Mendel’s laws

Gregor Mendel mainly used the garden pea plant, Pisum sativum, to investigate how contrasting traits are inherited. Peas were useful because they have clear observable features, a relatively short generation time, and can undergo self-pollination as well as controlled cross-pollination. Therefore option A is correct. Wheat, mango, and neem were not the principal organism associated with Mendel’s classic inheritance experiments.

The blending theory predicted that two parental traits would permanently mix, so a hidden trait should not reappear unchanged. Mendel crossed pea plants with contrasting traits and observed that the recessive dwarf trait disappeared in the F1 generation but reappeared in the F2 generation. This showed that hereditary factors remain discrete and are passed on separately. Therefore, option A is correct; B, C, and D contradict the actual observations.

Gregor Johann Mendel used the garden pea plant, Pisum sativum, to investigate how traits are inherited. Pea plants were suitable because they have several clear contrasting characteristics, a short generation time, and can undergo self-pollination as well as controlled cross-pollination. By comparing parental and offspring generations, Mendel identified regular patterns of inheritance. Therefore option A is correct; the other listed plants are not the classic organism used in his foundational experiments.

In a Mendelian cross, a dominant trait is expressed in the heterozygous first-generation offspring, whereas a recessive trait can remain hidden. Let T represent tallness and t represent dwarfness. A pure cross TT × tt produces F1 offspring with genotype Tt; because T is dominant, all F1 plants are tall. Therefore option A, tallness, is correct. Dwarfness is the contrasting recessive trait, and seed shape or colour is unrelated to this cross.

A monohybrid cross follows one pair of contrasting traits. For example, crossing two heterozygous plants, Tt × Tt, gives TT, Tt, Tt and tt in the second generation. Three offspring show the dominant trait and one shows the recessive trait, so the usual phenotypic ratio is 3:1. Therefore option A is correct. The other ratios do not represent the standard Mendelian phenotypic result.

The governing concept is Mendelian dominance. A dominant trait is expressed in the phenotype when its allele is present in either a homozygous or a heterozygous condition, so it can appear even when a contrasting recessive allele is also present. For example, Mendel observed tallness as dominant over dwarfness in pea plants. Therefore option A is correct; a dominant trait is not necessarily acquired and is not restricted to fossils.

Gregor Mendel is famous for establishing the basic laws of heredity through carefully controlled experiments with pea plants. By tracking contrasting traits across generations, he described predictable patterns of segregation and independent assortment. Thus option A is correct and Mendel is widely called the father of genetics. Darwin is chiefly associated with evolution by natural selection, while Newton and Einstein are known mainly for physics.

Mendel mainly used the garden pea plant, Pisum sativum, in his heredity experiments. Peas were suitable because they had several clear contrasting traits, a relatively short generation time, and could undergo self-pollination or controlled cross-pollination. Therefore option A is correct. Mango, wheat and neem were not the principal experimental plant associated with Mendel’s classic laws of heredity.

The governing concept is segregation of alleles in a monohybrid cross. If the F1 hybrids are Tt, the cross Tt × Tt produces TT, Tt, Tt and tt in a 1:2:1 genotypic ratio. Because TT and Tt are both tall while tt is dwarf, the phenotypic ratio is three tall plants to one dwarf plant, or 3:1. Therefore option A is correct.

In Mendel’s pea experiments, plant height was studied as a character with two clearly different forms: tall and dwarf. Such alternative forms of the same character are called contrasting traits. They are not identical, are not produced merely by practice or experience, and are not fossil traits. Hence option A correctly identifies the relationship between the two forms.

Mendel selected pea plants because they have several easily observable pairs of contrasting traits, such as tall versus dwarf stems and round versus wrinkled seeds. They also have a short generation time, produce many seeds, and can self-pollinate or be cross-pollinated under controlled conditions. Therefore option A gives the main reason. Pea plants reproduce and produce seeds, so options B and C are false.

The governing concept is Mendel’s law of independent assortment. During gamete formation, allele pairs for different traits can separate and arrange independently, provided the genes are not linked in a way that prevents this pattern. In a dihybrid cross, this produces combinations such as round-yellow and wrinkled-green as well as new combinations. Therefore A is correct; B states the opposite, while C and D confuse inheritance with reproduction.

The blending theory suggested that parental traits would permanently mix, like two colours of paint, so a recessive trait should not reappear unchanged. In Mendel’s pea experiments, a trait absent in the first hybrid generation reappeared in the second generation, such as dwarfness after crossing tall plants. This showed that hereditary factors remain distinct and can separate into later offspring. Hence option A is correct.

In a Mendelian cross, a dominant allele expresses its trait in a heterozygous offspring, whereas a recessive allele can remain masked. If a tall plant is crossed with a dwarf plant and every F₁ offspring is tall, the observed phenotype indicates that tallness is dominant under the usual pure-parent assumption. Dwarfness is therefore recessive, not destroyed. Options C and D contradict the observed F₁ result.

In a typical monohybrid cross, the parental alleles combine in F₁ so that the dominant phenotype is visible, while the recessive allele remains present but masked in a heterozygous genotype. During gamete formation and fertilisation, two recessive alleles may unite in an F₂ offspring, producing the recessive phenotype again, commonly in a 3:1 phenotypic ratio. Thus option A is correct.

The governing concept is the design of Mendelian inheritance experiments. Pea plants were useful because they have several clear, easily recognisable pairs of contrasting traits, such as tall/dwarf plants and yellow/green seeds. They also produce many offspring and can self-pollinate, while controlled cross-pollination is possible. These features allowed Mendel to compare parental traits and count their appearance in successive generations. Therefore option A gives the key reason.

In a Mendelian cross, contrasting forms of a trait are represented by different alleles. In a heterozygous first-generation offspring, one allele may mask the expression of the other. The expressed form is called dominant, while the hidden form is recessive. Therefore A, dominance, is correct. Evaporation, excretion and physical balance do not describe allele expression or Mendelian inheritance.

The prefix mono means one, so a monohybrid cross examines the inheritance of one contrasting pair of traits. The prefix di means two, so a dihybrid cross follows two contrasting pairs simultaneously, for example seed shape and seed colour. Therefore B is correct. A refers to only one trait, while C and D are different biological topics rather than types of Mendelian crosses.

A dihybrid cross follows two pairs of contrasting traits at the same time. Mendel’s results showed that, when the genes are not linked, the inheritance of one pair can occur independently of the inheritance of the other pair. This is the principle of independent assortment, so A is correct. Traits do not always travel together, and Mendel’s work supports inheritance of genetic factors rather than acquired traits.

Mendel’s principle of dominance explains why a dominant phenotype can mask a recessive one in the first filial generation. For example, an F1 plant with genotype Tt shows the dominant tall form, while the recessive allele t is still present in its genetic makeup. When alleles separate during gamete formation and combine again, the recessive phenotype can reappear in F2. Thus option A is correct; invisibility does not mean destruction or absence.