Match the items in Column I with those in Column II and select the correctly matched option from those given b

Question

Q. Match the items in Column I with those in Column II and select the correctly matched option from those given below : Column I (Cross) 1. Mendelian monohybrid 2. Mendelian dihybrid 3. Incomplete dominance 4. Test cross (monohybrid) Column II (Phenotypic Ratio)

(i) 1 : 2 : 1 (F2)

(ii) 1 : 1

(iii) 3 : 1 (F2)

(iv) 9 : 3 : 3 : 1 (F2) Options : (A) 1–(ii), 2–(iv), 3–(i), 4–(iii) (B) 1–(iii), 2–(i), 3–(iv), 4–(ii) (C) 1–(iii), 2–(iv), 3–(i), 4–(ii) (D) 1–(ii), 2–(i), 3–(iv), 4–(iii)

CBSECBSE Class XII Board 2024MCQ· 1mImportance★★★★★

✓ Free question

Concept understanding — Mendelian Genetics Basics

Mendelian Genetics Basics

Imagine you have a box of coloured beads — red and white. If you pick one bead from the box, you get either red or white. Now imagine that the colour of your eyes, or the shape of your earlobe, is decided by something like that: a tiny "packet" inside your cells that comes in two versions, and you inherit one from each parent. That is the core idea of Mendelian genetics.

The everyday intuition

You have probably noticed that children often look like their parents — same hair colour, same dimples, same height. But they are never exact copies. Why? Because each parent contributes half of the "instructions" for building a child. Those instructions come in pairs, one from mother and one from father. Sometimes one instruction overrides the other; sometimes they blend. Gregor Mendel, a 19th-century monk, figured out the rules by watching pea plants — tall vs short, yellow vs green seeds — and counting what appeared in the next generation.

The precise meaning

Mendelian genetics is the study of how traits are passed from parents to offspring through genes. A gene is a unit of heredity — a stretch of DNA that codes for a specific characteristic, like flower colour. Each gene comes in different versions called alleles. For every gene, you inherit two alleles: one from your mother, one from your father.

If the two alleles are identical, you are homozygous for that trait. If they are different, you are heterozygous. In a heterozygous pair, one allele may be dominant — it shows up in the appearance — and the other recessive — it stays hidden unless both alleles are recessive.

Note

Mendel's key insight was that traits are not blended like paint. Instead, alleles remain separate and are passed on intact. A recessive allele can skip a generation and reappear later, unchanged.

Why it matters

Mendelian genetics is the foundation of modern biology. It explains:

Why some diseases run in families (like cystic fibrosis or sickle-cell anaemia)
How plant and animal breeders create new varieties
Why you might have your grandmother's eyes but not your mother's

The NCERT textbook states that Mendel's work established the laws of inheritance — the Law of Dominance, the Law of Segregation, and the Law of Independent Assortment. These laws describe how alleles separate during the formation of eggs and sperm, and how different genes are inherited independently of one another.

Key terms at a glance

Gene: a unit of heredity on a chromosome
Allele: a variant form of a gene
Dominant: the allele that expresses itself even when paired with a different allele
Recessive: the allele that expresses itself only when paired with an identical recessive allele
Homozygous: having two identical alleles for a gene
Heterozygous: having two different alleles for a gene
Genotype: the genetic makeup (e.g., Tt)
Phenotype: the observable trait (e.g., tall plant)

Important

In Mendelian genetics, the phenotype is determined by the genotype, but not every genotype produces a unique phenotype. A dominant allele masks the recessive one. So a plant with genotype TT (homozygous dominant) and a plant with Tt (heterozygous) both look tall — only the recessive tt looks short.

A final thought

Mendelian genetics is not about memorising a list of terms. It is about understanding that inheritance follows predictable patterns. Once you see that a single gene can have two versions, and that one can hide the other, you have the key to explaining countless patterns in nature — from the colour of a pea to the risk of a genetic disorder. That is why every biology textbook, including NCERT, begins here.

