Transcription in Eukaryotes
DNA replication is more complex in eukaryotes in large part because there is a lot more DNA to copy. Transcription is more complicated in eukaryotes for following reasons. The larger eukaryotic genomes have many more genes to be recognized and transcribed. Whereas bacteria usually have a few thousand genes, eukaryotes have tens of thousands of […]
Transcription
The process of formation of RNA from DNA template. The first step of information transfer from gene to protein is to produce an RNA strand whose base sequence matches the base sequence of a DNA segment, sometimes followed by modification of that RNA to prepare it for its specific cellular roles. Hence RNA is produced […]
Mechanism of DNA Replication
The process of doubling of DNA is called replication DNA REPLICATION IN PROKARYOTES Origin site: Replication starts at a single origin in the circular bacterial chromosome. The double helix opens up and both strands serve as template for the synthesis of new DNA. Gyrase: it is a type of topoisomerases and responsible for removing […]
Three-point testcross
is a cross of a trihybrid (triple heterozygote) to a triply recessive tester. This kind of cross, called a three-point testcross, is a commonly used format in linkage analysis. The goal is to deduce whether the three genes are linked and, if they are, to deduce their order and the map distances between them. Example […]
Recombination of linked genes is by crossing-over
In Morgan’s study, the linked genes could not assort independently, but there were still some recombinants, which as we have seen, must have been produced by crossovers. In general, for genes close together on the same chromosome pair, recombinant frequencies are significantly lower than 50 percent
Recombination of unlinked genes is by independent assortment
In a dihybrid with genes on separate chromosomes,recombinants are produced by independent assortment,as shown in Figure 1. Let’s reconstruct a standard Mendelian analysis to illustrate how recombinants are produced: P A/A ; B/B x a/a ; b/b Gametes A ; B […]
Genetic Recombination
The production of new allele combinations is formally called recombination. Crossovers are one mechanism for recombination, and so is independent assortment. Recombination is observed in a variety of biological situations, but for the present let’s define it in relation to meiosis. Meiotic recombination is defined as any meiotic process that generates a haploid product with […]
Multiple Crossovers can involve more than two chromatids
Tetrad analysis can also show two other important features of crossing-over. First, in one meiocyte several crossovers can occur along a chromosome pair. Second, in any one meiocyte these multiple crossovers can involve more than two chromatids. To think about this issue, we need to look at the simplest case: double crossovers. To study double […]
Linkage
The genes which reside on the same chromosome are said to be linked, and this phenomenon is called linkage. Linkage groups: All those genes which are located on the same chromosomes constitute a linkage group. For example, there are four (4) linkage groups in Drosophila melanogaster, 7 in Pisum sativum and 23 in man. Each […]
Tissue Culture Importance
Plant tissue culture is one of the most rapidly growing areas of biotechnology because of its high potential to develop improved crops and ornamental plants. With the advances made in the tissue culture technology, it is now possible to regenerate species of any plant in the laboratory. Application in Research Work: Tissue culture techniques […]