Answers to lab manual for dna fingerprinting lab 103

Electrophoresis is used to study the lengths of DNA and how they compare against different strands. RFLP stands for restriction fragment length polymorphism, which is the variation of lengths presented in a gel electrophoresis procedure. Restriction enzymes cut DNA in specific places. If a DNA strand has more restriction enzymes, then the DNA strands will be cut into smaller pieces and will move further to the positive side on a gel electrophoresis test.

Ligase forms a chemical bonds that joins two molecules together. Works Cited. Gel Electrophoresis. Retrieved February 01, Principles of Gel Electrophoresis. Biology Animation Library. Retrieved February 1, LabBench Activity.

Smithies, O. How it all began: A personal history of gel electrophoresis. Biology Lab Notebook. Search this site. Chick Development Lab. Coli Transformation Lab. Fermentation Lab. Lab 5 - Mitosis. Lab 7 - Gel Electrophoresis. Lab Report 1 - Osmosis. Schematic representation of a hypothetical case of paternity dispute showing the STR vWA locus typing result of the alleged father, the child and the mother with allelic ladders run adjacent to the test samples.

Note that the allelic number assignment commences from the bottom and ascends by one unit increment to the top. Reading of the profile is easy and unambiguous - Alleged Father — [13,15]; Child — [14,15]; Mother — [14,14]. The alleged father cannot be ruled out as the biological father.

Alec J. Tests proved that the suspect had not committed the crimes. Two other important early cases gave much impetus to the use of DNA evidence: They were, the case of Glen Dale Woodal versus the State of West Virginia in and the multiple murder trial of Timothy Wilson Spencer versus the state of Virginia in The DNA evidence in the Woodal case exonerated him while that of the Spencer case resulted in his conviction and sentencing to the death penalty.

Jose Castro was accused of murdering one Vimla Pence and her two year old daughter. He was convicted after admitting to the crime. In this case, the DNA tests conducted by Life Code Corporation did not include a specific test for human blood and also did not include blind testing protocols in the attempt to link the stain to the victims.

Furthermore, the laboratory in the above case had used contaminated probes and did not provide the worksheets and other manuscripts relating to the testing. Hence the court issued many directive guidelines regarding the test procedures and maintenance of laboratory results and reports as well as explanations for probability calculations and recording of observed defects or laboratory errors.

The need to identify and document chain of custody and allowing access to data, methodology and actual results for an independent expert to review were also instructed. In another case in , the Supreme Court of Minnesota had also refused to admit the DNA evidence analyzed by a private forensic laboratory. The court noted that the laboratory did not comply with appropriate standards and controls. In particular the court castigated the laboratory for failure to reveal its underlying population data and testing methods.

Such secrecy precluded replication of the test. Thus, courts have denounced improper application of DNA scientific techniques to particular cases, especially when used to declare matches based on frequency estimates.

However, DNA testing when properly applied is generally accepted as admissible and currently in many countries, DNA evidence is routinely used as evidence. In order to determine the probability that a particular genotype might occur at random in a population, population data must be compiled to make an estimate of the frequency of each possible allele and genotype.

Population databases are compiled based on ethnic or racial groups. Population subdivisions are not taken into account in the distribution of alleles. This can be illustrated by the following example.

Let us assume the DNA profile is based on six separate loci or genes, and that the suspect possesses alleles or versions of these that are present respectively in 8 percent, 1 percent, 5 percent, 10 percent, 10 percent and 2 percent of the total population. Then the chance that a random member of the population would have all 6 of these particular alleles is 0. The above calculation is valid when there are no associations among the alleles and they are distributed randomly throughout the population.

In fact, there are many population subgroups in an ethnic group. A few geneticists proposed that the frequencies of genetic markers could differ widely from the frequencies estimated in larger groups. Hence any estimate calculated may vary considerably. Another group of geneticists advocated that although population sub-groups exist, the method currently in use then, were so conservative that they can compensate for small sub-group variations.

In addition, the NRC report endorsed the use of DNA in courts, insisted for standardization proficiency tests and accreditation. The major reason for this reluctance was the advent of a new DNA typing method namely, STR typing , which obviated the need for most of the recommendations proposed in the first NRC report. Hence a second NRC committee was convened in The report categorically stated that the technology for DNA and the methods used for estimation of gene frequencies and related statistics should not be doubted if properly collected.

The NRC report addressed the issue of uniqueness of DNA typing and it stated that uniqueness excluding identical twins cannot be determined unless all members of the population are typed. The report further advocated that however, if a large number of loci are typed, the DNA profile obtained from the evidence can be so rare that it is highly likely that a suspect with a matching profile is the source of that evidence. The report further stated that to ensure a high degree of confidence regarding the source of DNA, a threshold probability value p should be established.

On this proposed suggestion an approach was developed at the FBI to determine a threshold value for examinations of DNA profile. The approach in brief is as follows:. An individual excluding identical twins can be identified as the source of the evidence DNA profile with a reasonable degree of certainty if the DNA profile satisfies the condition:.

In one Mrs. Debbie Smith was abducted from her home and was raped in the woods behind her house. Police arrested a suspect and conventional serological tests excluded the suspect. However physical evidences from the victim were preserved.

In many sexual assaults and rapes were reported in the vicinity where Debbie Smith lived. Police arrested a suspect and used DNA technology to investigate the crime. The suspect was however excluded. However the Police began to routinely preserve and document DNA profiles of unsolved cases and compiled DNA databases of criminals involved in violent crimes. Police had periodically searched the DNA profiles in the unsolved cases with the convicted offenders profiles.

The criminal, Norman Jimmerman, was already in prison for abduction and robbery and he is currently serving a year sentence. The current version of CODIS uses two indices to generate investigative leads in crimes where biological evidence is recovered from the crime scene.

The Convicted Offender index contains DNA profiles of individuals convicted of violent crimes, including sex offences. CODIS does not store criminal history information, case-related information, social security numbers or dates-of-birth.

Matches made among profiles in the Forensic Index can link crime scenes together; possibly identifying serial offenders. Based on a match, police can coordinate separate investigations, and share leads developed independently.

Matches made between the Forensic and Convicted Offender indices ultimately provide investigators with the identity of the suspect s. The Population File is a database of anonymous DNA profiles used to determine the statistical significance of a match.

CODIS is designed so that forensic laboratories have control over their own data. The system has three tiers or levels : local, state, and national. The Forensic and Convicted Offender indices, and the population file may exist at each tier. After sizing, examiners transfer unknown subject profiles into the local Forensic Index, where they are searched against other unknown subject profiles.

The custodian of the local database can share this data with other CODIS laboratories within the state by forwarding it to the state level. Over figures, more than 20 new to this edition, enhance student learning and understanding through visualization.

Experiments emphasize the scientific method —Enables students to put the scientific method into action while conducting experiments. Pre-lab assignments require students to demonstrate their understanding of background information by labeling illustrations and completing a portion of the laboratory report before delving into an actual laboratory technique.

A comprehensive Instructor's Manual contains a list of resources for materials, provides operational suggestions, and includes answer keys for quickly grading the lab reports. New to This Edition. Oil-Immersion Technique Appendix D. Classification of Organisms. Previous editions. Explorations in Basic Biology, 10th Edition. Sign In We're sorry!

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