"Mendelian Genetics Basics: Definition, Terms & Real-World Examples" is exactly the kind of foundational topic students search for when starting the NCERT Class 12 Biology chapter on Principles of Inheritance and Variation. Because nearly every genetics question in CBSE boards and NEET builds on these basic terms — gene, allele, genotype, phenotype — mastering this page early makes the rest of the genetics unit far easier to revise.

This question asks us to match different types of genetic crosses with their characteristic phenotypic ratios. The key is to recall the expected ratios for Mendelian inheritance, incomplete dominance, and test crosses, leading to the correct option (C).

Understanding phenotypic ratios is fundamental to genetics. A phenotypic ratio describes the proportion of observable traits (phenotypes) among the offspring of a genetic cross. These ratios are determined by the type of inheritance (e.g., complete dominance, incomplete dominance) and the specific cross being performed.

Let's break down each type of cross and its expected phenotypic ratio.

1. Mendelian Monohybrid Cross (F2 Generation)

A Mendelian monohybrid cross involves tracking the inheritance of a single trait where one allele is completely dominant over the other. When two heterozygous individuals (F1 generation) are crossed, the F2 generation exhibits a characteristic phenotypic ratio.

Concept: Consider a trait like pea plant height, where 'T' (tall) is dominant over 't' (dwarf). If we cross true-breeding tall (TT) with true-breeding dwarf (tt) plants, the F1 generation will all be heterozygous tall (Tt). When these F1 individuals are self-pollinated or crossed with each other (Tt x Tt), the offspring genotypes will be 1 TT : 2 Tt : 1 tt.
Phenotypic Ratio: Due to complete dominance, both TT and Tt genotypes express the tall phenotype. Only tt expresses the dwarf phenotype. Therefore, the phenotypic ratio in the F2 generation is 3 Tall : 1 Dwarf.
Match: This corresponds to (iii) 3 : 1 (F2).

2. Mendelian Dihybrid Cross (F2 Generation)

A Mendelian dihybrid cross involves tracking the inheritance of two different traits simultaneously, assuming independent assortment and complete dominance for each trait.

Concept: Consider two traits, seed shape (R = round, r = wrinkled) and seed color (Y = yellow, y = green). If we cross true-breeding round, yellow (RRYY) with true-breeding wrinkled, green (rryy) plants, the F1 generation will all be heterozygous for both traits (RrYy). When these F1 individuals are self-pollinated or crossed with each other (RrYy x RrYy), the F2 generation will show a specific phenotypic distribution.
Phenotypic Ratio: According to Mendel's Law of Independent Assortment, the alleles for different traits segregate independently. This results in a phenotypic ratio of 9 Round, Yellow : 3 Round, Green : 3 Wrinkled, Yellow : 1 Wrinkled, Green.
Match: This corresponds to (iv) 9 : 3 : 3 : 1 (F2).

3. Incomplete Dominance (F2 Generation)

Incomplete dominance is a type of inheritance where neither allele is completely dominant over the other, resulting in a heterozygous phenotype that is intermediate between the two homozygous phenotypes.

Concept: A classic example is flower color in snapdragons, where 'R' (red) and 'W' (white) alleles result in 'RW' (pink) heterozygotes. If we cross true-breeding red (RR) with true-breeding white (WW) flowers, the F1 generation will all be pink (RW). When these F1 individuals are self-pollinated or crossed with each other (RW x RW), the offspring genotypes will be 1 RR : 2 RW : 1 WW.
Phenotypic Ratio: Because the heterozygous phenotype (pink) is distinct from both homozygous phenotypes (red and white), the genotypic ratio directly translates into the phenotypic ratio. Thus, the F2 phenotypic ratio is 1 Red : 2 Pink : 1 White.
Match: This corresponds to (i) 1 : 2 : 1 (F2).

4. Test Cross (Monohybrid)

A test cross is a specific type of cross used to determine the genotype of an individual expressing a dominant phenotype. This is done by crossing the individual with a homozygous recessive individual.

