Nonidentical twins occur when a woman produces two separate eggs that are then fertilized by two different sperm cells. The resulting twins sometimes look alike, but have separate genetic identities, like children of the same parents born during different pregnancies. Another name for nonidentical twins is fraternal twins.Know More
Nonidentical twins only form when two eggs release during the same ovulation. In some cases, the eggs release simultaneously. In others, the ovaries initially release one egg. After fertilization that egg begins moving to the uterus to attach. The ovaries then release a second egg, fertilized by a later act of sexual intercourse. This leads to the potential of a woman giving birth to nonidentical twins with two separate fathers. In this case, the genetic identity of the twins is the same as a half-sibling born from separate pregnancies.
The sex of fraternal twins has a chance of differing. Identical twins develop when a single egg fertilized by a single sperm splits to form two different babies. These twins have the same genetic identity. Identical twins are always the same sex.
While some women produce multiple eggs with every ovulation, others begin producing multiple eggs as they grow older. Genetics also plays a role in the chance of conceiving twins. Use of fertility drugs increases the chance of producing more than one egg during each cycle.Learn more about Biology
It might sound like a wayward twist from a movie, but it is possible for fraternal (not identical) twins to come from two different dads. The circumstances must be very specific, but some experts estimate that 1-2 percent of fraternal twins have different fathers.Full Answer >
Medical professionals use the phrase "gravida 2 para 1" to refer to a woman who has been pregnant a total of two times and carried only one of those pregnancies to the age of viability. Gravida refers to the number of times the woman has been pregnant. Para refers to the number of pregnancies resulting in a birth whether the birth was stillborn or living.Full Answer >
Non-motile bacteria are bacteria that show no motion. They lack the ability to swim toward optimal areas for survival, and they don't swim away from toxicity or toward nutrients and optimal light concentrations. This purposeful, spontaneous form of movement that most bacteria engage in is nonexistent in this form of bacteria.Full Answer >
Non-allosteric enzymes are a subset of enzymes that do not have an allosteric binding site in addition to the active site. These enzymes change in function solely due to the binding of a substrate to the active site and do not require the binding of allosteric modulators.Full Answer >