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For summer squash, the dominant allele Y for gene 1 leads to yellow color while the recessive allele y leads to green color. Alleles of gene 2 can prevent color formation, with the dominant allele W leading to white squash while the recessive allele w does not interfere with color development. How many phenotypes would be observed among the offspring of the following cross: YyWw x YyWw

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marianaegarciaperedo

Answer:

Three phenotypes:

  • 12/16 individuals are expected to be white
  • 3/16 individuals are expected to be yellow
  • 1/16 individual is expected to be green

Explanation:

Available data:

  • Gene 1 → Dominant allele Y ⇒ yellow

                        Recessive allele y ⇒ green

  • Gene 2 → Dominant allele W ⇒ prevent color ⇒ White

                         Recessive allele w ⇒ Does not prevent color

Cross:

Parentals) YyWw        x     YyWw

Gametes) YW, Yw, yW, yw

                 YW, Yw, yW, yw

Punnett square)     YW          Yw           yW           yw

                YW      YYWW    YYWw     YyWW      YyWw

                 Yw      YYWw     YYww      YyWw      Yyww

                 yW      YyWW     YyWw      yyWW      yyWw

                 yw       YyWw      Yyww      yyWw      yyww

F1) Genotype

  • 1/16 YYWW
  • 2/16 YYWw
  • 1/16 YYww
  • 2/16 YyWW
  • 4/16 YyWw
  • 2/16 Yyww
  • 1/16 yyWW
  • 2/16 yyWw
  • 1/16 yyww

    Phenotype

  • 12/16 white individuals ⇒ Y-W-, yyW- (Dominant W allele is present, inhibiting the expression of color)
  • 3/16 yellow individuals ⇒ Y-ww (Dominant W allele is absent, so color can be expressed. Y allele determinates yellow color)
  • 1/16 green individuals ⇒ yyww (Dominant allele W is absent, so color can be expressed. Only y alleles are presents coding for green color)

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