Answer:
Transmission electron microscope (MET): allows sample observation in ultra-thin sections. A TEM directs the electron beam towards the object to be increased. A part of the electrons bounce or are absorbed by the object and others pass through it forming an enlarged image of the specimen. To use a TEM, the sample must be cut into thin layers, not larger than a couple thousand thousands of angstroms. A photographic plate or a fluorescent screen is placed behind the object to record the enlarged image. Transmission electron microscopes can increase an object up to a million times.
A scanning electron microscope creates an enlarged image of the surface of an object. It is not necessary to cut the object into layers to observe it with an SEM, but it can be placed in the microscope with very few preparations. The SEM scans the image surface point by point, unlike the TEM, which examines a large part of the sample each time. Its operation is based on traversing the sample with a very concentrated beam of electrons, similar to the scanning of an electron beam on a television screen. The electrons in the beam can disperse from the sample or cause secondary electrons to appear. Lost and secondary electrons are collected and counted by an electronic device located on the sides of the specimen. Each point read from the sample corresponds to a pixel on a television monitor. The higher the number of electrons counted by the device, the greater the brightness of the pixel on the screen. As the electron beam sweeps the sample, the entire image of it is presented on the monitor. Scanning electron microscopes can enlarge objects 200,000 times or more. This type of microscope is very useful because, unlike TEM or optical microscopes, it produces realistic three-dimensional images of the object's surface.
The evaluation of their DNA and short tandem repeats will let them know if the birds are related or not. The genetic linkage will provide information about their common ancestry as well as if they belong to the same species, or are closely related species.
<span>it was molecular structure of DNA this was appeared 1n April 1953 Watson and Crick presented the structure of DNA- Helix.it carried the genetic information. the DNA Molecule shaped in twisted ladder.franklin produced an X- ray photograph.
DNA structure is made of molecules called nucleotide. Watson and crick also work on 3-D structure of DNA. this mark the history in molecular biology to understanding the genes control and genetic information.they also work on cell.they use stick and ball to understand to test their idea.</span>
