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Although neutral evolution remains the consensus theory among modern biologists, [3] and thus Kimura's resolution of Haldane's dilemma is widely regarded as correct, some biologists argue that adaptive evolution explains a large fraction of substitutions in protein coding sequence, [4] and they propose alternative solutions to Haldane's dilemma.
In humans, barring intersex conditions causing aneuploidy and other unusual states, it is the male that is heterogametic, with XY sex chromosomes.. Haldane's rule is an observation about the early stage of speciation, formulated in 1922 by the British evolutionary biologist J. B. S. Haldane, that states that if — in a species hybrid — only one sex is inviable or sterile, that sex is more ...
In 1957, Haldane articulated Haldane's dilemma, a limit on the speed of beneficial evolution, an idea that is still debated today. [8] He is also remembered for his work in human biology, having coined "clone", "cloning", and "ectogenesis". With his sister, Naomi Mitchison, Haldane was the first to demonstrate genetic linkage in mammals.
If the gene is involved in growth, such as photosynthesis, the plant will experience increased vitality. [16] The results heterosis can be seen in traits such as increased fruit yield, earlier ripening, and heat tolerance. Heterosis has been shown to provide increased general growth and fruit yield in tomato plants. [17]
Cell growth in bioreactors depends on a wide range of environmental and physiological conditions such as substrate concentration. With regards to bioreactor cell growth, substrate refers to the nutrients that the cells consume and is contained within the bioreactor medium. Cell growth can either be substrate limited or inhibited depending on ...
Haldane's sieve is particularly relevant in situations where the effects of natural selection are strong and the beneficial mutations have a significant impact on an organism's fitness. According to Haldane's sieve, when a new advantageous mutation arises in a population, it initially occurs as a single copy (a de novo mutation ), borne by an ...
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In seed plants, the gametophyte is even more reduced (at the minimum to only three cells), gaining all its nutrition from the sporophyte. The extreme reduction in the size of the gametophyte and its retention within the sporophyte means that when applied to seed plants the term 'alternation of generations' is somewhat misleading: "[s]porophyte ...