Q.If a plant has genotype AaBb, what will be the possible number of gametes it may produce?
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Mendel's Law of Independent Assortment
Imagine you are packing two different suitcases for a trip. One suitcase is for clothes, the other for books. How you arrange the shirts inside the clothes suitcase has nothing to do with how you stack the books in the book suitcase. The two packing jobs happen independently.
That is the core intuition behind Mendel's Law of Independent Assortment. It says that when an organism passes on its genes to its offspring, the inheritance of one trait (like seed colour) does not influence the inheritance of another, separate trait (like seed shape). Each trait gets its own "lottery ticket" during reproduction, and the tickets are drawn separately.
The precise meaning
Gregor Mendel, working with pea plants in the 19th century, noticed that certain pairs of characteristics — for example, seed colour (yellow or green) and seed shape (round or wrinkled) — were inherited completely independently of each other. A plant could pass on a yellow colour gene and a wrinkled shape gene together, or a green colour and a round shape, or any combination. The chance of getting a particular colour was always 50-50 (in a certain cross), and the chance of getting a particular shape was also 50-50, and these chances did not affect each other.
The Law of Independent Assortment applies only to genes that are located on different chromosomes (or very far apart on the same chromosome). If two genes are on the same chromosome, they tend to be inherited together — that is called linkage, and it is an exception to this law. NCERT textbooks clearly state this limitation.
Why it matters
This law explains the enormous variety we see in living things. Because traits are shuffled independently, a single pair of parents can produce offspring with many different combinations of characteristics. For a human student, think of it this way: your eye colour and your hair colour are not tied together by fate. You could have your mother's eyes and your father's hair, or vice versa, or a mix. Independent assortment is one of the main reasons siblings (except identical twins) look different from each other.
In the NCERT Class 12 Biology textbook, Mendel's Law of Independent Assortment is stated as:
"When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters."
This means that during the formation of eggs and sperm (gametes), the alleles (versions of a gene) for one trait separate into gametes without being influenced by the alleles for another trait.
A few key points to remember
- It is the second law Mendel discovered (the first is the Law of Segregation, which says each organism has two copies of each gene and passes one copy randomly to offspring).
- It explains why a dihybrid cross (a cross involving two traits) yields a 9:3:3:1 ratio of offspring types — but you do not need to memorise that ratio for a prose subject. …
The number of distinct gamete types a heterozygous individual can produce follows a simple rule tied to how many gene pairs are heterozygous and assort …
Number of gamete types = 2ⁿ, where n = number of heterozygous gene pairs. For AaBb, n = 2, so 2² = 4 gamete types.
A plant with genotype AaBb is heterozygous at two independently assorting gene loci (A/a and B/b). During meiosis, each gene pair segregates independently (Law of Independent Assortment), and the alleles combine randomly into gametes. The possible combinations are:
AB, Ab, aB, ab
…
- CBSE 2026Set A1 markMCQQ.How many types of gametes would be formed if the genotype of plant is AaBbCc?(a) Two(b) Four(c) Eight(d) Sixteen
›Reveal solutionSolution
Number of gamete types = 2^n where n = number of heterozygous gene pairs; here n = 3, so 2^3 = 8.
Each heterozygous gene pair segregates independently during meiosis, giving 2 kinds of gamete for that gene. For AaBbCc there are 3 heterozygous pairs, so the total numb …
- CBSE 2026Set ANNUAL1 markMCQQ.If a plant has genotype AaBb, what will be the possible number of gametes it may produce?(a) 1(b) 2(c) 3(d) 4
›Reveal solutionSolution
Number of gamete types = 2ⁿ, where n = number of heterozygous gene pairs. For AaBb, n = 2, so 2² = 4 gamete types.
A plant with genotype AaBb is heterozygous at two independently assorting gene loci (A/a and B/b). During meiosis, each gene pair segregates independently (Law of Independent Assortment), and the alleles combine randomly into gametes. The possible combinations are:
AB, Ab, aB, ab
…
- CBSE 2024Set E1 markMCQQ.What is the cytological basis of law of independent assortment?(a) There is no blending of alleles(b) Alleles of a pair separate during gamete formation(c) Alleles may be dominant or recessive(d) Pair of chromosomes arrange themselves in line independently in metaphase I
›Reveal solutionSolution
Independent assortment is explained cytologically by the random, independent alignment of different homologous chromosome pairs at metaphase I of meiosis.
Mendel's law of independent assortment states that the alleles of two different genes assort independently of one another during gamete formation. The chromosomal (cytological) explanation is:
- During metaphase I of meiosis, the homologous pairs of chromosomes line up at the equator INDEPENDENTLY of one another.
- Which member of one pair goes to a given pole is independent of the orientation of any other pair. …
- CBSE 2023Set ANNUAL1 markQ.How many different types of genetically different gametes will be produced by a heterozygous plant having genotype AaBbCcDd?
›Reveal solutionSolution
For n heterozygous, independently assorting gene pairs, the number of distinct gamete types is 2ⁿ.
According to Mendel's Law of Independent Assortment, each pair of alleles segregates and assorts into gametes independently of the other pairs (for genes on different chromosome pairs). If an individual is heterozygous at n such gene loci, the number of genetically distinct gamete types it can produce is 2ⁿ. Here the plant AaBbCcDd is heterozygous …
- CBSE 2023Set ANNUAL1 markMCQQ.Variations are revealed during meiosis(a) due to crossing over(b) due to independent assortment(c) due to linkage(d) both(a) and (b)
›Reveal solutionSolution
Meiotic variation comes from crossing over AND independent assortment.
Meiosis introduces genetic variation in two main ways. (1) Crossing over during pachytene of prophase-I exchanges segments between homologous chromosomes, producing new allele combinations on a chromosome (recombination). (2) Independent assortment: homologous pairs orient randomly at metaphase-I, so maternal and paternal chromosomes are distributed to gametes in many differ …
- CBSE 2018Set ANNUAL1 markQ.Which Mendel's law is based on dihybrid cross? Write its name.
›Reveal solutionSolution
The dihybrid cross is the basis of Mendel's Law of Independent Assortment (his Third Law).
Concept
In a dihybrid cross two pairs of characters are studied together — for example seed shape (round/wrinkled) and seed colour (yellow/green) in pea. Mendel crossed pure round-yellow (RRYY) with wrinkled-green (rryy) plants; the F2 generation showed the famous 9 : 3 : 3 : 1 phenotypic ratio.
Why this proves independent assortment …
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