Question

Suppose Stephen breeds flowers and wants to optimize production of offspring with both short stems and white flowers, which are coded for by two genes with the recessive alleles t and p, respectively. In flowers, T codes for tall stems and P codes for purple flowers. Stephen crosses two heterozygotes that produce 544 offspring. How many of these 544 offspring are predicted to have both short stems and white flowers

Answer 1

Answer:

From the whole progeny of 544 plants, 34 individuals are expected to have short stems and white flowers.

Explanation:

Available data:

• short stems coded for by  recessive allele t
• white flowers coded for by recessive allele p
• T codes for tall stems
• P codes for purple flowers
• Cross between two heterozygous individuals
• Total number of the progeny 544

In a dihybrid cross, it is expected to get a phenotypic ratio of 9:3:3:1

Cross:

Parentals)     TtPp     x     TtPp

Gametes)  TP  Tp  tP  tp

                  TP  Tp  tP  tp

Punnett square)

        TP        Tp        tP        tp

TP   TTPP    TTPp   TtPP   TtPp

Tp   TTPp    TTpp   TtPp   Ttpp

tP    TtPP      TtPp    ttPP     ttPp

tp    TtPp     Ttpp     ttPp     ttpp

F1)

• 9/16 T-P-
• 3/16 T-pp
• 3/16 ttP-
• 1/16 ttpp  

(Note: The "-" symbol represents either a dominant allele or a recessive one)

From these possible genotypes and phenotypes, we can get their corresponding amount of individuals

16 ---------- 544 individuals

9 ------------X = 306 individuals tall stems and purple flowers T-P-

3-------------X = 102 individuals with tall stems and white flowers T-pp

3------------ X = 102 individuals with short stems and purple flowers ttP-

1 ------------ X = 34 individuals with short stems and white flowers, ttpp