Embed Size (px)
Citation preview
DNA fingerprinting is a technology that identifies particular individuals using properties of their DNA It is also termed DNA profiling
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
19.4 DNA FINGERPRINTING
19-62
When subjected to DNA fingerprinting, chromosomal DNA gives rise to a series of bands on a gel The order of bands is an individual’s DNA
fingerprint It is the unique pattern of these bands that makes it
possible to distinguish individuals
Certain loci in human chromosomes are variable in length These loci contain tandemly repeated sequences
called minisatellites Variable Number of Tandem Repeats (VNTRs)
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 19-63
19-64Figure 19.17
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
VNTRsRestriction enzyme sites
DNA probes are used to hybridize
specifically to the repeat sequence
located within VNTRs
Figure 19.18 Protocol for DNA fingerprinting
19-65
19-66
Figure 19.18 Protocol for DNA fingerprinting
The probe is called a multilocus probe (MLS)
It binds to ~ 20 to 40 fragments of DNA that contain the sequence
Mixed probesA+B
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
DNA fingerprints from a murder case
Defendant’sblood (D)
Blood fromdefendant’sclothes
Victim’sblood (V)
D Jeans shirt V
4 g 8 g
RFLPs as markers for disease-causing alleles
RFLP markerDNA
Disease-causingallele
Normal allele
In the past decade, the technique of DNA fingerprinting has become automated It is now done using PCR, which amplifies short tandem
repeat sequences (STRs) Like VNTRs, STRs are found in multiple sites in human
genomes and are variable among different individuals The main difference between a VNTR and STR is size
STRs are much shorter, usually 100–450 bp STRs are called microsatellites, and VNTRs minisatellites
The amplified STRs are fluorescently labeled They are separated by gel electrophoresis A laser excites the fluorescent molecule within the STR A detector records the amount of emission for each STR
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 19-67
19-68
Figure 19.18 Protocol for DNA fingerprinting
Each peak has a characteristic mass
The pattern of peaks is an individual’s DNA fingerprint
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Within the past decade, the uses of DNA fingerprinting have expanded in many ways In medicine, it is used identify different species of bacteria
and fungi and also different strains of the same species This is useful for appropriate antibiotic treatment
DNA fingerprinting is also used in forensics and relationship testing
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Uses of DNA Fingerprinting
19-69
19-71
Figure 19.19 The use of DNA fingerprinting to establish paternity
Male 2 does not have many of the child’s
paternal bands
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Therefore he cannot be the biological father
Male 1 has all the child’s paternal bands
The probability of this occurring by chance alone
is very small
Therefore he is the biological father
