This is similar to the bald head gene in human. The trait is dominant, but only men can be bald. It is because even the women have the allele, but they do not have the male sex hormone, so, women would not express the bald head.
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(25.12.2006)
| (1) | Mitochondrion and chloroplast have their own genetic materials. So, their inheritances are not affected by the individual. | ||
| (2) | Cytoplasmic DNA can give some inheritance characteristics. It is located in cytoplasm and outside the nucleus. Normally, this type of DNA would have bigger influence in the developing zygote. | ||
| (3) | Something can affect the expression of genes by other chemicals, as sex hormone. In a type of sheep, whether it can have horn is determined by the horned gene and the male sex hormone. The horned trait is dominant. The purebred recessive individual would have no horn. But even the female sheep possess the horned allele, she cannot have horn, because there is no male sex hormone. This is similar to the bald head gene in human. The trait is dominant, but only men can be bald. It is because even the women have the allele, but they do not have the male sex hormone, so, women would not express the bald head.
(25.12.2006) |