Question

When a pure tall pea plant (\textit{Pisum sativum}) with green pod is crossed with a dwarf pea plant with yellow pod, how many dwarf pea plants, out of 16, will be produced in the F\textsubscript{2 generation?}

• A. ( 9 )
• B. ( 3 )
• C. ( 4 )
• D. ( 1 )

Answer 1

The Correct Option is C

Let's denote the alleles as follows: Tall (T) is dominant over dwarf (t). Green pod (G) is dominant over yellow pod (g). The parental cross is TTGG (pure tall, green pod) × ttgg (dwarf, yellow pod). The F\textsubscript{1} generation will all be heterozygous: TtGg (tall with green pods). When the F\textsubscript{1} generation is self-crossed (TtGg × TtGg), the F\textsubscript{2} generation will have a phenotypic ratio of 9:3:3:1 for the four possible combinations of height and pod color (Tall, Green : Tall, Yellow : Dwarf, Green : Dwarf, Yellow). Out of 16 offspring in the F\textsubscript{2} generation, the proportion of dwarf plants will be the sum of the Dwarf, Green and Dwarf, Yellow phenotypes. The genotypes for dwarf plants are ttGG, ttGg, and ttgg. From a dihybrid cross, the probability of getting a dwarf plant (tt) is \( \frac{1}{4} \). Therefore, out of 16 plants, the number of dwarf plants will be \[ ( \frac{1}{4} \times 16 = 4 ). \]