16.3: Lab Report

Introduction to Mendelian Genetics - Part 1

1. Use the letter ‘A’ to represent the following:
   • Homozygous dominant organism: _______________ Color: ____________________
   • Homozygous recessive organism: ________________ Color: ____________________
   • Heterozygous organism: _______________________ Color: ____________________

2. If the letter ‘A’ represents flower color, where ‘A’ represents red flowers and ‘a’ represents white flowers, what color would each flower be? Fill-in the blanks above.

3. Use Punnett Squares to calculate the expected genotypes and phenotypes of the offspring from the following crosses:

AA x aa AA x Aa

Aa x Aa (monohybrid cross) Aa x aa

4. Use Punnett Squares to calculate the expected genotypes and phenotypes of the offspring from the following crosses, if trait ‘A’ exhibits incomplete dominance:

AA x aa AA x Aa

Aa x Aa Aa x aa

5. Use Punnett Squares to calculate the expected genotypes and phenotypes of the offspring from the following monohybrid crosses, if traits ‘A’ and ‘B’ exhibit codominance:

AO x BO AO x OO

AA x BO BB x OO

Traits:

1. Bent little finger – bent is dominant “C”, straight is recessive “c” (clinodactyly)
2. Tongue rolling – tongue rolling is “R”, non-tongue rolling is “r”
3. Widow’s peak – V-shaped forehead hairline is “W”, straight forehead hairline is “w”
4. Free earlobe – free earlobes are “E”, attached earlobes are “e”
5. Finger hair – middle segment hair is “H”, no hair is “h”
6. Dimpled cheeks – dimples on one or both cheeks is “D”, dimple absence is “d”
7. Eyebrow raising – ability to raise eyebrows is “Y”, inability is “y”
8. Ear wiggling – ability to wiggle ears is “G”, inability is “g”
9. Long toe – if your second toe is longer than your big toe = “L”, a shorter second toe is “l”
10. Curly hair – curly hair is “A”, straight hair is “a”
11. Freckles – presence of freckles is “Z”, no freckles is “z”
12. PTC tasting – ability to taste is “P”, inability is “p” (phenylthiocarbamide)

Data Table for Student Genotypes and Phenotypes

Trait	Your Phenotype	Your Possible Genotype(s)	# Students Dominant Phenotype	# Students Recessive Phenotype	Class % Dominant Phenotype	Class % Recessive Phenotype
Bent little finger
Tongue rolling
Widow’s peak
Free earlobe
Finger hair
Dimpled cheeks
Eyebrow raising
Ear wiggling
Long toe
Curly hair
Freckles
PTC tasting

Number of students in our class: _________________

Introduction to Mendelian Genetics Part 2 – Dihybrid Cross

1. What are the possible combinations of alleles that may be found in the gametes of an organism that is heterozygous for both traits, ‘AaBb’? Remember that the gametes must have one allele for each trait: __________________________________________________________________
2. Use a Punnett square to calculate the expected genotypes and phenotypes of the offspring from the following dihybrid cross: AaBb x AaBb

Data Table for Dihybrid Cross

Gametes:

Expected genotypes and ratio: ____________________________________________________________

Expected phenotype and ratio: ___________________________________________________________