Concept: Suppose we have a pea plant that is tall (dominant phenotype), but we don't know if its genotype is homozygous dominant (TT) or heterozygous (Tt). We cross this plant with a homozygous recessive dwarf plant (tt).
- Case 1: If the tall parent is homozygous dominant (TT x tt): All offspring will be Tt (tall). The phenotypic ratio would be 1 Tall : 0 Dwarf.
- Case 2: If the tall parent is heterozygous (Tt x tt): The offspring will be 1 Tt : 1 tt. Phenotypically, this means 1 Tall : 1 Dwarf.
Phenotypic Ratio: The question implies the classic outcome of a test cross used to reveal heterozygosity, which yields a 1:1 ratio. If the unknown dominant individual is heterozygous, the test cross will produce offspring in a 1:1 phenotypic ratio.
Match: This corresponds to (ii) 1 : 1.

Summary of Matches:

Mendelian monohybrid (F2) → (iii) 3 : 1
Mendelian dihybrid (F2) → (iv) 9 : 3 : 3 : 1
Incomplete dominance (F2) → (i) 1 : 2 : 1
Test cross (monohybrid) → (ii) 1 : 1

Comparing these matches with the given options:

(A) 1–(ii), 2–(iv), 3–(i), 4–(iii)

(B) 1–(iii), 2–(i), 3–(iv), 4–(ii)

(D) 1–(ii), 2–(i), 3–(iv), 4–(iii)

The correct option is (C).

✓Final answer

The correctly matched option is (C), where 1-(iii), 2-(iv), 3-(i), and 4-(ii) are paired.

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

Showing the 12 most recent of 62 on this concept.

CBSE 2026Set EG1 mark
$Q. Who proposed the chromosomal theory of inheritance?$
›Reveal solutionSolution

The chromosomal theory of inheritance was put forward by Sutton and Boveri (1902).

Working independently, Walter Sutton and Theodor Boveri noticed that the behaviour of chromosomes during meiosis exactly parallels the behaviour of Mendel's 'factors' (genes) — they occur in pairs, segregate during gamete formation and assort independently. Around 1902 they proposed the chromosomal theory of inheritance, stating that genes are located on chromosomes, and that the pairing and separation of chromosomes is the physical basis of Mendel's laws. This linkage of genetics to chromosomes was later experimentally confirmed by T. H. Morgan through his work on Drosophila.

✓Final answer
$Walter Sutton and Theodor Boveri proposed the chromosomal theory of inheritance.$
CBSE 2026Set A1 markMCQ
$Q. Which of the following laws is based on monohybrid cross?$
(a) Law of dominance
(b) Law of segregation
(c) Law of independent assortment
(d) Both (A) and (B)
›Reveal solutionSolution

A monohybrid cross reveals the Law of Dominance and the Law of Segregation; independent assortment needs a dihybrid cross.

Mendel's monohybrid cross (a single-character cross) showed that one allele masks the other in the F1 (Law of Dominance) and that the paired factors separate during gamete formation so each gamete carries only one, reappearing in the 3:1 F2 ratio (Law of Segregation). The Law of Independent Assortment requires following two characters together (a dihybrid cross), so it is not based on a monohybrid cross.

✓Final answer
$(D) Both (A) and (B).$
CBSE 2026Set BOTANY1 markMCQ
$Q. The genotypic ratio of F2 generation of Mendel's monohybrid cross is _____.$
(a) 3 : 1
(b) 1 : 2 : 1
(c) 2 : 2
(d) 1 : 1
›Reveal solutionSolution
In a monohybrid cross, the F2 phenotypic ratio is 3:1 but the underlying genotypic ratio is 1:2:1.

