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Suppose a species of tulip has three alleles for the gene that codes for flower color. The C R allele produces red tulips, the C p allele produces purple tulips, and the C w allele produces white tulips. C R is dominant over C p and C w , and C p is dominant over C w . For each cross, determine the expected phenotype ratio of offspring flower color.

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marianaegarciaperedo

Answer and Explanation:

Available data:

  • The Cr allele produces red tulips
  • The Cp allele produces purple tulips
  • The Cw allele produces white tulips.
  • Cr is dominant over Cp and Cw
  • Cp is dominant over Cw

Cross 1

Parental)        CrCp   x   CpCw

Gametes)    Cr   Cp      Cp   Cw

Punnet Square)     Cr          Cp

                      Cp  CrCp     CpCp

                      Cw  CrCw     CpCw

F1 phenotype ratio)

                    2/4=1/2  Red flowers, CrCp and CrCw

                    2/4=1/2  Purple flowers, CpCp and CpCw

Cross 2

Parental)        CrCw   x   CpCw

Gametes)    Cr   Cw      Cp   Cw

Punnet Square)     Cr          Cw

                      Cp   CrCp     CpCw

                      Cw  CrCw     CwCw

F1 phenotype ratio)

                   2/4=1/2  Red flowers, CrCp and CrCw

                    1/4 Purple flowers, CpCw

                   1/4 White flowers, CwCw

Answer: The expected phenotype ratio of cross between CR and Cp is 1:1:2.

1 for CC,

1 for Cp, purple

2 for CR and Rp(red) all which are offsprings from the cross.

For cross between Cp and Cw, phenotype ratio is 1:1:2.

1 for CC,

1 for Cw, white,

2 for Cp and pw,purple.

Explanation:

Phenotype gives the observable characters of an individual.

Here, the character observed is flower color of tulip species.

The expected phenotype ratio of cross between CR and Cp is 1:1:2. The offsprings from the cross are CC, Cp,CR and Rp

1 for CC,

1 for Cp, purple

2 for CR and Rp red, since red is dominant over purple.

For cross between Cp and Cw, phenotype ratio is 1:1:2. The offsprings from the cross give CC, Cw, Cp and pw

1 for CC,

1 for Cw, white,

2 for Cp and pw,purple since purple is dominant over white.

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