What is a balancer genetics?
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 balancer chromosomes in 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.
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 …
Why do we use balancer chromosomes?
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 many chromosomes are present in Drosophila?
4 chromosomes
While drosophila only have a total of 4 chromosomes, they too display sexual dimorphism, with females carrying the double X chromosomes and males carrying XY. The two X chromosomes in female fruit flies, as in mammals, make them a homozygous sex as compared with the XY condition in males, known as heterozygous.
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.
What do polytene chromosomes do?
Polytene chromosomes, at interphase, are seen to have distinct thick and thin banding patterns. These patterns were originally used to help map chromosomes, identify small chromosome mutations, and in taxonomic identification. They are now used to study the function of genes in transcription.
How do polytene chromosomes of an insect differ from normal chromosomes?
Secondly, at the end of each S-phase, DNA strands do not segregate; instead they remain paired to each other, forming polytene (“multi-stranded”) chromosomes. As a result, giant chromosomes is formed, and these giant chromosomes are 70–110 times longer than typical metaphase chromosomes (Fig.
What is the dominant gene for eye color?
BIOTECH Basics. Countless students have been taught that a single gene controls eye color, with the allele for brown eyes being dominant over blue. Scientists now realize such a model is overly simplistic and incorrect.
What is a genetic balancer in biology?
Introduction 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.
Are brown eyes dominant or recessive genes?
The brown-eyed offspring may have either a pair of dominant genes, or mixed genes. In this example, all of the children will have brown eyes. This is because each child receives a recessive gene from one parent and a dominant gene from the other parent.
What are some of the best articles on genetic balancers?
Abstract Article Genetic balancers 28 Brenner, S. (1974). The genetics of Caenorhabditis elegans. Genetics 77, 71–94. Abstract Bucher, E.A., and Greenwald, I. (1991). A genetic mosaic screen of essential zygotic genes in Caenorhabditis elegans. Genetics 128, 281–292. Abstract C. elegans Sequencing Consortium (1998).