Genetic balancers are genetic constructs or chromosomal rearrangements that allow lethal or sterile mutations to be stably maintained in heterozygotes. In this chapter we use the term balancer primarily to refer to chromosomal duplications or rearrangements that suppress crossing over.

What is a genetic balancer?

Genetic balancers are genetic constructs or chromosomal rearrangements that allow lethal or sterile mutations to be stably maintained in heterozygotes. In this chapter we use the term balancer primarily to refer to chromosomal duplications or rearrangements that suppress crossing over.

What are the three main properties of balancer chromosomes?

Typical balancer chromosomes are designed to (1) carry recessive lethal mutations themselves, eliminating homozygotes which do not carry the desired mutation; (2) suppress meiotic recombination with their homologs, which prevents de novo creation of wild-type chromosomes; and (3) carry dominant genetic markers, which …

Is CyO a balancer?

For example, CyO is probably the most popular second chromosome balancer, but it does a poor job maintaining mutations near the chromosome ends, because its distal most breakpoints are in 22D and 58B. Recombination distal to these breakpoints is reduced, but crossovers still occur.

What is balancer Drosophila?

Balancer chromosomes are multiply inverted and rearranged chromosomes that are widely used in Drosophila genetics. First described nearly 100 years ago, balancers are used extensively in stock maintenance and complex crosses.

Is homozygous CyO lethal?

The DTS/DTS and CyO/CyO are both recessive lethal, so you have successfully propagated only the parental genotype, DTS/CyO. Because Drosophila have only three chromosomes of appreciable length, there are only three balancer chromosomes in common use.

What is an enhancer trap line?

Enhancer Trap. MGI Glossary. Definition. A type of DNA construct containing a reporter gene sequence downstream of a promoter that is capable of integrating into random chromosomal locations in mouse. Integration of the enhancer trap near an enhancer allows the expression of a new mRNA encoding the reporter gene.

Why are polytene chromosomes so large?

Structure. In insects, polytene chromosomes are commonly found in the salivary glands; they are also referred to as “salivary gland chromosomes”. The large size of the chromosome is due to the presence of many longitudinal strands called chromonemata; hence the name polytene (many stranded).

Why do men Mutagenize?

Usually you mutagenize males with EMS or X-rays. Males are used because they don’t need to be virgins. Also they are more resistant to DNA damage, which means they can tolerate enough damage to get useful mutations. Note that you only care about mutations in the germline, not soma.

How long does Drosophila melanogaster live?

Under optimal growth conditions at 25 °C (77 °F), the D. melanogaster lifespan is about 50 days from egg to death. The developmental period for D. melanogaster varies with temperature, as with many ectothermic species.

How does an enhancer trap work?

Glossary:Enhancer Trap. A type of DNA construct containing a reporter gene sequence downstream of a promoter that is capable of integrating into random chromosomal locations in mouse. Integration of the enhancer trap near an enhancer allows the expression of a new mRNA encoding the reporter gene.

How effective is the Ht1 (I) balancer?

Very effective balancer for left portion of LG I from the left end through let-80, and the left portion of LG V from the left end through dpy-11. hT1 (I) is LG V (left) translocated to LG I (right), disjoins from normal LG I. hT1 (V) is LG I (left) translocated to LG V (right), disjoins from normal LG V.

What is the best strain balancer for LG III?

Very effective balancer for right portion of LG III from right end through tra-1 and vab-7. Origin/Mutagen: Acetaldehyde mutagenesis. Recommended use: General balancing, strain maintenance. Reference strain: CB1517, eDf2 III; eDp6 (III;f). Phenotype: Unc-119. Segregants: Unc-119.

What is the use of balancer in genetic testing?

Balancers have been used in mutant screens most commonly for recovery of lethal mutations, but they can also be used to recover nonlethal mutations. For example, they can be used in noncomplementation screens for new alleles of existing morphological mutations.

When to use morphologically marked balancer variants?

Morphologically marked balancer variants are used when a homozygous viable balancer does not already have a unique phenotype, when its phenotype is similar to that of one of the progeny classes, or when a second scorable phenotype is needed in addition to the balancer’s native homozygous phenotype.