Question

Y-: yellow S-: star

Answer 1

Answer:

1. 120 individuals yySs
2. 60 individuals yyss

Explanation:

Available data:

• Two autosomal diallelic genes Y and S
• Y is the dominant allele that codes for yellow
• y is the recessive allele that expresses black
• S is the dominant allele that expresses stars
• s is the recessive allele that codes for starless
• Lethal genotypes: YYss and yySS

1st cross: A true-breeding yellow star bellied sneetch with a true-breeding black starless sneetch

Parentals)  YYSS   x   yyss

F1) 100% YySs

    N = 50

2nd Cross:

Parentals) YySs    x     YySs

Gametes) YS, Ys, yS, ys

                 YS, Ys, yS, ys

Punnett square)     YS        Ys        yS         ys

                     YS    YYSS   YYSs   YySS    YySs

                     Ys    YYSs    YYss    YySs    Yyss

                     yS    YySS     YySs    yySS   yySs

                     ys     YySs     Yyss    yySs    yyss

F1) N = 840

• 14/16 survivers
• 2/16 death YYss and yySS

• 9/16 yellow with stars
• 2/16 yellow starless Yyss
• 2/16 black with stars yySs      
• 1/16 black and starless, yyss

   

14 ------------------ 100% of the progeny --------------840 individuals

2 yySs -----------X = 14.28% ------------------------------X = 120 individuals yySs

1 yyss ------------X = 7.14% ------------------------------X = 59.97 individuals yyss

Answer 2

Answer:

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