Posted: February 26th, 2023

White Eyed Trait in Drosophila melanogaster – Hypothesis and Prediction of Phenotypes for F2

White Eyed Trait in Drosophila melanogaster – Hypothesis and Prediction of Phenotypes for F2
Drosophila melanogaster, commonly known as the fruit fly, has been an important model organism in genetics for over a century. This tiny insect has a short life cycle, produces many offspring, and has a relatively small genome, making it an ideal organism for studying genetics. One of the most well-known traits in Drosophila is the white-eyed trait, which was first discovered by Thomas Hunt Morgan in 1910.

The white-eyed trait is a recessive trait that affects the color of the fly’s eyes. Normally, Drosophila have red eyes, but flies with the white-eyed trait have eyes that are white or light pink in color. The white-eyed trait is caused by a mutation in the gene that codes for the enzyme responsible for producing the red pigment in the eyes. When this gene is mutated, the enzyme cannot function properly, and the flies produce little or no red pigment in their eyes, resulting in the white-eyed phenotype.

In order to understand the inheritance of the white-eyed trait, we can use a Punnett square. If we cross two flies, one with white eyes and one with red eyes but carrying the white-eyed allele, we would expect the F1 generation to all have red eyes since the red-eyed allele is dominant. However, all of the F1 offspring would be heterozygous for the white-eyed allele since the white-eyed trait is recessive. When we cross two F1 heterozygotes, we can use a Punnett square to predict the phenotypes of the F2 generation.

The Punnett square for a cross between two F1 heterozygotes would look like this:

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The genotypic ratio for this cross would be 1:2:1, which means that for every four offspring, one would be homozygous dominant (red-eyed), two would be heterozygous (red-eyed carriers of the white-eyed allele), and one would be homozygous recessive (white-eyed).

The phenotypic ratio for this cross would be 3:1, which means that three out of every four offspring would have red eyes, and one out of every four offspring would have white eyes.

It’s important to note that the white-eyed trait is rare in natural populations of Drosophila. This is because the absence of red pigment in the eyes makes the flies less able to see, making them less likely to survive and reproduce. However, in laboratory populations where the flies are well-fed and protected from predators, the white-eyed trait can persist and be studied.

The white-eyed trait in Drosophila melanogaster is a recessive trait that affects the color of the fly’s eyes. It is caused by a mutation in the gene that codes for the enzyme responsible for producing the red pigment in the eyes. By using a Punnett square, we can predict the phenotypes of the F2 generation when two F1 heterozygotes are crossed. We would expect a phenotypic ratio of 3:1, with three out of every four offspring having red eyes, and one out of every four offspring having white eyes.