Genetics Decoder Workbook
Biology Inclusion Core
Genetics Decoder Workbook
Part 1: Key Terms & Allele Combinations
Name:
Date:
Period:
Reference Guide: The 6 Key Genetics Terms
Homozygous
"Homo" = SAME
Both alleles are identical in size.
BB or bb
Heterozygous
"Hetero" = DIFFERENT
One capital letter, one lowercase.
Bb
Dominant
The Strong Trait
CAPITAL letter. Always shows if present.
B
Recessive
The Hidden Trait
Lowercase letter. Needs 2 to show.
b
Genotype
GENE = Letters
The genetic code in letters.
GG, Gg, or gg
Phenotype
PHOTO = Looks
Physical appearance you can see.
Brown Fur, Tall
Section 1: Match the Term
Write the correct letter (A–F) in each box.
1. Genotype
2. Phenotype
3. Homozygous
4. Heterozygous
5. Dominant
6. Recessive
A. The physical trait or look you see (e.g. blue eyes).
B. Two identical alleles (such as TT or tt).
C. Strong allele that masks the weak one (capital letter).
D. The letter combination or genetic code (such as Bb).
E. Weak allele that hides unless paired with another small letter.
F. Two different alleles (one capital, one lowercase: Tt).
Section 2: Allele Identification Check
Write HO for Homozygous or HE for Heterozygous.
1. RR
2. Rr
3. bb
4. Tt
5. Aa
6. GG
7. ff
8. Mm
9. DD
10. Hh
11. ee
12. Yy
13. LL
14. pp
15. Ww
16. ZZ
Self-Check: Can an organism be "heterozygous recessive"? Explain why or why not:
Unit: Heredity & Genetics Page 1 of 6 Sheet 1: Front
Part 2
Genotype & Phenotype Translator
Sheet 1: Back
Trait Legend: Silly Monster Genetics
Body Fur Color
B = Purple Fur (Dominant) Capital B
b = Green Fur (Recessive) Lowercase b
Eye Number
E = Three Eyes (Dominant) Capital E
e = One Eye (Recessive) Lowercase e
Section 3: Words to Letters (Write the 2-Letter Genotype)
Use letters B/b or E/e.
1. Homozygous dominant (fur):
2. Heterozygous (fur):
3. Homozygous recessive (fur):
4. Purebred green fur:
5. Homozygous dominant (eyes):
6. Heterozygous (eyes):
7. Homozygous recessive (eyes):
8. Hybrid three eyes:
Section 4: Letters to Looks (Predict the Physical Phenotype)
Write what the monster looks like based on the genotype.
1. Genotype: BB
2. Genotype: Bb
3. Genotype: bb
4. Genotype: EE
5. Genotype: Ee
6. Genotype: ee
The Dominant Rule: If there is even ONE capital letter (like Bb or Ee), the dominant trait wins and is seen! The only way to see a recessive trait is having TWO small letters (bb or ee).
Unit: Heredity & Genetics Page 2 of 6 Sheet 1: Back
Part 3
Punnett Square Setup & Guided Practice
Sheet 2: Front
The 4 Steps to Solve Any Punnett Square
1. Identify
Find each parent's 2-letter genotype from the problem.
2. Set Up
Write Parent 1 alleles on top, Parent 2 on the left side.
3. Cross
Bring top letters down and side letters across into boxes.
4. Calculate
Each box is 25% (1/4). Count total genotypes and traits.
Practice Problem 1 T = Tall (Dominant) | t = Short (Recessive)
The Cross: A heterozygous tall plant is crossed with a short plant.
Parent 1: _____ Parent 2: _____
Fill outside letters & inside boxes
1. Parent 1 genotype (Heterozygous):
2. Parent 2 genotype (Short):
3. How many boxes have Tt?
4. How many boxes have tt?
5. Percentage of offspring that are Tall:
6. Percentage of offspring that are Short:
Practice Problem 2 B = Black Fur (Dominant) | b = White Fur (Recessive)
The Cross: Two heterozygous black guinea pigs mate.
