In drosophila , short wings , and black colour are reccessive traits.long wings and grey colour are dominant. show the cross results between a short winged , heterozygous grey fly and a heterzygous long winged grey fly
To determine the cross results between a short-winged, heterozygous grey fly (Ss Gg) and a heterozygous long-winged grey fly (Ss Gg) in Drosophila, we can use a Punnett square.
First, let's write the genotypes of each parent:
- Short-winged, heterozygous grey fly (Ss Gg)
- Long-winged, heterozygous grey fly (Ss Gg)
The possible gametes these parents can produce are:
- Short-winged, heterozygous grey fly (Ss Gg) can produce the gametes: SG, sG, Sg, sg
- Long-winged, heterozygous grey fly (Ss Gg) can produce the gametes: SG, sG, Sg, sg
Next, we can create a 4x4 Punnett square to display the possible combinations of their gametes:
| SG | sG | Sg | sg |
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SG | SSGG | sSGG | SsGG | ssGG |
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sG | SSGg | sSGg | SsGg | ssGg |
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Sg | SSGg | sSGg | SsGg | ssGg |
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sg | SSGg | sSGg | SsGg | ssGg |
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Now let's analyze the results:
- Short-wings (recessive) will only be expressed if there is an "ss" genotype in the individual.
- Black color (recessive) will only be expressed if there is an "ss" genotype in the individual.
- Long-wings (dominant) will be expressed with either "SS" or "Ss" genotype.
- Grey color (dominant) will be expressed with either "GG" or "Gg" genotype.
From the Punnett square, we can calculate the phenotypic and genotypic ratios:
- Phenotypic ratio:
- Short-winged, grey (ssGG): 1/16
- Short-winged, black (ssGg): 3/16
- Long-winged, grey (S_G_): 9/16
- Long-winged, black (S_gg): 3/16
- Genotypic ratio:
- SS_G_: 1/16
- Ss_G_: 2/16
- ss_G_: 1/16
- SS_gg: 1/16
- Ss_gg: 2/16
- ss_gg: 1/16
Therefore, from this cross, there is a 1/16 chance of obtaining individuals with short wings and grey color, a 3/16 chance of obtaining individuals with short wings and black color, a 9/16 chance of obtaining individuals with long wings and grey color, and a 3/16 chance of obtaining individuals with long wings and black color.