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In sociology, heterogamy refers to a marriage between two individuals that differ in a certain criterion, and is contrasted with homogamy for a marriage or union between partners that match according to that criterion. For example, ethnic heterogamy refers to marriages involving individuals of different ethnic groups.
A study on guppies, Poecilia reticulata, revealed that the female preference was sufficient to tightly maintain polymorphism in male traits. [6] This type of mate choice shows that costly preferences can persist at higher frequencies if mate choice is hindered, which would allow the alleles to approach fixation.
A dominant allele can be inherited from a homozygous dominant parent with probability 1, or from a heterozygous parent with probability 0.5. To represent this reasoning in an equation, let A t {\displaystyle \textstyle A_{t}} represent inheritance of a dominant allele from a parent.
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 the XY sex-determination system, the female-provided ovum contributes an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female (XX) or male (XY) offspring, respectively. Hormone levels in the male parent affect the sex ratio of sperm in humans. [25]
It has been suggested that Haldane's rule simply reflects the fact that the male sex is more sensitive than the female when the sex-determining genes are included in a hybrid genome. But there are also organisms in which the heterozygous sex is the female: birds and butterflies and the law is followed in these organisms. Therefore, it is not a ...
Multiple studies have shown, in double-blind experiments, females prefer the scent of males who are heterozygous at all three MHC loci. [ 21 ] [ 22 ] The reasons proposed for these findings are speculative; however, it has been argued that heterozygosity at MHC loci results in more alleles to fight against a wider variety of diseases, possibly ...
There are fewer X-linked dominant conditions than X-linked recessive, because dominance in X-linkage requires the condition to present in females with only a fraction of the reduction in gene expression of autosomal dominance, since roughly half (or as many as 90% in some cases) of a particular parent's X chromosomes are inactivated in females.