1. Q: Why are there two sexes?
From Genome to Life:
Structural, Functional and Evolutionary Approaches
Cargèse, Corsica July , 2002
Marc Fellous:
Q: Why are there two sexes?

2. Inter-membrane
space I II
III IV
ATPase
Matrix

3. The mitochondrial theory of ageing
Figure from:
ALLEN, J F (1996) J. Theor. Biol. 180,

5. Problem
The Mitochondrial Theory of Ageing predicts that offspring should inherit their mother’s acquired state of accumulated damage, but they evidently do not.
Babies are not born at the age of their mothers.
How can this be?

6. Proposed solution (hypothesis)
Separate sexes allows specialisation of mitochondria either as genetic templates (female germ line) or as energy-transducing organelles performing oxidative phosphorylation (male germ line)
ALLEN, J F (1996) J. Theor. Biol. 180,

8. Predictions
Explanations of previous knowledge
Mitochondria are maternally inherited
Females have a time-limited reproductive activity - oocyte mitochondria become useless as genetic templates after a certain threshold of oxidative damage is reached
Oocyte mitochondria are energetically disabled - permanently.
Experimental predictions
Many…. E.g life-cycle of a germ-line mitochondrion
Science and society
Male and female are unequal but COMPLEMENTARY

9. Q: Why are there two sexes? John Allen:
From Genome to Life:
Structural, Functional and Evolutionary Approaches
Cargèse, Corsica July , 2002
Marc Fellous:
Q: Why are there two sexes?
John Allen:
A: Division of labour to resolve the dilemma of mitochondria - energy convertion (male) OR fidelity of replication of mtDNA (female)
Vive la différence…….