Mol Bio Sem 1

CODIS

A forensic database of repeat based DNA profiles used to match crime scene samples to known individuals.

STR

A short repeated DNA sequence whose repeat count differs among people.

VNTR

A longer repeated DNA sequence whose repeat count differs among people.

SNP

A one letter DNA difference at a specific position that varies across individuals.

Mendelian inheritance

Passing genetic variants from parents to children in predictable allele patterns.

Mutation rate

How often a DNA region changes from one generation to the next.

Back mutation

A change that restores a DNA site to an earlier state.

GEDmatch

A public site where people upload genetic data so relatives can be found through shared segments.

Forensic genetic genealogy

Using genome wide variant data to find relatives and then using family trees to narrow to a person.

Shared DNA segment

A stretch of DNA that two people share because it came from the same ancestor.

Recombination

The shuffling process in meiosis that breaks inherited DNA into smaller pieces over generations.

Centimorgan (cM)

A unit that approximates how likely recombination is between two points, used to estimate relatedness from shared segments.

SNP microarray

A chip that tests many known single base variant sites across the genome in one run.

Probe

A short fixed DNA sequence designed to bind only to a matching allele.

Hybridization

Binding between complementary DNA strands because their bases match.

Fluorescent labeling

Attaching dye signals to DNA so binding can be detected.

Scanner readout

Measuring fluorescence at each spot to call which alleles are present.

Illumina style SNP chip

Uses allele specific probes and fluorescence signals on a chip to call genotypes.

Affymetrix style SNP chip

Uses a dense probe array on a solid surface to detect which alleles the sample binds to.

Why distant relatives share less

Recombination shortens shared segments over many generations.

No CODIS match workflow

Create a genome wide variant profile, search genealogy databases for relatives, then narrow candidates with family trees.

Final confirmation

Collect a direct sample from the candidate and match repeat based markers to the crime scene profile.

DNA barcoding

Identifying a species by sequencing a short genetic region and comparing it to a reference database.

Reference library

A collection of known sequences linked to verified species identities.

Target region

The chosen DNA segment that differs enough between species to distinguish them.

Conserved region

A DNA segment that stays similar across species so primers can bind reliably.

Variable region

A DNA segment that differs across species and provides identifying signal.

Primer

A short DNA starter that defines where copying begins and ends.

PCR

A technique that makes many copies of a chosen DNA region so it can be analyzed.

Sanger sequencing

Determining sequence by making many fragments that end at different positions and reading them by size and color.

ddNTP

A nucleotide missing the 3 prime OH, so once added it stops further extension.

Chain termination

Stopping DNA synthesis at a base when a terminator nucleotide is incorporated.

End labeling

Marking fragments at their stopping base with a detectable tag.

Gel electrophoresis

Separating DNA fragments by size so shorter pieces travel farther.

Fluorescent detection

Reading emitted colors to identify which base ended each fragment.

BLAST

A search tool that compares a sequence to databases to find the closest matches.

Alignment

Lining sequences up to see where bases match and differ.

E value

A statistic estimating how likely a match would occur by chance in a database search.

Whole genome shotgun sequencing

Sequencing many random genome fragments and assembling them by overlap into a full genome.

Overlap assembly

Stitching fragments together using shared end sequences.

Next generation sequencing

Sequencing millions of fragments at once to produce massive parallel readouts.

Flow cell

A surface that holds many DNA fragments in place during copying and imaging.

Bridge amplification

Creating clusters of identical copies on the surface to strengthen signal.

Cluster

A tight group of identical DNA molecules that produces a measurable fluorescent signal.

Sequencing by synthesis

Reading bases as they are added during DNA copying cycles.

In situ sequencing

Keeping fragments fixed in one spot while copying and imaging to reduce handling and improve consistency.