23. Which statement is true for Drosophila melanogaster?
(1) female are achiasmatic
(2) recombination does not occur during male meiosis
(3) recombination does not during female meiosis
(4) males show high frequency of recombination

The correct statement for Drosophila melanogaster is: (2) recombination does not occur during male meiosis.

Explanation of Each Option

1. Female are achiasmatic: This is false. In Drosophila melanogaster, females undergo normal meiotic recombination with chiasmata formation. They are not achiasmatic.

2. Recombination does not occur during male meiosis: True. Unlike females, male Drosophila melanogaster do not show meiotic recombination. Male meiosis is achiasmatic, meaning no crossing over or recombination occurs during spermatogenesis.

3. Recombination does not occur during female meiosis: False. Females exhibit normal crossing over and recombination during meiosis.

4. Males show high frequency of recombination: False. Males actually show no or very negligible recombination, which is a unique feature of Drosophila genetics.

Drosophila melanogaster, a model organism in genetics, exhibits a fascinating difference in recombination patterns between sexes. While females show typical recombination during meiosis, males uniquely undergo achiasmatic meiosis with no crossing over. This article explains these differences clearly and discusses why this phenomenon occurs.

Detailed Explanation

In Drosophila melanogaster, recombination between homologous chromosomes is confined to females. Female meiosis includes the formation of chiasmata and crossing over, which promotes genetic diversity. Conversely, male Drosophila meiosis is achiasmatic — meaning it lacks chiasmata and recombination events. This unusual trait leads to male offspring inheriting chromosomes without any exchange of genetic material.

Multiple studies confirm the absence of meiotic recombination in males, while females rely on recombination for proper chromosomal segregation. This sex-specific difference makes Drosophila a valuable system for studying genetic linkage, chromosome behavior, and mechanisms of segregation.

Each option in the original question addresses these genetic traits: option (2) is accurate because male Drosophila do not recombine, while options (1), (3), and (4) are misconceptions. Female flies are not achiasmatic; recombination occurs robustly in females, not males; and males do not exhibit high recombination frequencies.

This unique feature has implications for genetic mapping and evolutionary studies in fruit flies and highlights the diversity of meiotic processes in different organisms.