Human VNTR Biology 101 October 23, 2009 Lab Partner: INTRODUCTION All human beings have genomes, or DNA that include all of their unique genetic information. Every strand of DNA is different per individual, which accounts for human diversity in the world. Variable Number Tandem Repeat (VNTR) is a short sequence of DNA that is repeated at a specific chromosomal locus. The number of tandem repeated units vary between individuals; therefore, every human being’s unique sequence of base pairs can be used for personal or parental identification (The Biology Project 1996).
In this experiment, we extracted DNA from our cheek cells to detect our individual VNTR. Our objective was to find out our approximate repeat numbers on Chromosome 1 and to see if we are homozygous or heterozygous. Homozygous is when one receives a different number of chromosomes from his or her mother and father, and homozygous is when one receives the same number of chromosomes from his or her mother and father. I expected that I would be heterozygous, since according to the lab manual, there is an 80% chance of having different numbers of repeats on both chromosomes, which is much higher than a 20% chance of being homozygous.
MATERIALS AND METHODS In this experiment, we extracted DNA from cheek cells, loaded PCR products in a 1% agarose gel and took gel images. When loading our mixtures into the wells on the gel, we worked with positive and negative controls. The negative controls consisted of water and the positive controls consisted of purchased human DNA. The last two tubes consisted of buccal DNA. Please see lab manual for specific details.
RESULTS My DNA band sizes were estimated from the standard DNA ladder lane, from which all the band sizes were known and the distances traveled for both the standard DNA ladder lane and my DNA bands were measured (Table 2).The standard curve helped estimate the corresponding base pairs DNA of my DNA bands from the distances traveled (Figure 1). My DNA VNTR showed I am heterozygous and I have 19 and 22 repeats. DISCUSSIONS In this experiment, my photo indicated that I am heterozygous, meaning I have a different number of chromosomes from my mother and father. My photo proves this since the wide fluorescent box indicating my DNA seems to be lined up with the 500bp band size and also has a band size of 450bp.
From these base pairs DNA, my results indicated I have 22 and 19 repeats. According to the allele frequency table (Table 1), allele 19 showed an equal percentage of . 5% in Caucasians and African Americans, and was not present in Hispanic Americans. The allele 22 showed a higher percentage in the African American race of 10. 8%, 3% in Caucasians and 2. 9% in Hispanic Americans.
The potential uses of VNTR in society have become essential to forensic crime investigations, using DNA fingerprinting and CODIS and for paternity testing.DNA fingerprinting is used to assist in the identification of individuals on the basis of their respective DNA profiles (Brinton and Lieberman 1994). CODIS (Combined DNA Index System) is a DNA database funded by the FBI consisting of DNA profiles from convicted offenders, unsolved crime scene evidence and missing people (DNA Initiative). In the process of paternity testing, DNA samples from two possible fathers, the mother, and the offspring’s DNA are each loaded into a well on the gel and ran through the gel electrophoresis (LeVay and Valente 2003).
These processes are incredibly accurate because there are millions of base pairs in each person’s DNA and every person has a different sequence. Therefore, every person can be identified solely by the sequence of his or her base pairs (Brinton and Lieberman 1994). ACKNOWLEDGEMENTS I would like to thank Professor Cramer and Professor Tome for helping me understand how to read my DNA VNTR photo and better understand the lab results. I would also like to thank my Writing Center tutor in organizing my report and my lab partner for answering questions I was unsure of.LITERATURE CITED Brinton, Kate, and Kim-An Lieberman.
"VNTRs. " Basics of DNA Fingerprinting. May 1994. Web.
19 Oct 2009. <http://protist. biology. washington. edu/fingerprint/dnaintro. html>.
"VNTR: Hypervariable regions. " The Biology Project. 1996. The Biology Project, Web. 21 Oct 2009.
<http://www. biology. arizona. edu>. LeVay, and Valente.
"Paternity Testing. " Human Sexuality. 2003. Sinauer Associates, Web. 21 Oct 2009.
<http://www. sumanasinc. com>. Advancing Criminal Justice Through DNA Technology. " DNA Initiative.
USA. gov, Web. 21 Oct 2009. <http://www. dna.
gov/solving- crimes/cold-cases/howdatabasesaid/codis/>. Table 2. This table shows the distances traveled in millimeters and the corresponding base pairs DNA of our standard DNA ladder lane and my DNA bands. | Distance Traveled (mm)| Base Pairs DNA| Standard DNA ladder lane| 21| 2000| | 27| 1000| | 34| 500| | 39| 250| | 42| 100| | | | My DNA bands| 33| 500| | 34| 450|
