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The sperm plasma then fuses with the egg's plasma membrane and their nuclei fuse, triggering the sperm head to disconnect from its flagellum as the egg travels down the fallopian tube to reach the uterus. In vitro fertilization (IVF) is a process by which egg cells are fertilized by sperm outside the womb, in vitro.
A female produces an ovum with a full set (two sets of genes) provided solely by the mother. Thus, a male is not needed to provide sperm to fertilize the egg. This form of asexual reproduction is thought in some cases to be a serious threat to biodiversity for the subsequent lack of gene variation and potentially decreased fitness of the offspring.
During sexual intercourse, sperm cells are ejaculated into the vagina through the penis, resulting in fertilization of an ovum to form a zygote. [1] While normal cells contain 46 chromosomes (23 pairs), gamete cells contain only half that number, and it is when these two cells merge into one combined zygote cell that genetic recombination occurs.
Creating female sperm was first raised as a possibility in a patent filed in 1991 [4] by injecting a female's cells into a male's testicles, though the patent focused mostly on injecting altered male cells into a male's testes to correct genetic diseases. In 1997, Japanese scientists partially confirmed such techniques by creating chicken ...
When an egg and sperm fuse at fertilization, the two sets of chromosomes come together to form a unique diploid individual with 46 chromosomes. [2] The sex chromosome in a human egg is always an X chromosome since a female only has X sex chromosomes. In sperm, about half the sperm have an X chromosome and half have a Y chromosome. [2]
Since the male's gametes are energetically cheap and abundant in every ejaculation, a male can greatly increase his sexual success by mating far more frequently than the female. [21] Sperm, unlike egg cells, are also mobile, allowing for the sperm to swim towards the egg through the female's sexual organs.
The human reproductive system includes the male reproductive system, which functions to produce and deposit sperm, and the female reproductive system, which functions to produce egg cells and to protect and nourish the fetus until birth. Humans have a high level of sexual differentiation.
Cryptic female choice is a form of mate choice which occurs both in pre- and post-copulatory circumstances in which females of certain species use physical or chemical mechanisms to control a male's success of fertilizing their ova or ovum; i.e. by selecting whether sperm are successful in fertilizing their eggs or not.