🧬 Genetics Test Study Guide

⚠️ Test Coming Up!

Make sure you're prepared!

📋 What's on the Test:

  • 📚 Genetics Vocabulary
  • 🧬 Dominant vs. Recessive traits
  • 🔬 Genotype vs. Phenotype
  • 📊 Punnett Squares
  • 🔄 Mitosis vs. Meiosis
  • ⚠️ Mutations
  • 🔗 X-Linked Traits

📖 How This Works:

  1. 1. Read each section carefully
  2. 2. Answer the checkpoint question to prove you understood
  3. 3. Get it right to unlock the next section
  4. 4. Take the final quiz when you've completed all sections

Wrong answers give you hints - this is about learning, not just clicking through!

📚 Genetics Vocabulary

Why Vocabulary Matters

Before you can understand genetics, you need to know the language. These terms will appear throughout the test.

Study tip: Don't just memorize - make sure you can USE each word correctly.

🎴 Flashcards - Click to flip!

Click each card to see the definition. Try to say it yourself first!

🔒
Checkpoint: Prove You Know This!
Someone has genotype Bb. This means they have two DIFFERENT alleles.
What's the vocabulary word for "two different alleles"?
Homozygous
Phenotype
Heterozygous
Dominant

🧬 Dominant vs. Recessive Traits

What are Dominant and Recessive Traits?

Every trait you have is controlled by alleles - different versions of the same gene. You get ONE allele from mom and ONE from dad.

Dominant alleles are "stronger" - they SHOW UP even if you only have one copy. Written with a CAPITAL letter (like B).

Recessive alleles are "weaker" - they only show up if you have TWO copies. Written with a lowercase letter (like b).

Example: Eye Color

Brown eyes (B) is dominant. Blue eyes (b) is recessive.

BB = Brown eyes (two dominant)

Bb = Brown eyes (dominant wins!)

bb = Blue eyes (two recessive - the ONLY way)

Key point: Someone with Bb has brown eyes but CARRIES the blue eye gene!

Common Examples

Dominant (need 1):

  • Brown eyes
  • Dark hair
  • Widow's peak
  • Free earlobes

Recessive (need 2):

  • Blue/green eyes
  • Blonde/red hair
  • Straight hairline
  • Attached earlobes
🔒
Checkpoint: Lock It In!
If B = brown (dominant) and b = blue (recessive), what eye color does someone with genotype Bb have?
Brown eyes
Blue eyes
One brown, one blue
Green eyes

🔬 Genotype vs. Phenotype

Genotype = Your Genetic Code

Genotype is your genetic makeup - the actual alleles (letters) you have.

Examples of GENOTYPES: BB, Bb, bb, TT, Tt, tt

Always written as LETTERS

Memory trick: "Geno" sounds like "gene" → Genotype = the genes/letters

Phenotype = Physical Appearance

Phenotype is what you can actually SEE - the physical trait.

Examples of PHENOTYPES: Brown eyes, blue eyes, tall, short, curly hair

Describes what something LOOKS like

Memory trick: "Pheno" sounds like "physical" → Phenotype = physical appearance

The Connection

Your GENOTYPE determines your PHENOTYPE

BB → Brown eyes

Bb → Brown eyes

bb → Blue eyes

⚠️ Test Point: BB and Bb have the SAME phenotype (brown eyes) but DIFFERENT genotypes!

🔒
Checkpoint: Lock It In!
"Brown eyes" is an example of a:
Genotype
Phenotype
Chromosome
Allele

📊 Punnett Squares

What is a Punnett Square?

A Punnett Square shows all possible combinations of alleles offspring could inherit from two parents.

On the test you'll need to:

  • Fill in a Punnett square correctly
  • Calculate probabilities (like "25% chance of...")

How to Fill One In

  1. 1. Parent 1's alleles go across the TOP
  2. 2. Parent 2's alleles go down the LEFT SIDE
  3. 3. Fill each box: top letter + side letter
  4. 4. CAPITAL letter always goes first (Bb, not bB)

Example: Bb × Bb

B
b
B
BB
Bb
b
Bb
bb

Understanding Probabilities

Each box = 25% = 1/4 chance

From Bb × Bb:

  • 25% BB (1 box)
  • 50% Bb (2 boxes)
  • 25% bb (1 box)
  • 75% brown eyes, 25% blue eyes
🔒
Checkpoint: Lock It In!
In a Bb × Bb cross, what's the probability of getting a bb offspring?
50% (2 out of 4)
25% (1 out of 4)
75% (3 out of 4)
100%

🔄 Mitosis vs. Meiosis

Two Types of Cell Division

MITOSIS

Makes identical body cells

MEIOSIS

Makes sex cells (egg/sperm)

MITOSIS Details

Purpose: Growth & repair

Makes: 2 identical cells

Chromosomes: SAME number (46 → 46)

Variation: NONE - exact copies

MEIOSIS Details

Purpose: Make egg & sperm

Makes: 4 unique cells

Chromosomes: HALF (46 → 23)

Variation: YES - each cell different

Why half? Egg (23) + Sperm (23) = Baby (46)!

Venn Diagram

MITOSIS

  • • 2 cells
  • • Identical
  • • Body cells
  • • Same # chromosomes

BOTH

  • • Cell division
  • • DNA copies first
  • • Make new cells

MEIOSIS

  • • 4 cells
  • • Unique
  • • Sex cells
  • • Half chromosomes
🔒
Checkpoint: Lock It In!
Which type of cell division makes sex cells with HALF the chromosomes?
Mitosis
Meiosis
Both
Neither

⚠️ Mutations

What is a Mutation?

A mutation is a change in DNA - like a typo in genetic instructions.

Mutations are NOT always bad!

  • Harmful - causes problems
  • Neutral - no effect
  • Beneficial - gives advantage

Three Types of Mutations

DELETION

DNA is REMOVED

THE CAT ATE → THE _AT ATE

INSERTION

DNA is ADDED

THE CAT ATE → THE CAAT ATE

SUBSTITUTION

DNA is SWAPPED

THE CAT ATE → THE CAR ATE

🔒
Checkpoint: Lock It In!
A mutation where a piece of DNA is REMOVED is called a:
Insertion
Substitution
Deletion
Replication

🔗 X-Linked Traits

Sex Chromosomes

The 23rd chromosome pair determines biological sex:

XX

Female

XY

Male

X-Linked Traits

X-linked traits are controlled by genes on the X chromosome.

Examples:

  • Color blindness
  • Hemophilia

⚠️ Why Males Are Affected More - KEY TEST POINT!

Females (XX)

Need bad allele on BOTH X's to show trait

Can be carriers

Males (XY)

Only ONE X - if it has the allele, they show it

No backup X!

Remember: Males are more likely to have X-linked disorders because they only have ONE X chromosome!

🔒
Checkpoint: Lock It In!
Why are MALES more likely to show X-linked recessive traits like color blindness?
Males have two X chromosomes
Males only have ONE X chromosome - no backup
The Y chromosome causes the disorders
Females can't carry X-linked traits

✅ Final Practice Quiz

You've completed all sections! Now test yourself with this 10-question quiz.