Homozygous recessive with two white encoding alleles – genotype XwXw ; phenotype white eyes.
What is the only possible genotype of a white-eyed male?
Like humans, Drosophila males have an XY chromosome pair, and females are XX. In flies, the wild-type eye color is red (XW) and it is dominant to white eye color (Xw) (Figure 1). Drosophila males lack a second allele copy on the Y chromosome; that is, their genotype can only be XWY or XwY .
What is the genotype of a white eye female fly?
Genotypes and phenotypes of offspring if the female is heterozygous. Half of the male and half of the female offspring of a heterozygous female would be white-eyed; the other half would be red-eyed. Therefore the female must be a heterozygous, X w+ X w .
What color eyes would a fly with the genotype RR have?
The cross is between a red-eyed fruit fly and a white-eyed (rr) fruit fly. The only way an offspring can have white eyes, is if it inherited a recessive allele from both parents. The gene for eye color in fruit flies is actually sex-linked on the X-chromosome.
What is white eye mutation in Drosophila?
white, abbreviated w, was the first sex-linked mutation discovered , found in the fruit fly Drosophila melanogaster. In 1910 Thomas Hunt Morgan and Lilian Vaughan Morgan collected a single male white-eyed mutant from a population of Drosophila melanogaster fruit flies, which usually have dark brick red compound eyes.
Can female flies have white eyes?
All of the females and all of the males will have red eyes. All of the females will have white eyes ; half of the males will have red eyes, and half of the males will have white eyes.
Why do some flies have white eyes?
They have a defect in their “white” gene , which normally produces the red pigments in the eye. In these flies, the white gene only works partially, producing fewer red pigments than it should. These flies have white eyes.
What percent of males will have red eyes?
probability of getting red-eyed males? (You must include the probability of getting males AND red eyes). Step 5: One out of four ( 25% of) offspring will be both inale, and have red eyes.
What is the chance that the offspring will have white eyes?
What is the chance that there will be an offspring with white eyes? 50% or 244 Page 2 6. Hemophilia is a disease caused by a gene found on the X chromosome. Therefore, it is referred to as a sex-linked disease.
Do white eyed males inherit the allele for white eyes from their father or their mother?
Thus all female progeny will have red eyes due to the dominant red allele they inherit from the father, and all male progeny will have white eyes due to the white allele on the X chromosome they inherit from the mother .
Can two brown eyes make blue eyes?
If both of you have brown eyes, then there is generally a 25% chance that the baby will have blue eyes if both of you carry the recessive blue-eye gene. But if only one of you has a recessive blue-eye gene, and the other has two brown, dominant genes, then there is a less than 1% chance of the baby having blue eyes .
What is a reason for doing a test cross?
A test cross is a way to explore the genotpye of an organism . Early use of the test cross was as an experimental mating test used to determine what alleles are present in the genotype.
What is the genotype of the blue eyed female parent?
In our example, this genotype is written Bb . Finally, the genotype of an organism with two recessive alleles is called homozygous recessive. In the eye color example, this genotype is written bb. Of these three genotypes, only bb, the homozygous recessive genotype, will produce a phenotype of blue eyes.
Are red or white eyes dominant in Drosophila?
Red eye color is wild-type and is dominant to white eye color . Eye color in Drosophila was one of the first X-linked traits to be identified. Thomas Hunt Morgan mapped this trait to the X chromosome in 1910. Like humans, Drosophila males have an XY chromosome pair, and females are XX.
What gene is mutated in white eye flies?
The Drosophila gene w (CG2759) is a central part of the eye-pigmentation pathway. It encodes an ATP binding cassette transporter, White (O'Hare et al., 1984; Pepling and Mount, 1990), that forms dimers with either Brown or Scarlet proteins, encoded by brown and scarlet genes respectively.
What does the white gene do in Drosophila?
The white (w + ) gene in Drosophila, discovered in 1910 by Thomas Hunt Morgan 16 , encodes a subunit of an ATP-binding cassette (ABC) transporter , which loads up pigment granules and deposits the content to pigment cells in the compound eyes, ocelli, Malpighian tubules and testis 17 , 18 .