In Mendel's monohybrid cross (e.g. tall (TT) x dwarf (tt) pea plants), the F1 generation is entirely heterozygous (Tt) and phenotypically tall, since tallness is dominant. When F1 plants are self-pollinated, each parent contributes either a T or a t gamete with equal probability (1/2 each). Using a Punnett square, the F2 offspring genotypes appear in the ratio:

TT (homozygous dominant) : 1/4

Tt (heterozygous) : 1/2 (i.e. 2/4, from Tt and tT)

tt (homozygous recessive) : 1/4

This gives a genotypic ratio of 1 TT : 2 Tt : 1 tt. Phenotypically, since both TT and Tt appear tall (T is dominant), the visible ratio collapses to 3 tall : 1 dwarf (the familiar 3:1 ratio). So the 1:2:1 ratio specifically describes the genotypes, while 3:1 describes the phenotypes.

✓Final answer
$(b) 1 : 2 : 1 - the F2 genotypic ratio of a monohybrid cross (1 homozygous dominant : 2 heterozygous : 1 homozygous recessive).$
CBSE 2026Set ANNUAL1 markMCQ
$Q. Who rediscovered the results of Mendel's inheritance of characters?$
(a) Devries, Correns and Tschermak
(b) Sutton and Boveri
(c) Schleiden, Schwann and Morgan
(d) Watson and Crick
›Reveal solutionSolution

Mendel's 1865 findings were ignored for about 35 years until three botanists independently rediscovered the same laws of inheritance in 1900.

Mendel presented his laws of inheritance in 1865, but their significance was not understood at the time and the work was ignored for about 35 years. In 1900, Hugo de Vries, Carl Correns and Erich von Tschermak independently rediscovered Mendel's results while working on different plants, and gave due credit to Mendel's original work. Sutton and Boveri later proposed the chromosomal theory of inheritance; Schleiden, Schwann and Morgan are associated with cell theory and the chromosomal basis of heredity, not the rediscovery; Watson and Crick worked out the DNA double helix structure.

✓Final answer
$(a) de Vries, Correns and Tschermak.$
CBSE 2026Set ANNUAL1 markMCQ
$Q. When the genotype of an organism contains two identical alleles, the organism is considered as$
(a) Homozygous
(b) Heterozygous
(c) Hemizygous
(d) Pleiotropy
›Reveal solutionSolution
Two identical alleles at a locus (e.g., TT or tt) make the organism homozygous; two different alleles (Tt) make it heterozygous.

In diploid organisms, each gene locus carries two alleles, one inherited from each parent.

If both alleles are identical (e.g., TT or tt), the genotype is homozygous (true-breeding) for that trait.

If the two alleles are different (e.g., Tt), the genotype is heterozygous.

Hemizygous refers to having only a single copy of a gene/allele (as with X-linked genes in a male, who has only one X chromosome).

Pleiotropy is when a single gene affects multiple, seemingly unrelated phenotypic traits — it is not a genotype description at all.

Since the question describes two IDENTICAL alleles, the correct term is homozygous.

✓Final answer
$(a) Homozygous.$
CBSE 2026Set ANNUAL1 markMCQ
$Q. Crosses between F1 offspring and either of their parents are called as$
(a) Inbreeding
(b) Back cross
(c) Dihybrid cross
(d) Test cross
›Reveal solutionSolution
A back cross is any cross of an F1 hybrid with one of its own parents; a test cross is the specific back cross to the homozygous recessive parent used to determine genotype.

Back cross: F1 offspring crossed with either parent (dominant homozygous OR recessive homozygous) — used generally in breeding programmes to study inheritance or improve stock.

Test cross: a specific type of back cross — F1 (of unknown genotype for a trait) crossed specifically with the homozygous recessive parent, used to determine whether the F1 is homozygous or heterozygous for the dominant trait.

Dihybrid cross involves tracking two traits simultaneously, unrelated to F1-to-parent crosses.

Inbreeding is mating between close relatives within the same breed/population, a broader concept, not specifically F1 × parent.

Since the question says 'either of their parents' (not specifically the recessive one), the general term is back cross.

✓Final answer
$(b) Back cross.$
CBSE 2026Set ANNUAL1 mark
$Q. ............. A cross between an organism of an unknown genotype and homozygous recessive organism.$
›Reveal solutionSolution

A test cross is a cross between an individual of unknown genotype and a homozygous recessive individual, used to determine whether the unknown individual is homozygous dominant or heterozygous.

