Comprehension:
Mendelian genetics
Read the following passage carefully and answer the given questions.
In Mendel's monohybrid cross between pure tall (TT) and pure dwarf (tt) pea plants, the F1 generation consisted of all tall plants, including dominance of T over t. The tall and dwarf traits were identical to their parental type and did not show any blending. Selfing of F1 plants produced F2 generation in the ratio of 3 Tall: 1 dwarf, whereas genotypic ratio was 1TT : 2Tt : 1tt. Mendel concludes that alleles segregate during gamete formation and one allele from each parent is transmitted to offspring. Also, based on these observations, Mendel proposed that something was being stably passed down, unchanged, from parent to offspring through the gametes, over successive generations. He called these things as ‘factors’. Now we call them as genes as unit of inheritance. The production of gametes by the parents, the formation of the zygotes, the F1 and F2 plants can be understood from a diagram called Punnett Square.
Which one of the followings is a unit of inheritance?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Gene
Mendel found that something was passed unchanged from parents to offspring through the gametes. He called these things ‘factors’. They are now called genes, and the gene is the unit of inheritance. A gene carries the information needed to express a particular trait.
(1) Protein — Incorrect. A protein is a product that is made by following the information in a gene. It is not what parents pass on to the offspring.
(2) Allele — Incorrect. Alleles are the different forms of one gene, for example T and t for tall and dwarf. They are forms of the unit, not the unit itself.
(3) Chromosomes — Incorrect. Chromosomes are the structures that carry the genes. The gene, not the chromosome, is called the unit of inheritance.
(4) Gene — Correct. It is the unit of inheritance, the ‘factor’ of Mendel.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Inheritance of One Gene – “… Mendel proposed that something was being stably passed down, unchanged, from parent to offspring through the gametes, over successive generations. He called these things as ‘factors’. Now we call them as genes. Genes, therefore, are the units of inheritance.”