DNA Time Team
via www.sanger.ac.uk and www.ebi.ac.uk
this activity looks at how digging into DNA can reveal aspects of our ancestry/evolution. The activity encourages visitors to work out the sequence of a common ancestor by filling in the gaps on a simple evolutionary tree.
Key messages of the activity:
• Genomes allow us to trace the evolutionary history of humans.
• Natural selection has helped to shape our genomes.
Supporting information on evolution and genetics
By comparing genomes of humans and apes we can trace the evolutionary history of humans and improve understanding of human disease.
Researchers have generated the genome sequences from humans, gorillas, chimpanzees and other apes. By comparing DNA we can see what changes make us different from our closest non-human relatives, the apes.
Using DNA sequencing we can see what changes in DNA explain the differences between people from various areas of the world. This knowledge of the genetic differences between individuals enables us to improve our understanding of the influence genetics has on human health and disease. For example, why are some people more likely to develop diabetes than others?
Three examples of genes shaped by selection in humans:
Caspase 12 (CASP12)
Located on chromosome 11, Caspase 12 belongs to a family of proteases that process proteins involved in inflammation. Some Africans have the active form whereas the majority of human populations have a shorter inactive form. The shorter inactive form of caspase 12 appears to protect against severe sepsis (a bacterial infection of the blood). Therefore this shorter inactive form of the gene may have given some survival advantage to individuals who had it. The expansion of humans out of Africa led to an increased exposure to more infection causing pathogens. Therefore the potential benefit of the full active form of caspase 12 was outweighed by the enhanced susceptibility to sepsis.
Duffy blood group, chemokine receptor (DARC/FY)
A growing number of human genes are involved in resistance to malaria, a disease that kills over a million people each year. One such gene is DARC that is located on chromosome 1 in humans and is involved in the entry of the malaria parasite into red blood cells. Humans that are Duffy blood group negative have a variant (FY*0) of the DARC gene. Individuals with two copies of the FY*0 variant do not express the DARC antigen on their red blood cells. As a result they are highly resistant to infection by the malaria parasite. The FY*0 allele is very common in Africa but rare outside.
Ectodysplasin A receptor (EDAR)
EDAR, is a gene involved in the development of hair, teeth and exocrine glands. It is located on chromosome 2 and shows strong evidence for positive selection in East Asians. A mutation in this gene at amino acid 370 that substitutes Valine for Alanine (V370A) reaches near fixation in Asia. This variant is absent in Europe and Africa and has been proposed as the target of selection. Its biological significance is unclear but the change is associated with thick hair and shovel-shaped incisors and may have been sexually selected.
DNA Time Team
via www.sanger.ac.uk and www.ebi.ac.uk
this activity looks at how digging into DNA can reveal aspects of our ancestry/evolution. The activity encourages visitors to work out the sequence of a common ancestor by filling in the gaps on a simple evolutionary tree.
Key messages of the activity:
• Genomes allow us to trace the evolutionary history of humans.
• Natural selection has helped to shape our genomes.
Supporting information on evolution and genetics
By comparing genomes of humans and apes we can trace the evolutionary history of humans and improve understanding of human disease.
Researchers have generated the genome sequences from humans, gorillas, chimpanzees and other apes. By comparing DNA we can see what changes make us different from our closest non-human relatives, the apes.
Using DNA sequencing we can see what changes in DNA explain the differences between people from various areas of the world. This knowledge of the genetic differences between individuals enables us to improve our understanding of the influence genetics has on human health and disease. For example, why are some people more likely to develop diabetes than others?
Three examples of genes shaped by selection in humans:
Caspase 12 (CASP12)
Located on chromosome 11, Caspase 12 belongs to a family of proteases that process proteins involved in inflammation. Some Africans have the active form whereas the majority of human populations have a shorter inactive form. The shorter inactive form of caspase 12 appears to protect against severe sepsis (a bacterial infection of the blood). Therefore this shorter inactive form of the gene may have given some survival advantage to individuals who had it. The expansion of humans out of Africa led to an increased exposure to more infection causing pathogens. Therefore the potential benefit of the full active form of caspase 12 was outweighed by the enhanced susceptibility to sepsis.
Duffy blood group, chemokine receptor (DARC/FY)
A growing number of human genes are involved in resistance to malaria, a disease that kills over a million people each year. One such gene is DARC that is located on chromosome 1 in humans and is involved in the entry of the malaria parasite into red blood cells. Humans that are Duffy blood group negative have a variant (FY*0) of the DARC gene. Individuals with two copies of the FY*0 variant do not express the DARC antigen on their red blood cells. As a result they are highly resistant to infection by the malaria parasite. The FY*0 allele is very common in Africa but rare outside.
Ectodysplasin A receptor (EDAR)
EDAR, is a gene involved in the development of hair, teeth and exocrine glands. It is located on chromosome 2 and shows strong evidence for positive selection in East Asians. A mutation in this gene at amino acid 370 that substitutes Valine for Alanine (V370A) reaches near fixation in Asia. This variant is absent in Europe and Africa and has been proposed as the target of selection. Its biological significance is unclear but the change is associated with thick hair and shovel-shaped incisors and may have been sexually selected.