In a test cross, an organism showing a dominant phenotype (whose genotype could be either homozygous dominant, e.g. TT, or heterozygous, e.g. Tt) is crossed with a homozygous recessive organism (tt). If all offspring show the dominant phenotype, the unknown parent was homozygous dominant; if the offspring segregate 1:1 (dominant : recessive), the unknown parent was heterozygous. This technique was used by Mendel to confirm his law of segregation.

✓Final answer
$Test cross.$
CBSE 2026Set ANNUAL1 markMCQ
$Q. A pure tall (TT) plant is crossed with a pure dwarf (tt) plant to produce F1 offspring. The F1 offspring are then self-crossed. What is the ratio of true-breeding tall (TT) to true-breeding dwarf (tt) plants in the F2 generation?$
(a) 1 : 1
(b) 1 : 2 : 1
(c) 1 : 3
(d) 3 : 1
›Reveal solutionSolution
The F2 of a monohybrid cross gives a 1 TT : 2 Tt : 1 tt genotypic ratio; the two true-breeding types (TT and tt) are therefore in a 1 : 1 ratio.

From the CBSE/NCERT Principles of Inheritance and Variation chapter (Mendel's monohybrid cross):

Parents: TT (tall) × tt (dwarf).

F1: all Tt (tall).

F1 selfed (Tt × Tt) gives the F2 Punnett square:

T t
T TT Tt
t Tt tt

Genotypic ratio = 1 TT : 2 Tt : 1 tt.

True-breeding tall = TT (1 part); true-breeding dwarf = tt (1 part).

So TT : tt = 1 : 1 (the 3 : 1 in option d is the phenotypic tall : dwarf ratio, not what is asked).

✓Final answer
$(a) True-breeding tall (TT) : true-breeding dwarf (tt) = 1 : 1.$
CBSE 2025Set 57/4/11 markMCQ
$Q. In a pea plant (Pisum sativum) inflated pod shape is dominant over constricted pod shape. The expected ratio of phenotypes of the offspring in a cross between both the parents with heterozygous inflated pod shape will be : (A) 1 : 0 (B) 1 : 1 (C) 2 : 1 (D) 3 : 1$
›Reveal solutionSolution
A cross between two heterozygotes (Ii × Ii) follows Mendel's monohybrid ratio: three offspring show the dominant phenotype (inflated) for every one showing the recessive (constricted). The answer is 3 : 1.

This is a classic Mendelian monohybrid cross. When both parents are heterozygous for a single trait, each carries one dominant and one recessive allele. The dominant allele masks the recessive in the phenotype, but the recessive can still be passed to offspring. The question tests whether you recognize the signature 3:1 phenotypic ratio that emerges when dominance is complete.

Let's denote the allele for inflated pod shape as I (dominant) and constricted pod shape as i (recessive). Both parents are heterozygous inflated, so their genotype is Ii.

Step-by-step analysis

Set up the cross

Parent 1: Ii (heterozygous inflated)

Parent 2: Ii (heterozygous inflated)

Determine the gametes

Each heterozygous parent produces two types of gametes in equal proportion: I and i.

Construct the Punnett square

Cross the gametes from both parents:

I (from Parent 2) i (from Parent 2)
I (from Parent 1) II Ii
i (from Parent 1) Ii ii

Identify the genotypes

The offspring genotypes are:

II : 1 (homozygous dominant)

Ii : 2 (heterozygous)

ii : 1 (homozygous recessive)

Genotypic ratio = 1 : 2 : 1

Determine the phenotypes

Since inflated (I) is dominant over constricted (i):

II → inflated pod

Ii → inflated pod (dominant masks recessive)

ii → constricted pod

Phenotypic ratio = 3 inflated : 1 constricted

$Heterozygous \times Heterozygous \to Phenotypic ratio 3:1$
Watch out

Don't confuse genotypic ratio (1:2:1) with phenotypic ratio (3:1). The question asks for phenotypes — what the pods look like, not the underlying genetic makeup.

