NEET UG Biology Heredity and Variation MCQs

GENE INTERACTION :-

Gene interaction is the modification of normal phenotypic expression of a gene due to either its alleles or non- allelic genes.

Gene interaction is of two types:-

   (i) Intragenic interaction

   (ii) Intergenic interaction

Intragenic interaction :-

In intragenic interaction , two alleles of a gene which are present on the same gene locus on the two homologous chromosomes ,react to produce modified phenotype.

Eq :- 1. Incomplete dominance

   2. Codominance

   3. Multiple alleles

Intergenic interaction :- It is the modified effect of a gene under the influence of a non - allelic gene.

Eq :- 1. Complementary genes

   2. Supplementary genes

Complementary genes :-

If two genes present on different loci produce the same effect when present alone but interact to form a new trait when present together are called complementary genes. Complementary gene ratio is 9 : 7

Supplementary Genes :- 

Supplementary genes are two non allelic genes in which one type of gene produces its effect whether the other is present or not and the second gene produces its effect only in the presence of the first, usually forming new trait. Supplementary gene ratio is 9 : 3 : 4

INHERITANCE :-

There are two types of inheritance

1. Qualitative inheritance / Monogenic inheritance

2. Quantitative inheritance / polygenic inheritance

Monogenic inhenitance :-

* A single dominant gene inflences a complete trait.

* Intermediate forms are not produced

Polygenic inheritance :-

* Full trait is shown when all dominant alleles present.

*Each dominant allele expresses a part or unit of the trait.

* Intermediate forms are produced

Ex:- Human skin colour

VARIATIONS :-

* Variations are differences found in morphological, physiological, Cytological and behavioural traits of individuals belonging to same species.

* Hereditary variations are transmitted from generation to generation where as environmental variations are temporary and do not relate with last or next generation.

M.C.Q.