Chapter 12: Forensic DNA Profiling

Karl Landsteiner

The foundations of forensic genetics were laid down when ________ described ABO blood group systems in 1901.

post mortem

In ________ cases DNA can be obtained from body tissues.

probability of discrimination

The frequencies of the markers are important as these are to be used in calculating the ________ and /or match by multiplying them together.

genetic characteristics

It defines that individuals ________ contains a large number of polymorphisms that can be used for human identification.

DNA methods

________ avoid any complications of dominance or recessives.

Genotype of the Person

allelic configuration at a locus

Profile of the Person

genotypes at different loci

Variable number of tandem repeats (VNTRs)

minisatellite polymorphisms in a large number of tandemly repeating units of a particular sequence typically 16-80 bp long

Polymerase Chain Reaction (PCR)

an in vitro molecular photocopying process that generates millions of copies of the target DNA sequence the boundaries of which are defined by synthetic oligonucleotide primers that are complementary to the 3' ends of the sequence

Denaturation of DNA

The two strands of DNA are wrapped around each other, for replication the DNA has to unwind to have a single strand available for the synthesis of the new strand

AmpFLPs

smaller minisatellite loci which had alleles from 9-15 bp, composed of short core repeat units**

Short Tandem Repeats (STRs)

microsatellites that are an abundant class of DNA polymorphisms

Multiplex PCR

this is where each primer pair would amplify a specific sequence or STR

Multiplexing

a technique where a number of STR loci are amplified in a single tube PCR

Allelic ladder

consists of a number of alleles of a STR system and is used as a reference to designate the alleles

Genotyper

the programme would call the allele on the basis of the established windows, which is called the ‘absolute window method

DYS19

described as the first STR on the human Y-chromosome, which was found to be polymorphic and suitable for sex and paternity determination in deficiency cases

Match Probability

the probability that the two randomly selected individuals will have identical genotype

Power of Discrimination

the probability that two randomly selected individuals will have different genotypes

Karl Landsteiner

He introduced the ABO blood group systems.

Sir Alec Jeffrey

He introduced VNTRs

Complex repeats

consider two alleles of locus D21S11

DNA

the biological blueprint of life.

deoxyribonucleic acid (DNA)

The structure of ______ was described by *James Watson* and *Francis Crick* in 1953.

right-handed double

DNA was determined to be a ________ helix.

nucleotides

DNA’s repeating subunits

Nuclear DNA

is inherited equally from both mother and father.

Mitochondrial DNA

is inherited only from the mother, and therefore it can be used to match with the maternal lineages.

**chromosomes**

* There are 3 billion base pairs (bp) in a single copy of the human genome.
* These are arranged in compact structures, which we all know as **_______**.

diploid cells

There are 23 pairs of chromosomes in all the cells of humans and so are called ______.

haploid cells

Only in the gametes, one copy of each chromosome is present and these are called _______.

coding and non-coding

The DNA in the chromosomes is arranged as ______ regions.

Introns

functional portions of the genes.

Exons

non-functional regions of the genes.

Loci

polymorphic markers have been detected in the areas of the human genomes.

Alleles

an alternative form of the marker at a particular locus.

Homozygote

it is if the alleles are the same.

Heterozygote

it is if the alleles are different.

Genotype of the Person

allelic configuration at a locus.

Profile of the Person

genotypes at different loci.

tandemly repetitive DNA

Segments of DNA are arranged as a particular sequence being repeated more than once, a sequence GGGCCCTTAA might be repeated many times

Variable number of tandem repeats (VNTRs)

minisatellite polymorphisms in many tandemly repeating units of a particular sequence, typically 16-80 bp long.

Polymerase Chain Reaction (PCR)

an invitro-molecular photocopying process that generates millions of copies of the target DNA sequence, the boundaries of which are defined by synthetic oligonucleotide primers that are complementary to the 3' ends of the sequence.

Denaturation of DNA

The two strands of DNA are wrapped around each other, for replication the DNA has to unwind to have a single strand available for the synthesis of the new strand.

AmpFLPs

A smaller minisatellite loci that had alleles from 9-15 bp, composed of short core repeat units.

Short Tandem Repeats (STRs)

microsatellites that are an abundant class of DNA polymorphisms.

DNA analysis

STRs form the basis of forensic _____.

Multiplex PCR

this is where each primer pair would amplify a specific sequence or STR.

Forensic Science Services (FSS)

The first multiplex PCR kit was developed by the _______ of the UK and it comprised four STR loci, THO1, vWA, FES/FPS, and F13A1.

second generation multiplex (SGM)

The FSS then launched its ________ comprising of six STR loci THO1, FGA, D8S1179, D18S51 and D21S11.

Simple consisting of 1 repeating sequence

an STR locus has several alleles but each allele differs only in several repeats but the sequence of the repeats is the same.

Simple with non-consensus alleles

consider two alleles of locus HUMTHO1.

Compound with non-consensus alleles

considers two alleles of the locus vWA.

Complex repeats

consider two alleles of locus D21S11

Hypervariable repeats

SE33. Few loci have not only different repeat regions; they also have them arranged in many different ways.

slipped strand mispairing

Sometimes, ‘________’ leads to a mutation in regions of the genome, having abundant simple repetitive sequences which have been recognized as the major mechanism involved in their generation.

ABI GeneScan®

The automated systems such as ________ allowed electrophoretic information to be stored and tabulated as the alleles migrated through a gel matrix and pass a laser detection window.

Multiplexing

a technique where several STR loci are amplified in a single tube PCR.

Allelic ladder

consists of several alleles of an STR system and is used as a reference to designate the alleles.

Genotyper

the program would call the allele based on the established windows, which is called the ‘absolute window method’.

Maternity identification

is necessary to identify the mother in cases of child abandonment or infanticide or swapping of neonates.

Paternity identification

is important in cases of sexual assault in which pregnancy occurs and pregnancy is either terminated or goes to full term.

AMPFLSTR® SGM Plus

The FSS has started profiling criminal cases using the 11 loci _______kit.

DYS19

Described as the first STR on the human Y-chromosome, which was found to be polymorphic and suitable for sex and paternity determination in deficiency cases.

Y STR analysis

____ can be valuable in mixture interpretation in multiple rape cases or the detection of male specific profile in azoospermia/vasectomized male suspects when spermatozoa are not available.

multiplex systems

The ______ are mostly used as both are robust and reproducible and, together, allow seven Y STRs to be analyzed. These systems are therefore favored at the moment.

Y-PLEXTM 6

A new multiplex capable of amplifying seven Y STR loci, the ‘______’ has been recently developed by a commercial firm Reliagene, Technologies, Inc. USA.

Match Probability Formula

Power of Discrimination Formula

Match Probability

the probability that the two randomly selected individuals will have identical genotypes.

Power of Discrimination

the probability that two randomly selected individuals will have different genotypes. This is the reciprocal of the probability of a match.