Reverse Genetics Investigation Worksheet
9th Grade Biology • Genetics Practice
Backwards Genetics: Finding the Parents!
Look at the 4 kids to solve the mystery of who the parents are.
NAME:
DATE: PER:
Genotype The 2 letters (BB, Bb, bb)
Phenotype Physical look (Black or White)
Homozygous Same letters (BB or bb)
Heterozygous Different letters (Bb)
💡 The Golden Rule: Every child gets 1 letter from Mom and 1 letter from Dad!
★ Worked Example (How to Solve): Trait: Fur Color (B = Brown, b = White)
A scientist observes 4 bunny babies: Kid 1: Bb Kid 2: Bb Kid 3: bb Kid 4: bb (50% Brown, 50% White)
Parent 1 (Mom): Genotype: Bb | Phenotype: Brown
Zygosity: Heterozygous (different letters)
Parent 2 (Dad): Genotype: bb | Phenotype: White
Zygosity: Homozygous (same letters)
Why? Kid 3 is bb, so Mom gave one b and Dad gave one b. Kids 1 & 2 have a big B, which came from Mom!
Problem 1 • Pea Plant Height
T = Tall (Dominant) | t = Short (Recessive)
The 4 Offspring Plants Produced:
Plant 1: Tt (Tall) Plant 2: Tt (Tall) Plant 3: tt (Short) Plant 4: tt (Short)
Offspring Percentages: 50% Tall and 50% Short
Parent Plant 1:
Genotype (2 letters):
Phenotype (look):
Circle one: Homozygous | Heterozygous
Parent Plant 2:
Genotype (2 letters):
Phenotype (look):
Circle one: Homozygous | Heterozygous
Problem 2 • Fruit Fly Eye Color
R = Red eyes (Dominant) | r = White eyes (Recessive)
The 4 Offspring Flies Produced:
Fly 1: Rr (Red) Fly 2: Rr (Red) Fly 3: Rr (Red) Fly 4: Rr (Red)
Offspring Percentages: 100% Red-eyed (0% White-eyed)
Parent Fly 1 (Gave "R"):
Genotype: RR Phenotype: Red
Zygosity: Homozygous Dominant
Parent Fly 2 (Mystery Parent):
Genotype (2 letters):
Phenotype (look):
Circle one: Homozygous | Heterozygous
9th Grade Biology • Inclusion Genetics Practice Turn over for Page 2 (Level Up Challenge) ➔
Page 2 • Level-Up Backwards Practice
Identify the Alleles from the Clues!
Step 1: Write the 2 letters for each kid | Step 2: Find the parents!
Problem 3 • Labrador Puppy Coat Color
B = Black fur (Dominant) | b = Yellow fur (Recessive)
The 4 Puppies (Use the vocabulary clues to fill in the 2 letters for each puppy):
Pup 1 (Black) Homozygous Dominant
Letters:
Pup 2 (Black) Heterozygous
Letters:
Pup 3 (Black) Heterozygous
Letters:
Pup 4 (Yellow) Homozygous Recessive
Letters:
Offspring Percentages: 75% Black fur and 25% Yellow fur
Mom Dog:
Genotype (2 letters):
Phenotype (look):
Circle: Homozygous | Heterozygous
Dad Dog:
Genotype (2 letters):
Phenotype (look):
Circle: Homozygous | Heterozygous
Problem 4 • Guinea Pig Fur Texture
H = Hairy (Dominant) | h = Hairless (Recessive)
The 4 Guinea Pig Offspring (Fill in the 2 letters for each baby):
Baby 1 (Hairy) Heterozygous
Letters:
Baby 2 (Hairy) Heterozygous
Letters:
Baby 3 (Hairless) Homozygous Recessive
Letters:
Baby 4 (Hairless) Homozygous Recessive
Letters:
Offspring Percentages: 50% Hairy and 50% Hairless
Parent 1:
Genotype (2 letters):
Phenotype (look):
Circle: Homozygous | Heterozygous
Parent 2:
Genotype (2 letters):
Phenotype (look):
Circle: Homozygous | Heterozygous
✔ Quick Vocabulary Match (Draw a line to connect each word to its description)
1. Genotype
2. Phenotype
3. Heterozygous
• The physical appearance or what the organism looks like (e.g., Tall or Short)
• Having two different alleles/letters (e.g., Bb)
• The two-letter gene combination inherited from parents (e.g., BB, Bb, bb)
9th Grade Biology • Genetics Practice Page 2 of 2