✓Final answer
$The correct option is (D) 3 : 1 .$
CBSE 2025Set 57/4/11 markMCQ
$Q. Assertion (A) : ABO blood grouping in humans is an example of multiple allelism. Reason (R) : More than two genes in a population govern the same character in ABO blood grouping in humans.$
›Reveal solutionSolution
Multiple allelism means more than two alleles of a single gene exist in a population. ABO blood grouping is controlled by three alleles (I^A, I^B, i) of one gene, so Assertion is true. But the Reason says "more than two genes" — that is wrong; it's one gene with multiple alleles. Hence Assertion is true but Reason is false.

The core concept: What multiple allelism really means

When you hear "multiple alleles," the trap is to think it means "many genes." It does not. Multiple allelism refers to a single gene locus that has more than two possible allele variants present in the population. Any one diploid individual still carries only two alleles (one from each parent), but across the population, three or more different versions of that gene exist.

ABO blood grouping is the classic textbook example. The gene involved is the ABO gene on chromosome 9. It has three common alleles: I^A, I^B, and i. The I^A and I^B alleles are co-dominant (both expressed when together), and both are dominant over i. This gives the six possible genotypes and four blood group phenotypes you know.

Now look at the Reason statement carefully. It says: "More than two genes in a population govern the same character." That is a fundamental error. It is not "more than two genes" — it is more than two alleles of the same gene. The Reason misstates the definition of multiple allelism.

Step-by-step reasoning

Check the Assertion (A).

ABO blood grouping in humans is indeed an example of multiple allelism because three alleles (I^A, I^B, i) of a single gene exist in the human population. So Assertion is true.

Check the Reason (R).

The Reason says "more than two genes govern the same character." That is incorrect. In ABO blood grouping, only one gene (the ABO gene) governs the character. The multiple forms are alleles, not separate genes. So Reason is false.

Determine the relationship between A and R.

The Reason does not correctly explain the Assertion — it gives a wrong definition. Therefore, Assertion is true but Reason is false.

Watch out

A very common mistake in exams is to confuse "multiple alleles" with "polygenic inheritance." Polygenic traits (like skin colour or height) involve many different genes each contributing a small effect. Multiple allelism involves one gene with many allele variants. The Reason here describes polygenic inheritance, not multiple allelism.

Tip

A quick memory aid: Multiple alleles = one gene, many versions. Polygenic = many genes, one trait. ABO is the first; skin colour is the second.

✓Final answer
$The correct option is that Assertion (A) is true, but Reason (R) is false .$
CBSE 2025Set 57/5/11 markMCQ
$Q. During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in equal ratio. Find out the genotype of parent pea plants. (A) Tt \times tt (B) TT \times Tt (C) tt \times tt (D) Tt \times Tt$
›Reveal solutionSolution
The parent pea plants must have genotypes Tt (heterozygous tall) and tt (homozygous dwarf) to produce tall and dwarf offspring in an equal 1:1 ratio.

To understand the genotypes of the parent pea plants, we first need to recall the fundamental principles of Mendelian genetics, specifically concerning a monohybrid cross. A monohybrid cross involves studying the inheritance of a single pair of contrasting characters, such as plant height in pea plants. Gregor Mendel's experiments established that certain traits are dominant and others are recessive.

In pea plants, tallness is a dominant trait, while dwarfness is a recessive trait. This means that if an allele for tallness (let's denote it as 'T') is present, the plant will be tall, even if it also carries an allele for dwarfness. The allele for dwarfness (let's denote it as 't') will only express itself if two copies of it are present in the plant's genetic makeup.

Note

An allele is an alternative form of a gene. For instance, the gene for plant height has two alleles: 'T' for tall and 't' for dwarf.

A plant's genotype refers to its genetic constitution (the combination of alleles it possesses), while its phenotype is the observable characteristic (what it looks like).

