The Kenya Medical Research Institute (Kemri) is building a forensic reference DNA database that will help the government track down murder suspects, missing persons, disaster victims and sex offenders.
This is according to results obtained after randomly collecting samples from consenting individuals from 20 ethno-linguistic groups in five coastal counties - Kwale, Kilifi, Taita Taveta, Tana River and Lamu. The collection took place over the past three years.
Ms Eva Aluvaala-Nambati, a scientist at Kemri who is leading the project, revealed that they have been going around the country collecting DNA from Kenyans of all ethnicities for the past three years.
"Despite its small size, the mitochondrial genome can be used to establish maternal family ties thanks to its maternal inheritance pattern," she said.
"A total of 323 samples have been collected from this region, but so far 131 samples have been analysed," she said.
She added that 98 percent of the people from whom they collected the samples were over the age of 18.
"We also collected data on marital status, occupation, level of education and whether the participants had any chronic diseases or family history, were smokers or consumed alcohol," she said.
Ms Aluvaala-Nambati was speaking at the ongoing 14th Kemri Annual Scientific and Health Conference.
Kemri explains that databases are used in forensics to estimate the expected frequency of genotypes and haplotypes (strength of evidence).
This means that a frequency estimate for a sample of African origin cannot be generated using a Caucasian or Asian database.
Therefore, high quality population-based databases facilitate a reliable frequency estimate for a random match.
The database will also be instrumental in identifying decedents and linking unknown decedents to their relatives.
Samples were collected from groups including Malakote, Shirazi and Taita (Wakisaghala, Wakisighau, Dawida).
The scientists also collected samples from Changaye, Wakifundi, Taveta, Makonde, Pemba, Segeju, Boni, Pokomo, Vumba, Sambaa, Pare, Chagaa, Zigua, Tswaka.
Among the Mijikenda, samples were collected from Digo, Duruma, Ribe, Giriama, Kambe, Chonyi, Kauma, Jibana and Rabai).
The researchers also collected Bajuni and Swahili samples.
According to Ms. Aluvaala-Nambati, the database will be created using mitochondrial DNA (mtDNA), which is the totality of hereditary information contained in human mitochondria.
Mitochondrial DNA has many special features, such as a high copy number in the cell, maternal inheritance, and a high mutation rate, which have made it attractive to scientists.
"The human mitogenome of 16,569 base pairs (bp) is small compared to the nuclear genome, which is three billion bp," said Ms. Aluvaala-Nambati, explaining that a single cell found in mitochondria can have hundreds to thousands of copies of MtDNA, compared to two copies of nuclear DNA per cell.
A base pair consists of two complementary DNA nucleotide bases that bind together to form a "rung on the DNA ladder.
DNA is made up of two strands that wrap around each other to resemble a twisted ladder - a shape known as a double helix.
According to the expert, a copy of the human genome consists of about three billion base pairs of DNA spread over 23 chromosomes.
Human chromosomes range in size from approximately 50 million to 300 million base pairs.
She also emphasised that MtDNA is inherited exclusively from the mother, with no contribution from the father, unlike nuclear DNA, which is inherited equally from both parents.
The senior scientist went on to explain that mitochondrial genome diversity can be described in terms of haplogroups.
"Haplogroup refers to a population group that shares one or more distinguishing mutations. This means that individuals from the same geographic region tend to cluster in the same haplogroup, and therefore haplogroups can be used to infer the biogeographic ancestry(s) of individuals," she said.
Ms Aluvaala-Nambati pointed out that the high copy number per cell, hundreds to thousands of copies, makes it ideal when DNA samples are degraded or old.
"No recombination occurs on MtDNA, which is transmitted exclusively by the mother, so it can be used to identify maternally related individuals," she said.
According to the expert, in missing person and disaster victim identification cases, MtDNA increases the number of potential relatives who can be tested, as maternal relatives have the same identical mitochondrial DNA.
"In cold cases, crime scene samples can be analysed to infer possible ancestry, providing investigative leads for detectives to use," she said.
