Question

In a plant species, flower colour yellow is dominant over white, and fruit shape round is dominant over elongated. Crossing was performed between two pure lines-one having yellow-flower and round-fruit and another with white flower and elongated-fruit. About $20$ plants survived in $F_1$ progeny. Plants of $F_1$ were allowed to self-fertilize and about $960$ plants survived in $F_2$. If the traits follow Mendelian inheritance, the number of plants that would have yellow-flower and round-fruit in $F_1$ and $F_2$ are respectively ............ and ...............

• A. $20,960$
• B. $20,540$
• C. $10,160$
• D. $10,60$

Answer 1

Answer: (B)

$20,540$

In the given problem, yellow flower (Y) is dominant over white flower (y) and round fruit (R) is dominant over elongated fruit (r). If cross is made between two pure homozygous plants, that is YYRR x yyrr, the F${}_1$$generationwillhaveallyellowflowerwithroundfruit\left(YyRr\right).WhenplantsofF$_1$generationselffertilized,itwillproduceplantsintheratioof9:3:3:1,where9plantswillhaveyellowflowerwithroundfruits,3plantswillhaveyellowflowerwithelongatedfruits,3plantswillhavewhiteflowerwithroundfruits,and1plantwillhavewhiteflowerwithelongatedfruits.Hence,inF$_2$ generation, out of 960 plants, 960 * 9 / 16 = 540 plants will have yellow flower with round fruits.

Thus, the correct answer is option B.