Lab 7 Mendelian Genetics BIO101L
Student Name:
Access Code (located on the lid of your lab kit):
Lab Report Format Expectations
Utilize college level grammar and professional formatting when completing this worksheet.
Pre-Lab Questions
1. In a species of mice, brown fur color is dominant to white fur color. When a brown
mouse is crossed with a white mouse all of their offspring have brown fur. Why did none
of the offspring have white fur?
Because the brown mouse must have been heterozygous (carrying one dominant brown
allele and one recessive white allele) while the white mouse is homozygous recessive.
Every offspring receives at least one dominant brown allele, so none show white fur.
2. Can a person’s genotype be determined by their phenotype? Why or why not? What is
the difference between genotype and phenotype?
No, because the phenotype (the observable traits) does not reveal the complete genetic
makeup. The genotype is the actual genetic code (the alleles present), whereas the
phenotype is the result of how those genes are expressed, often influenced by
dominance and environmental factors.
3. Are incomplete dominant and co-dominant patterns of inheritance found in human
traits? If yes, give examples of each.
Yes. In the ABO blood group system, the A and B alleles are co-dominant (producing AB
blood when both are present). An example of incomplete dominance in humans is less
common but may be observed in some cases of certain genetic disorders where
heterozygotes exhibit intermediate traits compared to homozygotes.
4. Consider the following genotype: Yy Ss Hh. We have now added the gene for height: Tall
(H) or Short (h).
a. How many different gamete combinations can be produced?
Each gene pair segregates independently. With three heterozygous gene
pairs, the number of gamete combinations is 2³ = 8.
b. Many traits (phenotypes), like eye color, are controlled by multiple genes. If
eye color were controlled by the number of genes indicated below, how many
possible genotype combinations would there be in the following scenarios?
5 Eye Color Genes: 243 combinations
, Lab 7 Mendelian Genetics BIO101L
10 Eye Color Genes: 59,049 combinations
20 Eye Color Genes: 3.49 billion combinations
Student Name:
Access Code (located on the lid of your lab kit):
Lab Report Format Expectations
Utilize college level grammar and professional formatting when completing this worksheet.
Pre-Lab Questions
1. In a species of mice, brown fur color is dominant to white fur color. When a brown
mouse is crossed with a white mouse all of their offspring have brown fur. Why did none
of the offspring have white fur?
Because the brown mouse must have been heterozygous (carrying one dominant brown
allele and one recessive white allele) while the white mouse is homozygous recessive.
Every offspring receives at least one dominant brown allele, so none show white fur.
2. Can a person’s genotype be determined by their phenotype? Why or why not? What is
the difference between genotype and phenotype?
No, because the phenotype (the observable traits) does not reveal the complete genetic
makeup. The genotype is the actual genetic code (the alleles present), whereas the
phenotype is the result of how those genes are expressed, often influenced by
dominance and environmental factors.
3. Are incomplete dominant and co-dominant patterns of inheritance found in human
traits? If yes, give examples of each.
Yes. In the ABO blood group system, the A and B alleles are co-dominant (producing AB
blood when both are present). An example of incomplete dominance in humans is less
common but may be observed in some cases of certain genetic disorders where
heterozygotes exhibit intermediate traits compared to homozygotes.
4. Consider the following genotype: Yy Ss Hh. We have now added the gene for height: Tall
(H) or Short (h).
a. How many different gamete combinations can be produced?
Each gene pair segregates independently. With three heterozygous gene
pairs, the number of gamete combinations is 2³ = 8.
b. Many traits (phenotypes), like eye color, are controlled by multiple genes. If
eye color were controlled by the number of genes indicated below, how many
possible genotype combinations would there be in the following scenarios?
5 Eye Color Genes: 243 combinations
, Lab 7 Mendelian Genetics BIO101L
10 Eye Color Genes: 59,049 combinations
20 Eye Color Genes: 3.49 billion combinations
