Cytogenetics Notes

2000 and the associated inheritance modes of the

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Unformatted text preview: haw et al. (2000) and the associated inheritance modes of the chloroplasts and the mitochondria (Mogensen er or lower evoluti 1996). ‘‘P’’ represents paternal inheritance, ‘‘M’’ maternal inheritance, or paternal organel ‘‘cp’’ chloroplast, and ‘‘mt’’ mitochondrion. The symbol ‘‘?’’ means One challenge not known with certainty. Cupressaceae s.l. (sensu lato) includes the tochondrial and ch Taxodiaceae. current lack of DN ysis. Even though lutionar y rates of male- versus female-inherited DNA to be readily avail should be investigated. al. 1992; Gadek an The rate of substitution of selectively neutral DNA Morgan and Soltis (introns, intergenic DNA, synonymous sites of coding remain less so. Th DNA) should be equal to the mutation rate (Kimura particularly suitabl 1983; Li 1997). The comparison of evolutionar y rates cause it is known of male- versus female-inherited neutral DNA in plants bution in land plan could therefore help determine the relative mutation rate species (Besendahl inherent to sperm versus eggs. Although most plants do have been describe not have sex chromosomes (Ginkgo is an exception), segments in a dive Mitochondrial and chloroplast DNAs evolve faster in plants in which the corresponding organelle is inherited through the pollen (male parent) than in species in which it is inherited through ovules (female parent). Implications of Meiosis and Gametogenesis #3 Genetic Diversity: novel combinations of alleles • 23 chromosome pairs in humans • Possible combinations of chromosomes in a gamete = 223 or ca. 8 million • The number of possibilities become essentially infinite when considering the possible cross-overs within chromosomes Implications of Meiosis and Gametogenesis #4 Mating within a single meiosis and the effects of sampling without replacement In the parasitic fungus Microbotryum (anther smut), spores undergo meiosis, and the four resulting gametes from a single meiosis usually mate with each other. A A a a Source: Hood and Antonovics 2000 Heredity a A A 1 1 A a 1 1 a AA Aa Aa 1 2 1 Implications of Meiosis and Gametogenesis #4 Mating within a single meiosis and the effects of sampling without replacement In the parasitic fungus Microbotryum (anther smut), spores undergo meiosis, and the four resulting gamet...
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