Chapter 23: Mitochondrial DNA Profiling

Mitochondria

Are cellular organelles that serve as the energy-generating components of cells.

Cambridge reference sequence (CRS)

The sequence was largely derived from a placental sample from an individual of European descent and also partially from HeLa cells and bovine cells.

revised Cambridge reference sequence

The _______ (rCRS) was published in 1999 and presented corrections to these substitution errors.

Control Region

also known as Displacement Loop; it contains the origin of replication for one of the mtDNA strands but does not code for any gene products.

Maternal inheritance

is typically observed for the mtDNA genome, which is inherited differently from nuclear genes.

non-Mendelian inheritance

The inheritance of the mtDNA genome does not obey the rules of Mendelian inheritance and is thus called ______.

Mitotype

Considered a haplotype treated as a single locus.

D-loop

The most polymorphic region of mtDNA is located within the ______.

Heteroplasmy

________ occurs when an individual carries more than one mtDNA haplotype.

Sequence heteroplasmy

The presence of two different nucleotides at a single position shown as overlapping peaks in a sequence electropherogram.

Light heteroplasmy

Are often observed at the uninterrupted C stretches in sequencing, in which sequencing products with various lengths of polymeric cytosine residues are present.

ASO Assay

It allows initial screening of mtDNA sequence polymorphisms and has the potential to reduce the number of samples required for mtDNA sequencing.

Linear Array™ mtDNA HV1/HV2 region sequence typing kit

It utilizes reverse ASO configuration with a panel of immobilized ASO probes that detect common polymorphic sites.

Chain-Termination or Sanger Method

An oligonucleotide primer that can anneal to a singlestranded DNA template is utilized.

Cycle Sequencing

It utilizes thermal cycling to generate a single-stranded template for chain-termination sequencing reactions.

Reporting Format

Sequence differences relative to the rCRS are listed in data format.

Insertions

Described by noting the position followed by a decimal point and a number.

Deletions

These site designation is followed by letter d.

Exclusion

If the sequences of questioned and known samples are different, then the samples can be excluded as originating from the same source.

Cannot Exclude

If the sequences are the same, the reference sample and evidence cannot be excluded as arising from the same source.

Inconclusive Result

If the questioned and known samples differ by a single nucleotide, and no heteroplasmy is present.