Match List-I with List-II.
| List-I | List-II |
| A. Multiple alleles | I. Physical association of genes on a chromosome |
| B. Test cross | II. ABO blood grouping in humans |
| C. Incomplete dominance | III. Flower colour in snapdragon (Antirrhinum) |
| D. Linkage | IV. A plant with the dominant phenotype crossed with the recessive parent |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-IV, C-III, D-I
(A) Multiple alleles — this matches (II) ABO blood grouping in humans. The ABO blood groups are controlled by the gene I, which has three alleles, IA, IB and i. More than two alleles of one gene governing the same character is called multiple allelism.
(B) Test cross — this matches (IV) A plant with the dominant phenotype crossed with the recessive parent. A plant showing the dominant trait may be TT or Tt. Crossing it with the recessive parent shows its genotype from the offspring.
(C) Incomplete dominance — this matches (III) Flower colour in snapdragon (Antirrhinum). A cross of red (RR) and white (rr) snapdragons gives pink F1 plants (Rr), a colour in between the two parents.
(D) Linkage — this matches (I) Physical association of genes on a chromosome. Morgan used the term linkage for genes that lie on the same chromosome and tend to be inherited together.
NCERT Extract:
Co-dominance – “… ABO blood groups are controlled by the gene I. … The gene (I) has three alleles IA, IB and i. … Here you can see that there are more than two, i.e., three alleles, governing the same character. Since in an individual only two alleles can be present, multiple alleles can be found only when population studies are made.”
Inheritance of One Gene – “… In a typical test cross an organism (pea plants here) showing a dominant phenotype (and whose genotype is to be determined) is crossed with the recessive parent instead of self-crossing.”
Incomplete Dominance – “… The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance.”
Linkage and Recombination – “… Morgan attributed this due to the physical association or linkage of the two genes and coined the term linkage to describe this physical association of genes on a chromosome and the term recombination to describe the generation of non-parental gene combinations (Figure 4.11).”