# The underappreciated, underrecognized problem of fourth chromosome trisomy in Drosophila melanogaster stocks and a simple, general method for building diplo-4 stocks from triplo-4 stocks

## TL;DR

This paper addresses a common but overlooked issue in fruit fly genetics involving an extra fourth chromosome and offers a method to correct it.

## Contribution

A new method is introduced to identify and correct fourth chromosome trisomy in Drosophila stocks using a haploinsufficient gene mutation.

## Key findings

- Fourth chromosome trisomy is common in Drosophila stocks and can affect experimental results.
- A mutation in a haploinsufficient gene can be used to identify trisomic stocks.
- The method allows for the creation of disomic stocks from trisomic ones.

## Abstract

Trisomy of the small, fourth chromosome is common in
Drosophila melanogaster
stocks. Even though the presence of an extra chromosome can confound the interpretation of experimental crosses, many Drosophila geneticists are unaware of this potential problem. Here I describe a simple method employing a mutation in a haploinsufficient gene to recognize fourth chromosome trisomy and establish disomic stocks from trisomic stocks.