What is a balancer in Drosophila?

Balancer chromosomes are an essential and powerful part of a fly geneticist’s toolbox. They are used to maintain deleterious mutations in stable stocks as well as to prevent recombination and follow chromosomes in genetic mating schemes.

How do balancer chromosomes prevent recombination?

To suppress recombination, balancers usually harbor multiple, nested chromosomal inversions so that synapsis between the homologous chromosomes is disrupted. If crossing over does occur, it is often unbalanced, with each resulting chromatid lacking some genes and carrying two copies of others.

Is Mkrs a balancer?

are shown in the genotype. See Core Balancer Definitions for a description of the aberrations and markers defined by each balancer symbol used in the Bloomington stock list….Classical balancers.

Stock # Balancer Chr Genotype
3703 MKRS w[1118]/Dp(1;Y)y[+]; CyO/nub[1] b[1] sna[Sco] lt[1] stw[3]; MKRS/TM6B, Tb[1]

Why do you have to use virgin females in all D melanogaster crosses?

Virgin flies are needed to make sure that that the crosses are being appropriately made with the females using the desired sperms to fertilize their eggs. Female Drosophila are considered virgin eight to ten hours after they hatch from their pupa because during that time they are not receptive to male companionship and …

What is a deleterious mutation?

Listen to pronunciation. (DEH-leh-TEER-ee-us myoo-TAY-shun) A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder. When such a variant (or mutation) is inherited, development of symptoms is more likely, but not certain.

Why do female fruit flies have to be virgins?

Because female flies store sperm from previous matings before the eggs are fertilized, we only select virgin female flies for matings in order to ensure that every egg laid has the correct genotype.

What is the main difference between chromatin and chromosomes?

Chromatin is a complex formed by histones packaging the DNA double helix. Chromosomes are structures of proteins and nucleic acids found in the living cells and carry genetic material. Chromatin is composed of nucleosomes. Chromosomes are composed of condensed chromatin fibers.

Which is an example of a balancer chromosome?

There are numerous different balancers (with many variations) for each chromosome , named for the chromosome they stabilise. For example, in FM7i the F stands for first and the indicates it is multiply-inverted. Each carrying dominant mutations to make them obvious. Here are a couple of examples of markers, one for each chromosome.

What kind of mutation can be a balancer?

Any chromosome carrying at least one inversion and a closely linked recessive lethal or sterile mutation can function as a balancer for specific chromosomal regions.

Can a balancer chromosome contain multiple inverted sections?

This is particularly an issue if your gene of interest were to move to the other chromatid, when all your predictions assume it doesn’t. Balancer chromosomes typically contain multiple inverted sections and one or more marker genes.

How many balancer chromosomes does a Dmel have?

Balancer Chromosomes –. This change in eye shape is a dominant mutation in the gene Bar, and is the most prominent marker of first chromosome balancer, FM7, in adult flies. Dmel have four chromosomes, one (X/Y), two and three being important, four being rather small. There are two copies of each per normal cell.