Genetic inheritance and variations
Read the following passage carefully and answer the given questions.
While studying the pattern of inheritance in pea plants of contrasting characters, Mendel proposed the principles of inheritance, which are today referred to as ‘Mendel's Laws of Inheritance’. He proposed that some characters are dominant over others. The Punnett square can be effectively used to understand the independent segregation of the two pairs of genes during meiosis and the production of eggs and pollen in the plants. The pattern of inheritance of such Mendelian disorders can be traced in a family by the pedigree analysis. Most common and prevalent Mendelian disorders are Haemophilia, Cystic fibrosis, Sickle cell anaemia, Colour blindness, Phenylketonuria, Thalassemia, etc. It is important to mention here that such Mendelian disorders may be dominant or recessive. In Sickle cell anaemia the mutant haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in the shape of the RBC from biconcave disc to elongated sickle like structure. In thalassemia the formation of abnormal haemoglobin molecules resulting into anaemia which is characteristic of the disease. Thalassemia can be classified according to the affected chain of haemoglobin molecule.
Which one of the following parameters of Gregor Mendel's hybridization experiments, gave greater credibility to his data?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Large sampling size
(1) Microscopic analysis — Incorrect. Mendel did not use a microscope in his work. Chromosomes were observed only later.
(2) Large sampling size — Correct. Mendel studied a very large number of plants. With a large sample, chance effects cancel out and the ratios become reliable. His work was also the first in biology to use statistics and mathematical logic.
(3) Small sampling size — Incorrect. A small sample gives results that can change by chance. It would reduce credibility, not increase it.
(4) Molecular analysis — Incorrect. Nothing was known about DNA or genes as molecules in Mendel’s time.
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:
Mendel’s Laws of Inheritance – “… Mendel’s investigations into inheritance patterns it was for the first time that statistical analysis and mathematical logic were applied to problems in biology. His experiments had a large sampling size, which gave greater credibility to the data that he collected.”