The Primary Mechanisms for Sex Determination Across the Animal Kingdom

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Manolakou et al. suggest that there are three primary mechanisms for sex determination across the animal kingdom. The first is environmental factors. Fish and Reptiles do not have chromosomes that determine the sex of the offspring. The temperature is the primary determinant. Some organisms’ sex will be determined by specific environmental factors like temperature during the right developmental stages of the embryo. This is referred to as the thermosensitive period (TSP). The second mechanism is when a specific gene is responsible for a cascade effect that will ultimately determine the sex of the offspring. This mechanism is seen in some invertebrates like insects, and amphibians. The single regulating gene has not yet been determined. The third mechanism is the occurrence of individual sex chromosomes like what we see in mammals. In mammals the males are heterozygous and the females are homozygous, but in birds the opposite is true, but birds still have distinct sex chromosomes. Some organisms have distinct sex determining chromosomes, but they have yet to be discovered. How or why certain organisms develop into certain gender is not necessarily known, but the idea that there could be some sort of governing pattern could lend itself useful to comparative biology and reproductive endocrinology. Haplodiploid genetic system is a very curious mechanism in insects. The insects can be either uniparental or biparental, meaning one parent or two. The females can
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