Forensic Biology Exam – STR DNA
Markers, CODIS & Capillary
Electrophoresis (Lectures 7–
8)Complete Verified Questions
Provided with A+ Graded
Rationales Latest Updated 2026
STR sequences account for __% of the total human genome
3
More than _______ tetranucleotide STR loci have been characterized in the human genome.
20,000
Why are satellite markers not typically used in forensics?
Large regions, surround the centromere, not easy to amplify with PCR
Why are minisatellite (VNTR) markers not typically used in forensics?
Not good for degraded DNA, if very large diff in size amplification with PCR would favor the
smaller strand
Why are microsatellite (STR) markers typically used in forensics?
occur frequently, highly variable, no differential amplification during PCR
Why are STR dinucleotide repeats not preferable units?
Too simple, can cause stutters during PCR
Simple repeat STR marker category
contain units of identical length and sequence
Simple repeats with non-consensus alleles STR marker category
contain incomplete repeat units (e.g. allele 9.3)
Compound repeat STR marker category
, contain two or more adjacent simple repeats
Complex repeat STR marker category
may contain several repeat blocks of variable unit length as well as variable intervening
sequences
What is a DNA profile?
a specific DNA pattern obtained from a person/sample of body tissue
What is another name for non-consensus alleles (incomplete repeat units)?
microvariants
T/F: Microvariants can often be confused with split peaks.
True
How many of the original 13 core loci overlap between US and Europe?
8
Combined DNA Index System (CODIS)
general term for the FBI's DNA database and the program used to run the databases
Nationa DNA Index System (NDIS)
part of CODIS maintained at the national level which contains DNA profiles contributed by
federal, state, and local labs
Why are 3 reasons to expand the CODIS core loci from 13 to 20?
1. reduce adventitious matches
2. inc. international compatibility
3. inc. discrimination power
How does Amelogenin determine sex?
X-chromosome contains 6 bp deletion, resulting in a 106 bp product whereas a Y-chromosome
contains a 112 bp product
What are the 4 components of the Pre-PCR portion of a STR Typing Kit?
1. Primer mix
2. PCR rxn buffer and dNTPs
3. DNA polymerase
4. control DNA
Markers, CODIS & Capillary
Electrophoresis (Lectures 7–
8)Complete Verified Questions
Provided with A+ Graded
Rationales Latest Updated 2026
STR sequences account for __% of the total human genome
3
More than _______ tetranucleotide STR loci have been characterized in the human genome.
20,000
Why are satellite markers not typically used in forensics?
Large regions, surround the centromere, not easy to amplify with PCR
Why are minisatellite (VNTR) markers not typically used in forensics?
Not good for degraded DNA, if very large diff in size amplification with PCR would favor the
smaller strand
Why are microsatellite (STR) markers typically used in forensics?
occur frequently, highly variable, no differential amplification during PCR
Why are STR dinucleotide repeats not preferable units?
Too simple, can cause stutters during PCR
Simple repeat STR marker category
contain units of identical length and sequence
Simple repeats with non-consensus alleles STR marker category
contain incomplete repeat units (e.g. allele 9.3)
Compound repeat STR marker category
, contain two or more adjacent simple repeats
Complex repeat STR marker category
may contain several repeat blocks of variable unit length as well as variable intervening
sequences
What is a DNA profile?
a specific DNA pattern obtained from a person/sample of body tissue
What is another name for non-consensus alleles (incomplete repeat units)?
microvariants
T/F: Microvariants can often be confused with split peaks.
True
How many of the original 13 core loci overlap between US and Europe?
8
Combined DNA Index System (CODIS)
general term for the FBI's DNA database and the program used to run the databases
Nationa DNA Index System (NDIS)
part of CODIS maintained at the national level which contains DNA profiles contributed by
federal, state, and local labs
Why are 3 reasons to expand the CODIS core loci from 13 to 20?
1. reduce adventitious matches
2. inc. international compatibility
3. inc. discrimination power
How does Amelogenin determine sex?
X-chromosome contains 6 bp deletion, resulting in a 106 bp product whereas a Y-chromosome
contains a 112 bp product
What are the 4 components of the Pre-PCR portion of a STR Typing Kit?
1. Primer mix
2. PCR rxn buffer and dNTPs
3. DNA polymerase
4. control DNA
