Question

It is said that Mendel proposed that the factor controlling any character is discrete and independent. His proposition was based on the

• A. results of $F_3$ generation of a cross
• B. observations that the offspring of a cross made between the plants having two contrasting characters shows only one character without any blending
• C. self pollination of $F_1$ offsprings
• D. cross pollination of $F_1$ generation with recessive parent

Answer 1

Answer: (B)

When plants having two contrasting characters are crossed, $F_1$ generation shows dominant phenotype and the recessive phenotype is not lost but appears in $F_2$ generation. This suggested that there is no blending of Mendelian factors in $F_1$ generation but they stay together and only one of them is expressed. At the time of formation of gametes, these two factors obviously separate or segregate, otherwise recessive type will not appear in $F_2$ generation. The gametes which are formed are always pure for a particular character. That is why it is called as 'principle of segregation' or 'law of purity of gametes'.