DNA Testing: The Linkage Test

There are 3 major ways to test the DNA. The question is which one of those are going to the best for genetic disorders and why?

The answer to the question is that the microscope and biochemical tests are of not really useful for detecting most of the genetic disorders because many of these genetic disorders are the result from defects on a single gene.

This leaves us with only one approach, the linkage test. This DNA talent test will enable us to predict if there is a single mutated gene. This test will let us know about what happened to these genes and what changes have occurred in its DNA sequence, even what function this gene does in the cells. Linkage tests can often be used in situations in which a direct DNA test cannot be done.

How does the linkage test work?

This test will look for a known region of the DNA located close to the target gene to be used as a marker if there is no way to detect this target gene.

Then by following the marker, predictions can be made about the state of the target gene. The marker serves as an indicator.

Linkage testing also relies on two regions of DNA that are close each other. The closer these two DNA regions are to each other on the chromosome, the more likely it is they will stay together and be inherited together. If they are not very close, then they can occasionally become separated from each other by the processes of chromosome breakage and exchange of pieces which occurs between members of the same chromosomic.

There are several types of DNA markers are useful for linkage testing:

  • One type of marker can simply be another gene which is located very close to the target gene that can be measured. Keeping track of the marker gene provides important information about whether or not the mutant gene has been inherited. If we can find a strong indication that the marker gene has been passed along from a parent to a child, it proves that the nearby mutant gene has also been inherited. On the other hand, the absence of the marker gene is a strong indication that the mutant gene is also absent.

Another useful marker that takes advantage of differences in base sequences of the DNA molecule in the vicinity of the target gene. These small variations in the base sequence occur at many places scattered throughout the DNA. By some estimates, a single base-pair variation along the DNA molecule occurs about once every five hundred base pairs. This means that the DNA sequence found on one chromosome can and does differ slightly from the DNA sequence of its partner chromosome. The DNA molecules of the partner chromosomes can also differ from each other in another way: Some places on the chromosomes can contain extended sequences where one type of base alternates with other many times. These variations are generally without any harmful effects and go unnoticed by the organism since the vast majority of them occur in those extensive “junk” DNA portions of the chromosomes.

Leave a Reply

Your email address will not be published. Required fields are marked *