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Gametes—also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. In those species that produce two morphologically distinct types of gametes, and in which a particular individual produces only one type, " females" of the species produce the larger gamete called an ovum (or egg) and " males" produce the smaller gamete termed (in animals) a spermatozoon (or sperm). The equivalent "male" structure in higher plants is called a pollen grain. Organs that produce gametes are called gonads in animals, and archegonia or antheridia in plants.Gametes are haploidHaploid cells have only one copy of each chromosome. Most fungi, and a few algae exist as haploid organisms. Plants and other algae switch between a haploid and a diploid or polyploid state, with one of the stages emphasized over the other. This is called cells; that is, they contain one complete set of chromosome2) Centromere. The point where the two chromatids touch, and where the microtubules attach. 3) Short arm. 4) Long arm. A chromosome is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening ns (the actual number varies from species to species). When two gametes unite (typically in animals, involving a sperm and an egg), they form a zygoteIn biology, a zygote is the result of fertilization. That is, two haploid cells—usually (but not always) a sperm cell from a male individual and an ovum or ovule from a female—merge into a single diploid cell called the zygote''. The zygote then undergoes—a cell having two complete sets of chromosomes and therefore diploidDiploid cells have two copies of each somatic chromosome (non-sex chromosomes), usually one from the mother and one from the father. Most somatic cells (body cells) of higher organisms are diploid or polyploid (three or more copies of each chromosome, oft. The zygote cell receives one set of chromosomes from each of the two gametes involved in the union. After fusion of the two gamete nucleiIn chemistry and physics, the nucleus atomic nucleus is the collection of protons and neutrons in the center of an atom that carries the bulk of the atom's mass and positive charge. In cell biology, the nucleus cell nucleus is the membrane-bound subcellul, and after multiple cell divisionCell division is the process of a biological cell (called a mother cell dividing into two daughter cells''. This leads to growth in multicellular organisms (the growth of tissue) and to procreation ( vegetative reproduction) in unicellular organisms.s and cellular differentiationCellular differentiation is a concept from developmental biology describing the process by which cells acquire a " type". The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptio, a zygote developsEmbryology Developmental biology is the study of the process by which organisms grow and develop. Originating in embryology, today developmental biology studies the genetic control of cell growth, differentiation and " morphogenesis," which is the process, first into an embryo, and ultimately into a mature individual capable of producing gametes. Gametes from a mature diploid individual will be produced in the gonadal tissue through meiosis—a process of cellular division that reduces the number of sets of chromosomes from two to one (i.e., produces haploid gametes).
The diploid somatic cells of an individual will contain one copy of the chromosome set from the sperm and one copy of the chromosome set from the egg—that is, the cells of the offspring will have genes expressing characteristics of both the "father" and the "mother". A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the somatic cells of the individual that produced the gametes. They can be "hybrids" produced through crossover (a form of genetic recombination) of chromosomes, something that takes place in meiosis. This hybridization has a random element and the chromosomes tend to be a little different in every gamete an individual produces. This recombination, and the fact that the two chromosome sets ultimately have come from either a grandmother or a grandfather on each parental side, account for the genetic dissimilarity of siblings.
