# The Drosophila FM7 - A Strain Contains a Fixed Translocation Involving the X and 4 Chromosomes

## TL;DR

This study reveals that the Drosophila FM7-A balancer chromosome is a translocation between chromosomes 1 and 4, which affects genetic experiments.

## Contribution

The discovery of a new translocation structure in the FM7-A balancer chromosome provides insights into its genetic behavior.

## Key findings

- FM7-A is a translocation involving chromosomes 1 and 4 with 5% of chromosome 1 material transferred.
- The chromosome 4 segregant is viable and fertile without the chromosome 1 segregant.
- The translocation structure may impact genetic experiments using this balancer chromosome.

## Abstract

We discovered that a commonly used balancer chromosome –
FM7-A, Tb
1
– exists as an uncharacterized translocation between the progenitor
FM7a
chromosome and a normal chromosome
4
. Genetic and cytological data evidence show that
T
(
1
;
4
)
FM7-A
translocates about 5% of chromosome
1
material to an entire chromosome
4
, thus the large “chromosome
1
” segregant is lethal without the small “chromosome
4
” segregant, though the latter is viable and fertile without the former. We characterize this balancer chromosome to inform
Drosophila
molecular-geneticists of the structure as it may affect their use of this balancer chromosome and the interpretations of their results.