Question

How many pairs of chromosomes does a male Drosophila fly have? Which one of these bears the gene for eye color?

Answer 1

Hint: We know that there are two types of sex chromosome; the X and the Y type. These are used for determining the gender of an organism. Females have XX genotype where an X is inherited from the father. Males have XY genotype where they inherit a Y from father. Different organisms have different numbers of pairs of chromosomes.

Complete answer:
- Drosophila is commonly called fruit fly or vinegar fly that we daily see in our homes. The most common species of Drosophila are the Drosophila melanogaster.
- Eye color ranges from red to white depending upon the drosophila species and the genetic makeup.
- Drosophila just has four homologous pairs of chromosomes in which three are autosomes and one pair of sex chromosomes.
- X chromosome is responsible for the eye color in Drosophila. Here, the X chromosome does not directly pass from father to offspring of same sex but rather, it has a criss-cross pattern of inheritance and so it is transferred from one sex to the offspring of opposite sex.
- The white eye color trait is recessive here. Therefore its effect is seen in male because of only an X chromosome. Female flies will show white eye color trait when both X chromosomes carry recessive alleles for white color.

Note: Drosophila is a very well-known model organism for research purposes because of the following characteristics:
- These flies are easy to maintain and are not very big.
- They can be easily grown with minimal food requirements.
- They have a short life cycle and so their study becomes convenient.
- They have fewer chromosomes and so there are not as many complications.
- Their genome size is small.