Sex Determination in Drosophila

Introduction

Despite the fact that both mammals and fruit flies generate XX females and XY males, their chromosomes do it in very distinct ways. Mammalian sex-determination systems differ significantly from those of insects like Drosophila.

In Drosophila, sex is determined by a balance of female X chromosome determinants and male autosome determinants. Flies normally have one or two sets of X chromosomes and 2 pairs of autosomes. The fly is male if there is just one X chromosome in a diploid cell (1X:2A). The fly is female if it has two X chromosomes in a diploid cell (2X:2A). XO Drosophila are, therefore, sterile males.

The Y chromosome does not play a role in determining sex in flies. Rather, it carries genes that help adults make sperm.

Table of Contents

• Drosophila melanogaster (Common Fruit Fly)
• Genome of D. melanogaster
• Sex Determination
• Frequently Asked Questions – FAQs

Drosophila melanogaster (Common Fruit Fly)

Drosophila melanogaster is a fly species of the Drosophilidae family, belonging to the Diptera taxonomic order. The fruit fly, also known as the lesser fruit fly, or the “pomace fly” or “vinegar fly”, is a frequent name for this species.

Mitotic and polytene chromosomes are the two primary types of chromosomes found in Drosophila, with dramatically different morphologies and biological functions. Polytene chromosomes are found in the interphase nuclei of differentiated cells, and are particularly prominent in the larval and adult ovarian tissues. In Drosophila, larval growth is predominantly achieved through endoreplication, which is the replication of the nuclear genome without mitosis, leading to increased nuclear gene content and polyploidy.

Genome of D. melanogaster

The genome of D. melanogaster (recorded in 2000 and edited at the FlyBase database) has four pairs of chromosomes: an X/Y pair and three autosomes. Apart from its critical eyeless gene, the fourth chromosome is rather tiny and thus typically overlooked. The genome of the D. melanogaster has been sequenced and annotated, and it comprises roughly 15,682 genes. More than 60% of the genome seems to be functional non-protein-coding DNA that regulates gene expression.

Over 60% of the genome seems to be active non-protein-coding DNA that regulates gene expression. In Drosophila, the X:A ratio of X chromosomes to autosomes is used to determine sex. Despite being fully heterochromatic, the Y chromosome consists of at least 16 genes, most of which are assumed to have male-specific activities.

Human-like Characteristics

According to a research published in March 2000 by the National Human Genome Research Institute analysing the fruit fly and human genomes, around 60% of genes are conserved across the two species. In the genome of fruit flies, 75% of genes known for the human disease have an identifiable match, and 50% of fly protein sequences possess mammalian homologs.

Drosophila has been utilised as a genetic model for a variety of human diseases, including Parkinson’s disease, Huntington’s disease, spinocerebellar ataxia, and Alzheimer’s disease. The fly has also been used to investigate the mechanisms underlying ageing and oxidative stress, as well as immunity, diabetes, cancer, and drug abuse.

Sex Determination

The sex chromosomes of the Drosophila melanogaster (fruit fly) have played a vital role in the comprehension of heredity. It might surprise you to learn that fruit flies utilise a somewhat unusual technique to determine sex. In Drosophila, the X:A ratio (ratio of the number of X chromosomes to the number of autosomes sets) is the most important factor in determining sex.

Which sex-specific transcription pattern is launched is determined by the equilibrium between female-determining proteins encrypted on the X chromosome and male-determining factors encrypted on the autosomes. Female flies are XX, XXY, and XXYY, whereas male flies are XY and XO.

All of the X chromosomes in Drosophila remain active, unlike in humans, and flies regulate the degrees of X-linked gene products by doubling expression from the X chromosome in males. An additional copy of the X chromosome, which carries nearly one-third of all fly genes, causes an aneuploid situation in which the cell’s balance is substantially disrupted.

In several other ways, Drosophila sex determination varies from mammalian sex determination. To begin with, sex determination occurs immediately after fertilisation, with no waiting period.

Furthermore, sex-specific features are not caused by hormones; rather, each cell in the embryo detects the X:A ratio and triggers either the female or the male-specific transcription sequence. According to microarray research, sex-specific gene expression differences are quite extensive. In fact, sex-specific expression biases were discovered in around 30% of Drosophila genes.

Related Links:

• Fly Life Cycle
• What Is Often Referred To As The Drosophila Of The Plant Kingdom?
• Why The Fruit Fly Drosophila Melanogaster Is Considered A Model Organism?