Parent 1: _____ Parent 2: _____
Fill outside letters & inside boxes
1. Write Dad's genotype:
2. Write Mom's genotype:
3. How many boxes contain BB?
4. How many boxes contain Bb?
5. How many boxes contain bb?
6. Percentage with Black fur:
7. Percentage with White fur:
Unit: Heredity & Genetics Page 3 of 6 Sheet 2: Front
Part 4
Punnett Square Investigation 1 & 2
Sheet 2: Back
Investigation 1: Floppy Ears in Rabbits
Dominant: E (Straight) | Recessive: e (Floppy)
The Scenario: A rabbit breeder crosses a homozygous dominant straight-eared father rabbit with a homozygous recessive floppy-eared mother rabbit.
Dad: _____ Mom: _____
1. Dad's genotype (Homozygous Dominant):
2. Mom's genotype (Homozygous Recessive):
3. Genotype found inside all 4 boxes:
4. Percentage of babies with straight ears:
5. Percentage of babies with floppy ears:
Investigation 2: Dragon Fire Breath
Dominant: F (Fire Breath) | Recessive: f (Ice Breath)
The Scenario: A heterozygous fire-breathing dragon mates with an ice-breathing dragon.
Parent 1: _____ Parent 2: _____
1. Parent 1 genotype (Heterozygous):
2. Parent 2 genotype (Ice Breather):
3. Percentage that breathe Fire:
4. Percentage that breathe Ice:
5. Can two ice dragons produce a fire dragon?
Fraction to % Helper: 1/4 = 25% | 2/4 = 50% | 3/4 = 75% | 4/4 = 100%
Unit: Heredity & Genetics Page 4 of 6 Sheet 2: Back
Part 5
Punnett Square Investigation 3 & 4
Sheet 3: Front
Investigation 3: Pea Plant Seed Color
Dominant: Y (Yellow) | Recessive: y (Green)
The Scenario: A gardener crosses two pea plants that are both heterozygous yellow.
Plant 1: _____ Plant 2: _____
1. Plant 1 genotype (Heterozygous):
2. Plant 2 genotype (Heterozygous):
3. How many boxes contain yellow seeds?
4. Percentage chance of Yellow seeds:
5. Percentage chance of Green seeds:
Investigation 4: Cat Tail Length
Dominant: T (Long Tail) | Recessive: t (Short/Bobbed Tail)
The Scenario: A male cat that is homozygous dominant for a long tail mates with a female cat that has a short bobbed tail.
Dad: _____ Mom: _____
1. Dad's genotype (Homozygous Dominant):
2. Mom's genotype (Short Bobbed Tail):
3. Genotype found in all 4 boxes:
4. Percentage of kittens with Long tails:
5. Percentage of kittens with Short tails:
Genetics Rule: A trait described as "short" or "ice-breathing" is recessive, which means its genotype MUST have two lowercase letters!
Unit: Heredity & Genetics Page 5 of 6 Sheet 3: Front
Part 6
Genetics Detective Case & Mastery Check
Sheet 3: Back
The Mystery of the Golden Puppy
B = Black Coat | b = Golden Coat
The Crime Scene: A black mother dog (Bb) gives birth to a golden puppy (bb)! Two male dogs in the neighborhood could be the father:
Suspect 1: "Shadow"
Black fur, genotype BB
Suspect 2: "Rusty"
Black fur, genotype Bb
Cross 1: Mom (Bb) × Shadow (BB)
% Golden (bb):
Cross 2: Mom (Bb) × Rusty (Bb)
% Golden (bb):
Detective Verdict:
Which dog is the father?
Explain your genetic proof:
Final 5 Mastery Check
1. What is the physical appearance of an organism called? (A: Genotype | B: Phenotype)
2. Which of the following is heterozygous? (A: AA | B: Aa | C: aa)
3. How many recessive alleles are needed to show the recessive trait? (A: 1 | B: 2)
4. What percentage does each box in a 4-box Punnett square equal? (A: 25% | B: 50%)
5. In genotype Gg, which trait is physically displayed? (A: Dominant | B: Recessive)
How confident do you feel with genetics? Circle one number: 1 (Need Help) — 2 (Getting There) — 3 (I Got This!) — 4 (Genetics Pro)
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Unit: Heredity & Genetics Page 6 of 6 — Complete! Sheet 3: Back
