Presentation on theme: "Where do we come from?. -Homo erectus evolved in Africa and spread to the rest of the world ~1-2 million years ago. Where do we come from? 1. Multiregional."— Presentation transcript:
-Homo erectus evolved in Africa and spread to the rest of the world ~1-2 million years ago. Where do we come from? 1. Multiregional evolution 2. Recent African origin Two main hypothesis: What about the evolution of the modern humans?
Human Genetics -Human genome contains about 30,000 genes. -The haploid human genome occupies a total of just over 3 billion DNA base pairs. Mutations in human DNA are used to show relationships and evolutionary history.
What are Mitochondria? -They are responsible for making ATP, the cell energy-coin -Mitochondria are organelles living inside the cell
Where do Mitochondria come from? - Originally from small bacteria swallowed by larger bacteria. phagocytosis
How do we know they evolved from bacteria? -They have there own circular genome, like bacteria -Double membrane: Original + Phagosome -Protein-synthesis machinery resembles bacteria - And more...
How are Mitochondria passed during fertilization? Both men and women possess mtDNA, but only women pass it on to their children. While female eggs contain lots of mitochondria, male sperm contains only a few, which are destroyed after fertilization. When cells divide, mitochondria are divided as well
mtDNA Therefore, the mitochondria that we have are passed down from mother to children
The human mitochondrial genome The rate at which mutations occur in nuclear DNA is extremely low (~only one in one thousand million will mutate at every cell division). In mitochondria, about twenty times as many mutations.
Chromosomes Mitochondrial genome Vs. 16,500bp 3 billion bp Inherited from both parents Inherited from the mother Error –checking mechanisms Mutation rate: 1 in 1,000,000,000 High mutation rate (10 -4 )
We can determine common ancestral mothers by changes in the sequence of the mitochondrial genome
African Eve or the Mitochondrial Eve Many researchers take the mitochondrial evidence as support for the "single-origin" or Out-of-Africa model The existence of the Mitochondrial Eve is NOT a theory; it is a mathematical fact