A pea plant's actual pair of alleles for flower colour is Aa. What term describes this Aa combination itself?

Genotype. The correct answer is Genotype. Genotype is the actual genetic makeup for a trait, written as a pair of alleles like Aa. Phenotype is the visible trait that results from it. Read more: GenSci0053 — Genetics Basics: Heredity, Traits and DNA.

Genetics Basics: Heredity, Traits and DNA

Curly hair, blood group, and eye colour all pass from parent to child. Chess skill does not, no matter how good a parent is at the game.

The difference is genetics. Some traits are written into our DNA and inherited directly. Others are simply learned. This topic explains how inherited traits actually get passed on.

A monohybrid Punnett square, crossing a homozygous dominant parent (AA) with a heterozygous parent (Aa). RobNobody, CC0/Public Domain, via Wikimedia Commons.

MCQ Questions

GenSci0053

0 to 1

The classic ratio Mendel found when crossing two heterozygous parents for one trait — three dominant offspring for every one recessive.

Genotype

The genes

An organism’s actual genetic makeup, e.g. Aa

Phenotype

The trait shown

The visible characteristic that results from the genotype

Dominant Allele

One copy is enough

Shows up even when paired with a recessive allele

Recessive Allele

Needs two copies

Only shows up when paired with another recessive allele

The exam angle: most PYQs test whether you can tell an inherited trait from a learned skill, or work out a genotype-to-phenotype ratio from a simple cross.

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📑 Contents

1Genotype, Phenotype and Alleles
2Mendel's Laws and the Punnett Square
3Test Yourself
4Chromosomes, DNA and Inherited vs Learned Traits
5Exam Point of View

🏛️ Must Know

Genotype, Phenotype and Alleles

Gene A gene is a segment of DNA that carries the instructions for one trait. It is passed from parent to offspring.
Allele An allele is one version of a gene. Most genes have two alleles, one inherited from each parent.
Genotype Genotype is an organism's actual genetic makeup for a trait, written as a pair of alleles, such as AA, Aa, or aa.
Phenotype Phenotype is the trait that is actually observed, such as flower colour or blood group. It results from the genotype.
Dominant vs Recessive A dominant allele shows up in the phenotype even with only one copy present. A recessive allele only shows up when both copies are recessive.

📘 Good to Know

Mendel's Laws and the Punnett Square

Law of Segregation Mendel's law of segregation says the two alleles for a trait separate during the formation of sex cells. Each offspring gets just one allele from each parent.
Law of Independent Assortment Mendel's law of independent assortment says alleles for different traits, on different chromosomes, are inherited independently of each other.
Punnett Square A Punnett square is a grid used to predict the possible genotypes of offspring from a cross between two known parents.
Classic 3:1 Ratio Crossing two heterozygous parents (Aa x Aa) for one trait gives offspring in a 3:1 ratio. Three show the dominant phenotype for every one that shows the recessive phenotype.
Carrier An organism with one dominant and one recessive allele is called a carrier. It shows the dominant trait but can still pass the recessive allele on.

Test Yourself

🌟 Great to Know

Chromosomes, DNA and Inherited vs Learned Traits

Chromosome A chromosome is a long, coiled strand of DNA carrying many genes. Humans have 23 pairs of chromosomes in almost every cell.
DNA DNA, deoxyribonucleic acid, is the molecule that stores genetic instructions. It sits inside the nucleus of a eukaryotic cell.
Inherited Traits Physical traits like curly hair, attached earlobes, freckles, and blood group are written into a person's genes. They are inherited directly from parents.
Learned Traits Skills like playing chess, speaking a language, or riding a bicycle are learned through practice. They are not passed on genetically, even if a parent is skilled at them.
The Key Test To tell the two apart, ask whether the trait exists in the body's genetic code or was built through experience. Only the first kind reliably passes to offspring.

📝 Exam Point of View

CDS I 2026 GK — Inherited vs Learned Traits

Question CDS I 2026 GK, Q6: a world chess champion has curly hair, attached earlobes, and freckles. Which trait is NOT likely to pass to his offspring? The correct answer is chess skill.
Why Curly hair, attached earlobes, and freckles are all genetic traits, written into the parent's DNA. Chess skill is a learned ability, built through years of practice, not carried in the genes.
Link See the full question, CDS I 2026 GK, Q6.

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