Question

A sudden spontaneous change in structure and action of a gene is called
A. Variation
B. Allelomorph
C. Linkage
D. Mutation

Answer 1

A gene is the unit of DNA responsible for the appearance and inheritance of characters. The sum total of all genes inherited from parents, in an individual from the genotype. A gene pool is formed by all the genotypes of all organisms in a population.

Complete answer: Variation is the differences between the offspring and his parents. Offspring resembles their parents but they also vary from them. The resemblance is due to the genes inherited from their parents but all the genes don’t exhibit their phenotype. The genetic variation in sexually reproducing organisms develop because parental genes are shuffled into new combinations.
Linkage is the phenomenon in which the linked genes tend to go together in the same gamete as a result of which the parental combinations are obtained in greater frequency than expected in the progeny. It can also be defined as the co-existence of two or more genes or factors in the same chromosome as a result of which they are transmitted from one generation to another in groups called linkages. The degree or the strength of the linkage depends upon the distance between the linked genes in the chromosome.
Mendel used the term determiners, traits or factors for the differentiating characters like the dominant and recessive traits. The name allelomorph or allele to the pair of contrasting characters was proposed by Bateson, for example, the tall and dwarf form a pair of alleles.
The sudden and heritable change which is independent of the environment and liable to provide a permanent step of which evolutionary changes may be built, is called mutation. It can also be described as a sudden change in chromosomal DNA. The mutation can either be chromosomal or genetic mutation.
So, the correct answer is “Option D”.

Note: The two individuals having similar genotypes may become different in phenotype when they come into contact with different conditions of food, temperature, light, humidity and other external factors. This is called environmental variations.