dna fingerprinting (dna 指紋圖譜 ) by yu zhi heng 7b (30)
TRANSCRIPT
DNA fingerprinting
(DNA 指紋圖譜 )
By Yu Zhi Heng
7B (30)
Historical background DNA fingerprinting was developed in 1984 by Alec. J. Jeffrey at the University of Leic
ester He was studying the gene of myoglobin.
This is a picture of Alec. J. Jeffrey
What is DNA Fingerprinting? The chemical structure of everyone's DNA is the
same. The only difference between people (or any
animal) is the order of the base pairs. The information contained in DNA is determined
primarily by the sequence of letters along the zipper.
Structure of DNA
The different sequence segments that vary in size and composition and have no apparent function are called minisatellites
The different sequences is the same as the word "POST" has a different meaning from "STOP" or "POTS," even though they use the same letters. i
Using these sequences, every person could be identified solely by the sequence of their base pairs
there are so many millions of base pairs, the task would be very time-consuming
Instead, scientists are able to use a shorter method, because of repeating patterns in DNA.
These patterns do not, however, give an individual "fingerprint,"
they are able to determine whether two DNA samples are from the same person, related people, or non-related people.
DNA Fingerprinting using VNTR's On some human chromosomes, a short sequence of
DNA has been repeated a number of times. the repeat number may vary from one to thirty repe
ats these repeat regions are usually bounded by specific
restriction enzyme sites cut out the segment of the chromosome containing t
his variable number of tandem repeats (VNTR's ) identify the VNTR's for the DNA sequence of the re
peat.
Making DNA Fingerprints
DNA fingerprinting is a laboratory procedure that requires six steps:
1: Isolation of DNA.
2: Cutting, sizing, and sorting. Special enzymes called restriction enzymes
are used to cut the DNA at specific places
3: Transfer of DNA to nylon.The distribution of DNA pieces
is transferred to a nylon sheet by placing the sheet on the gel and soaking them overnight.
4-5: Probing.Adding radioactive or colored probes to the nylon sheet produces a pattern called the DNA fingerprint.
4-6: DNA fingerprint. The final DNA fingerprint is built by using se
veral probes (5-10 or more) simultaneously.
Practical Applications of DNA Fingerprinting 1.Paternity and Maternity person inherits his or her VNTRs from his
or her parents Parent-child VNTR pattern analysis has be
en used to solve standard father-identification cases Can someone tell me who is my father?
2. Criminal Identification and Forensics DNA isolated from blood, hair, skin cells, or
other genetic evidence left at the scene of a crime can be compared
FBI and police labs around the U.S. have begun to use DNA fingerprints to link suspects to biological evidence – blood or semen stains, hair, or items of clothing
3. Personal Identification The notion of using DNA fingerprints as a sort of
genetic bar code to identify individuals has been discussed
4.Diagnosis of Inherited Disorders diagnose inherited disorders in both prenatal and
newborn babies These disorders may include cystic fibrosis, hemo
philia, Huntington's disease, familial Alzheimer's, sickle cell anemia, thalassemia, and many others.
5.Developing Cures for Inherited Disorders By studying the DNA fingerprints of relatives wh
o have a history of some particular disorder identify DNA patterns associated with the disease 6.identification of Chinese medicine The Hong Kong Baptist University was able to us
e DNA fingerprinting to identify the Chinese medicine—Lingzhi in 2000
Considerations when evaluating DNA evidence In the early days of the use of
genetic fingerprinting as criminal
evidence, given a match that had a
1 in 5 million probability of occurring
by chance the lawyer would argue
that this meant that in a country
of say 60 million people there were 12 people
who would also match the profile.
2. Problems with Determining Probability A. Population Genetics VNTRs, because they are results of genetic
inheritance it will vary depending on an individual's ge
netic background
B. Technical Difficulties Errors in the hybridization and probing process
must also be figured into the probability Until recently, the standards for determining
DNA fingerprinting matches, and for laboratory security and accuracy which would minimize error
When evaluating a DNA match, the following questions should be asked:
-Could it be an accidental random match?
-If not, could the DNA sample have been planted?
-If not, did the accused leave the DNA sample at the exact time of the crime?
-If yes, does that mean that the accused is guilty of the crime?
A Kid’s set of apparatus for DNA fingerprinting, What does it mean?
END