For the trait of height in pea plants, the possible genotypes and their corresponding phenotypes are:

TT: Homozygous dominant, Phenotype: Tall

Tt: Heterozygous, Phenotype: Tall (because 'T' is dominant over 't')

tt: Homozygous recessive, Phenotype: Dwarf

We are given a monohybrid cross between a tall pea plant and a dwarf pea plant. The offspring population shows tall and dwarf plants in an equal ratio, meaning 1 tall plant for every 1 dwarf plant, or a 1:1 ratio. Our task is to determine the genotypes of the parent plants that would produce this specific offspring ratio.

Let's consider the dwarf parent first. Since dwarfness is a recessive trait, a pea plant can only be dwarf if its genotype is homozygous recessive, meaning it must have two copies of the dwarf allele.

Therefore, the genotype of the dwarf parent is tt.

Now, let's consider the tall parent. A tall pea plant can have one of two possible genotypes: TT (homozygous tall) or Tt (heterozygous tall). We need to test which of these, when crossed with a tt dwarf plant, yields a 1:1 ratio of tall to dwarf offspring.

Scenario 1: Tall parent is homozygous dominant (TT)

If the tall parent is TT, the cross would be TT × tt.

The TT parent produces only 'T' gametes.

The tt parent produces only 't' gametes.

When these gametes combine, all offspring will have the genotype Tt.

Since Tt plants are tall, all offspring would be tall.

The phenotypic ratio would be 100% Tall, or 1 Tall : 0 Dwarf. This outcome does not match the given 1:1 ratio of tall to dwarf offspring.

Scenario 2: Tall parent is heterozygous (Tt)

If the tall parent is Tt, the cross would be Tt × tt.

The Tt parent produces two types of gametes in equal proportion: 'T' and 't'.

The tt parent produces only 't' gametes.

Let's use a Punnett square to visualize the possible offspring genotypes:

t t
T Tt Tt
t tt tt

From the Punnett square, we can see the following offspring genotypes:

Two offspring are Tt. These plants will be Tall.

Two offspring are tt. These plants will be Dwarf.

The genotypic ratio is 1 Tt : 1 tt.

The phenotypic ratio is 1 Tall : 1 Dwarf.

This 1:1 ratio of tall to dwarf offspring perfectly matches the information given in the question. Therefore, the genotypes of the parent pea plants must be Tt and tt.

Important

A 1:1 phenotypic ratio in a monohybrid cross is characteristic of a test cross where one parent is heterozygous for the dominant trait and the other parent is homozygous recessive.

✓Final answer
$The genotypes of the parent pea plants are (A) Tt \times tt .$
CBSE 2025Set ANNUAL1 markMCQ
$Q. Number of chromosomes found in human beings is-$
(a) Four Pairs
(b) Twenty two pairs
(c) Twenty three pairs
(d) Twenty four pairs
›Reveal solutionSolution

A normal human somatic cell contains 23 pairs (46) of chromosomes.

Every normal human somatic (diploid) cell contains 46 chromosomes arranged as 23 homologous pairs — 22 pairs of autosomes and 1 pair of sex chromosomes (XX in females, XY in males). Gametes (sperm and ova) are haploid and carry only 23 chromosomes, one from each pair, so that fertilisation restores the diploid number of 46 in the zygote.

✓Final answer
$(iii) Twenty three pairs$

	I (from Parent 2)	i (from Parent 2)
I (from Parent 1)	II	Ii
i (from Parent 1)	Ii	ii

Q.Match the items in Column I with those in Column II and select the correctly matched option from those given below : Column I (Cross) 1. Mendelian monohybrid 2. Mendelian dihybrid 3. Incomplete dominance 4. Test cross (monohybrid) Column II (Phenotypic Ratio)

1. Mendelian Monohybrid Cross (F2 Generation)

2. Mendelian Dihybrid Cross (F2 Generation)

3. Incomplete Dominance (F2 Generation)

4. Test Cross (Monohybrid)

Summary of Matches:

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