaped, and 25% produced elongated tap roots. What is
being illustrated in these crosses?
Incomplete dominance
What are the genotypes for the parents, F1 offspring and the F2 offspring?
5. Both parents of a blue-eyed student have brown eyes. What does this information tell
you about the genotypes of the student’s parents?