Chapter 8 Short Tandem Repeat Markers - Vocabulary Flashcards

50 vocabulary flashcards covering key STR concepts from the lecture notes.

Short Tandem Repeat (STR)

A DNA sequence in which a short motif (2–7 bp) is repeated in tandem and is highly polymorphic, often analyzed by PCR.

Microsatellite

A class of repetitive DNA sequences; STRs are a subset characterized by short, tandemly repeated units.

Minisatellite (VNTR)

Longer repeat units (8–100 bp) and overall variable region; older forensic markers like D1S80.

Satellite DNA

Large, tandemly repeated DNA sequences that may surround centromeres and form heterochromatin.

Core Repeat Unit

The actual repeating DNA sequence length that defines an STR (e.g., 4 bp for tetranucleotides).

Simple Sequence Repeats (SSRs)

Another name for short tandem repeats.

Dinucleotide Repeat

STR with a two-nucleotide repeat unit (e.g., CA)n.

Trinucleotide Repeat

STR with a three-nucleotide repeat unit (e.g., CAG)n.

Tetranucleotide Repeat

STR with a four-nucleotide repeat unit; the most popular for forensic STR typing.

Pentanucleotide Repeat

STR with a five-nucleotide repeat unit.

Hexanucleotide Repeat

STR with a six-nucleotide repeat unit.

D2S1338

One of the CODIS core autosomal STR loci used in forensic DNA typing.

Allelic Ladder

An artificial mixture of common alleles at a locus used as a sizing reference in STR analysis.

CODIS

The Combined DNA Index System; the U.S. national database of DNA profiles using core STR loci.

13 CODIS Core Loci

The set of 13 autosomal STR loci used in CODIS for identity testing.

CSF1PO

A CODIS core STR locus; tetranucleotide repeat.

FGA

A CODIS core STR locus at the fibrinogen alpha gene; tetranucleotide repeat.

TH01

A CODIS core STR locus at the tyrosine hydroxylase gene; tetranucleotide repeat.

TPOX

A CODIS core STR locus at the thyroid peroxidase gene; tetranucleotide repeat.

VWA

A CODIS core STR locus at the von Willebrand factor gene; tetranucleotide repeat.

D3S1358

A CODIS core STR locus; tetranucleotide repeat.

D5S818

A CODIS core STR locus; tetranucleotide repeat.

D7S820

A CODIS core STR locus; tetranucleotide repeat.

D8S1179

A CODIS core STR locus; tetranucleotide repeat.

D13S317

A CODIS core STR locus; tetranucleotide repeat.

D16S539

A CODIS core STR locus; tetranucleotide repeat.

D18S51

A CODIS core STR locus; tetranucleotide repeat.

D21S11

A CODIS core STR locus; tetranucleotide repeat.

Amelogenin

Sex-determining marker used with STR analysis; X and Y chromosome amplicons indicate gender.

Amelogenin Y-Dropout

Rare case where Y-specific amelogenin amplicon fails, potentially yielding a female result for a male sample.

Amelogenin Anomaly

Irregular amelogenin results due to sequence variation or assay limitations.

Stutter

A PCR artifact where the product is typically one repeat shorter than the true allele.

Microvariant

Allele containing an incomplete or partial repeat within the STR region.

Allele Dropout

Failure to detect one allele in a heterozygote, often due to degraded DNA or preferential amplification.

Flanking Regions

DNA sequences adjacent to the STR; where primers bind for PCR amplification.

PCR Primers

Short DNA sequences that flank the STR and initiate amplification of the target region.

Capillary Electrophoresis

Technique used to separate PCR products by size, enabling allele sizing in STR analysis.

Five-Dye Detection

A labeling system using five fluorescent dyes to enable multiplex STR analysis.

Mobility Modifiers

Chemical linkers added to primers to shift the mobility of PCR products during electrophoresis.

Non-Nucleotide Linker (HEO)

A nonstandard linker used to alter allele mobility in STR kits.

PowerPlex 16

Promega multiplex kit that amplifies 16 STR loci plus amelogenin.

Identifiler

Applied Biosystems multiplex kit enabling co-amplification of 15 STR loci and amelogenin with five-dye detection.

STRBase

Internet database for STR information, references, and resources maintained by NIST.

ISFG Recommendations

Guidelines from the International Society for Forensic Genetics on STR nomenclature and motif designation.

Top Strand vs Bottom Strand

Strand choice affects STR motif designation; ISFG recommends using the top strand.

Allele Designation Nomenclature

Standard system for naming STR alleles by repeat count and core motif.

Degraded DNA / MiniSTR

Small-amplicon STRs designed for degraded samples.

Random Match Probability

Probability that a random person would have the same STR profile; used to assess rarity.

Population Data

Allele frequencies across populations used to calculate match probabilities.

SE33 (ACTBP2)

A complex hypervariable STR locus included in some STR panels.