Group items tagged

Polymerase Chain Reaction (PCR) Analysis PCR analysis is a technique that allows technicians to create millions of precise DNA replications from a single sample of DNA. In fact, DNA amplification alongside PCR can let forensic scientists perform DNA analysis on samples that are as tiny as only a couple of skin cells. In contrast to some other DNA analysis techniques, PCR analysis has the advantage of analysing minuscule sample sizes, even if they are degraded although they must not be contaminated with DNA from other sources during the collection, storage and transport of the sample.

RFLP is a technique for analyzing the variable lengths of DNA fragments that result from digesting a DNA sample with a special kind of enzyme. This enzyme, a restriction endonuclease, cuts DNA at a specific sequence pattern know as a restriction endonuclease recognition site. The presence or absence of certain recognition sites in a DNA sample generates variable lengths of DNA fragments, which are separated using gel electrophoresis. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample. RFLP was one of the first applications of DNA analysis to forensic investigation. With the development of newer, more efficient DNA-analysis techniques, RFLP is not used as much as it once was because it requires relatively large amounts of DNA. In addition, samples degraded by environmental factors, such as dirt or mold, do not work well with RFLP.

PCR Analysis Polymerase chain reaction (PCR) is used to make millions of exact copies of DNA from a biological sample. DNA amplification with PCR allows DNA analysis on biological samples as small as a few skin cells. With RFLP, DNA samples would have to be about the size of a quarter. The ability of PCR to amplify such tiny quantities of DNA enables even highly degraded samples to be analyzed. Great care, however, must be taken to prevent contamination with other biological materials during the identifying, collecting, and preserving of a sample.

Short tandem repeat (STR) technology is used to evaluate specific regions (loci) within nuclear DNA. Variability in STR regions can be used to distinguish one DNA profile from another. The Federal Bureau of Investigation (FBI) uses a standard set of 13 specific STR regions for CODIS. CODIS is a software program that operates local, state, and national databases of DNA profiles from convicted offenders, unsolved crime scene evidence, and missing persons. The odds that two individuals will have the same 13-loci DNA profile is about one in a billion.

In 2012, readers searching for forensic science content now have many more ways to find

relevant material.  Organized blogs devoted to forensic science have appeared that post both links and original content.  Organizations have twitter accounts and Facebook pages that make reaching readers much easier than in RSS days.

Investigators have found new DNA evidence in the murder of Peggy Hettrick, a case that was considered closed until genetic evidence freed a man who spent 10 years in prison, according to Colorado Attorney General John Suthers.The "touch DNA" tests weren't available in the late 1990s. Timothy Masters was convicted of murder in Hettrick's death in 1999, but his conviction was overturned in 2008 after defense lawyers used advanced DNA testing to uncover evidence suggesting a different suspect.The new evidence was taken from Hettrick's clothing. "We have done 'touch DNA,' and I think it has moved the ball forward. We will know more in the future," Suthers said. He wouldn't say whose DNA was found or identify the clothing on which it was found.Masters has not been exonerated in the case and remains a suspect."While we are not in a position to exonerate Tim at this time, I emphasize that he is presumed innocent and is no more a suspect than a variety of other people," Suthers said.

The first technique of genetic engineering, the plasmid method, is the most familiar technique of the three, and is generally used for altering microorganisms such as bacteria. In the plasmid method, a small ring of DNA called a plasmid (generally found in bacteria) is placed in a container with special restriction enzymes that cut the DNA at a certain recognizable sequence. The same enzyme is then used to treat the DNA sequence to be engineered into the bacteria; this procedure creates "sticky ends" that will fuse together if given the opportunity. Next, the two separate cut-up DNA sequences are introduced into the same container, where the sticky ends allow them to fuse, thus forming a ring of DNA with additional content. new enzymes are added to help cement the new linkages, and the culture is then separated by molecular weight. Those molecules that weigh the most have successfully incorporated the new DNA, and they are to be preserved. The next step involves adding the newly formed plasmids to a culture of live bacteria with known genomes, some of which will take up the free-floating plasmids and begin to express them. In general, the DNA introduced into the plasmid will include not only instructions for making a protein, but also antibiotic-resistance genes. These resistance genes can then be used to separate the bacteria which have taken up the plasmid from those that have not. The scientist simply adds the appropriate antibiotic, and the survivors are virtually guaranteed (barring spontaneous mutations) to possess the new genes.

Next, the scientist allows the successfully altered bacteria to grow and reproduce. They can now be used in experiments or put to work in industry. Furthermore, the bacteria can be allowed to evolve on their own, with a "selection pressure" provided by the scientist for producing more protein. Because of the power of natural selection, the bacteria produced after many generations will outperform the best of the early generations. Many people strongly object to the plasmid method of genetic engineering because they fear that the engineered plasmids will be transferred into other bacteria which would cause problems if they expressed the gene. Lateral gene transfer of this type is indeed quite common in bacteria, but in general the bacteria engineered by this method do not come in contact with natural bacteria except in controlled laboratory conditions. Those bacteria that will be used in the wild - for example, those that could clean up oil spills - are generally released for a specific purpose and in a specific area, and they are carefully supervised by scientists.

Using a newly applied scientific technique, researchers at the Keck School of Medicine of USC have reached surprising findings about the role of nature versus nurture in the development of the neural circuits in the auditory cortex, the area of the brain responsible for processing information about sound.

Fusion cell cloning

Fusion cell cloning involves replacing the nucleus of an unfertilised egg with the nucleus from a different cell.

The classical twin study design relies on studying twins raised in the same family environments. Monozygotic (identical) twins share all of their genes, while dizygotic (fraternal) twins share only about 50 percent of them. So, if a researcher compares the similarity between sets of identical twins to the similarity between sets of fraternal twins for a particular trait, then any excess likeness between the identical twins should be due to genes rather than environment.Researchers use this method, and variations on it, to estimate the heritability of traits: The percentage of variance in a population due to genes. Modern twin studies also try to quantify the effect of a person's shared environment (family) and unique environment (the individual events that shape a life) on a trait.The assumptions those studies rest on--questioned by some psychologists, including, in recent work, Jaccard--include:

What is a Clone

In biology, a clone is a cell or an organism that is genetically identical to another cell or organism.

How was Dolly Created? Dolly is different. She was generated from a specialized adult cell, not from an unspecialized embryonic cell.

Recent advances in forensic DNA testing are now paving the way for reforming the manner by which cases are resolved in courts of law through the way suspected offenders are apprehended during a criminal investigation. Firstly, the availability of new markers which are more variable across different populations, adds to the increased power of discrimination once more genetic markers are used. From the time when DNA testing only involved seven to nine genetic markers to evaluate if crime scene evidence matches a suspect’s profile, as well as to determine relationships, to the current battery of 21 autosomal markers and 23 male-specific markers, the capacity of DNA profiling to differentiate individuals has increased significantly. The use of automated and expert systems for large-scale analysis has also been found to reduce manual errors and to increase output per unit time. The use of several dyes in a single multiplex system provides more information from the same amount of genetic material compared to reactions targeting only one genetic marker but requiring the same amount of DNA that was common in the early 1990s.