Sex - Sexual Reproduction

Sexual Reproduction

(Also see Isogamy and Anisogamy)

Sexual reproduction in eukaryotes is a process whereby organisms form offspring that combine genetic traits from both parents. Chromosomes are passed on from one generation to the next in this process. Each cell in the offspring has half the chromosomes of the mother and half of the father. Genetic traits are contained within the deoxyribonucleic acid (DNA) of chromosomes – by combining one of each type of chromosomes from each parent, an organism is formed containing a doubled set of chromosomes. This double-chromosome stage is called "diploid", while the single-chromosome stage is "haploid". Diploid organisms can, in turn, form haploid cells (gametes) that randomly contain one of each of the chromosome pairs, via meiosis. Meiosis also involves a stage of chromosomal crossover, in which regions of DNA are exchanged between matched types of chromosomes, to form a new pair of mixed chromosomes. Crossing over and fertilization (the recombining of single sets of chromosomes to make a new diploid) result in the new organism containing a different set of genetic traits from either parent.

In many organisms, the haploid stage has been reduced to just gametes specialized to recombine and form a new diploid organism; in others, the gametes are capable of undergoing cell division to produce multicellular haploid organisms. In either case, gametes may be externally similar, particularly in size (isogamy), or may have evolved an asymmetry such that the gametes are different in size and other aspects (anisogamy). By convention, the larger gamete (called an ovum, or egg cell) is considered female, while the smaller gamete (called a spermatozoon, or sperm cell) is considered male. An individual that produces exclusively large gametes is female, and one that produces exclusively small gametes is male. An individual that produces both types of gametes is a hermaphrodite; in some cases hermaphrodites are able to self-fertilize and produce offspring on their own, without a second organism.

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Other articles related to "sexual reproduction, reproduction, sexual":

Mating In Fungi - Mating Type
... Sexual reproduction thereby depends on pheromones produced from variant alleles of the same gene ... Since sexual reproduction takes place in haploid organisms, it cannot proceed until complementary genes are provided by a suitable partner through cell or hyphal fusion ... Depending of the species, sexual reproduction takes place through gametes or hyphal fusion ...
Meiome - Origin and Function - Function
... eukaryotes (protists) generally can reproduce asexually (vegetative reproduction) or sexually, depending on conditions ... Asexual reproduction involves mitosis, and sexual reproduction involves meiosis ... When sex is not an obligate part of reproduction, it is referred to as facultative sex ...
Sexual Reproduction - Animals - Fish
... One fish species does not reproduce by sexual reproduction but uses sex to produce offspring Poecilia formosa is a unisex species that uses a form of parthenogenesis ...
Phaeodactylum Tricornutum
... Another peculiarity is that during asexual reproduction the frustules do not appear to decrease in size ... This allows continuous culture without the need for sexual reproduction ... tricornutum is capable of sexual reproduction ...
Red Queen (Through The Looking-Glass) - Adaptive Uses Outside The Arts - Red Queen's Hypothesis
... two different phenomena the advantage of sexual reproduction at the level of individuals, and the constant evolutionary arms race between competing species ... an experiment when mixing mother's and father's genes, sexual reproduction may allow a species to evolve quickly just to hold onto the ecological niche that it already occupies in the ecosystem ... writer Matt Ridley popularized the term "the red queen" in connection with sexual selection in his book The Red Queen ...

Famous quotes containing the word reproduction:

    The atmosphere parents wish to create when talking with children about birth and reproduction is warm, honest, and reassuring, one that tells children they are free to ask questions as often as they need to, and you will answer them as lovingly as you know how.
    Joanna Cole (20th century)