Mendel's Law of Segregation: 1/2 of the gametes carry the dominant allele and 1/2 carry the recessive allele
Mendel's Law of Independent Assortment: alleles of different genes are sorted independently of each other during gamete formation
Genotype: genetic makeup of an individual (e.g., BB, Bb, bb)
Phenotype: physical characteristics of an individual (e.g., tall, short)
Dominant allele: will be expressed if an individual has one copy of the allele (e.g., B)
Recessive allele: will only be expressed if an individual has two copies of the allele (e.g., bb)
Homozygous: having two copies of the same allele (e.g., BB, bb)
Heterozygous: having one copy of each allele (e.g., Bb)
Monohybrid cross: cross between two parents that differ ∈ one trait
Dihybrid cross: cross between two parents that differ ∈ two traits
Test cross: cross between an individual of unknown genotype and a homozygous recessive individual
Chi-squared test: used to determine if the observed frequencies of a trait are significantly different from the expected frequencies
Hardy-Weinberg principle: p² + 2pq + q² = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele

🪤 The 5 Mistakes That Cost Marks

Not understanding the difference between genotype and phenotype
Not being able to apply Mendel's laws to solve problems
Not being able to calculate the probability of a particular genotype or phenotype
Not being able to distinguish between a monohybrid and dihybrid cross
Not being able to apply the Hardy-Weinberg principle to solve problems

✏️ 3 Solved PYQs

Question 1: A cross between two pea plants, one with the genotype BB and the other with the genotype bb, will produce offspring with what genotype and phenotype?
- Answer: The offspring will have the genotype Bb and the phenotype of the dominant allele (e.g., tall)
Question 2: A dihybrid cross between two parents that differ ∈ two traits, seed color and flower color, will produce offspring with what genotypes and phenotypes?
- Answer: The offspring will have a combination of the genotypes and phenotypes of the two parents, e.g., BbRr, Bbrr, bbRr, bbrr
Question 3: A test cross between an individual of unknown genotype and a homozygous recessive individual will produce offspring with what genotypes and phenotypes?
- Answer: The offspring will have a combination of the genotypes and phenotypes of the two parents, e.g., Bb, bb

🧠 The One Thing Most Students Get Wrong

Most students get the concept of independent assortment wrong, they think that the alleles of different genes are linked and will be inherited together, but ∈ reality, they are sorted independently of each other during gamete formation

👁️ Ayush's Note

To solve problems ∈ genetics, always start by identifying the genotypes and phenotypes of the parents and then use Mendel's laws to determine the probability of each genotype and phenotype ∈ the offspring
Use a Punnett square to visualize the possible genotypes and phenotypes of the offspring
Always check your answers using the Hardy-Weinberg principle

🔁 Last 5 Minutes Box

Review the formulas for Mendel's laws and the Hardy-Weinberg principle
Review the definitions of genotype, phenotype, dominant allele, and recessive allele
Practice solving problems using a Punnett square and the Hardy-Weinberg principle
Check your answers using the formulas and principles

📝 Practice MCQs

1. What is the genotype of an individual that is homozygous dominant for the trait of tallness?

A) Bb

B) BB

C) bb

D) BbRr

Answer: B) BB

2. What is the probability of an individual being tall if the genotype is Bb?

A) 1/2

B) 1/4

C) 3/4

D) 1

Answer: D) 1

3. What is the purpose of a test cross?

A) To determine the genotype of an individual

B) To determine the phenotype of an individual

C) To determine the frequency of a particular allele ∈ a population

D) To determine the probability of a particular genotype or phenotype

Answer: A) To determine the genotype of an individual

4. What is the Hardy-Weinberg principle?

A) p² + 2pq + q² = 1

B) p² - 2pq + q² = 1

C) p² + 2pq - q² = 1

D) p² - 2pq - q² = 1

Answer: A) p² + 2pq + q² = 1

5. What is the difference between a monohybrid and dihybrid cross?

A) A monohybrid cross involves one trait, while a dihybrid cross involves two traits

B) A monohybrid cross involves two traits, while a dihybrid cross involves one trait

C) A monohybrid cross involves one parent, while a dihybrid cross involves two parents

D) A monohybrid cross involves two parents, while a dihybrid cross involves one parent

Answer: A) A monohybrid cross involves one trait, while a dihybrid cross involves two traits

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This post was curated by Jules, Exam Compass Bot, and edited for accuracy by Ayush.

📚 Related Topics

Continue your revision with these related guides:

Mendel's Law of Segregation: 1/2 of the gametes carry the dominant allele and 1/2 carry the recessive allele
Mendel's Law of Independent Assortment: alleles of different genes are sorted independently of each other during gamete formation
Genotype: genetic makeup of an individual (e.g., BB, Bb, bb)
Phenotype: physical characteristics of an individual (e.g., tall, short)
Dominant allele: will be expressed if an individual has one copy of the allele (e.g., B)
Recessive allele: will only be expressed if an individual has two copies of the allele (e.g., bb)
Homozygous: having two copies of the same allele (e.g., BB, bb)
Heterozygous: having one copy of each allele (e.g., Bb)
Monohybrid cross: cross between two parents that differ ∈ one trait
Dihybrid cross: cross between two parents that differ ∈ two traits
Test cross: cross between an individual of unknown genotype and a homozygous recessive individual
Chi-squared test: used to determine if the observed frequencies of a trait are significantly different from the expected frequencies
Hardy-Weinberg principle: p² + 2pq + q² = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele