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J. theor. Biol. (1996) 180, 135140 00225193/96/100135 + 06 $18.00/0 7 1996 Academic Press Limited
 

Summary: J. theor. Biol. (1996) 180, 135140
00225193/96/100135 + 06 $18.00/0 7 1996 Academic Press Limited
Separate Sexes and the Mitochondrial Theory of Ageing
JOHN F. ALLEN
Department of Plant Cell Biology, Lund University, Box 7007, S-220 07 LUND, Sweden
(Received on 16 June 1995, Accepted in revised form on 15 December 1995)
An hypothesis is presented by which gamete specialization resolves a conflict between the function and
replication of mitochondria. The function of mitochondria is to synthesize ATP by oxidative
phosphorylation, which is coupled to respiratory electron transport. This requires a mitochondrial
genetic system. However, ``incorrect'' electron transfers produce free radicals that cause mutation, and
the frequency of these events is increased by mutation. Mitochondrial function is therefore detrimental
to the fidelity of mitochondrial replication. Damage to somatic mitochondrial DNA may accumulate
within, and indeed determine, the life span of individual organisms. Motility of one gamete is required
for fertilization, and requires ATP. It is proposed that male gametes maximize energy production for
motility by sacrificing mitochondrial DNA to electron transfer and its mutagenic by-products, while
female gametes, which are non-motile, repress mitochondrial oxidative phosphorylation, thus protecting
mitochondrial DNA for faithful transmission between generations. Male gametes then make no
contribution to the mitochondrial genome of the zygote: mitochondria are maternally inherited. This
testable hypothesis may help to explain the evolution of separate sexes and a number of their
characteristics. Maternal inheritance of chloroplasts may be explained in a similar way, and contribute

  

Source: Allen, John F. - School of Biological and Chemical Sciences, Queen Mary, University of London

 

Collections: Renewable Energy; Biology and Medicine