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Artificial Gametes
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum— and a male produces the smaller type—called a sperm. Sperm cells or spermatozoa are small and motile due to the flagellum, a tail-shaped structure that allows the cell to propel and move. In contrast, each egg cell or ovum is relatively large and non-motile. In short a gamete is an egg cell (female gamete) or a sperm (male gamete). In animals, ova mature in the ovaries of females and sperm develop in the testes of males. During fertilization, a spermatozoon and ovum unite to form a new diploid organism. Gametes carry half the genetic information of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ploidy
Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively, in each homologous chromosome pair, which chromosomes naturally exist as. Somatic cells, Tissue (biology), tissues, and Individual#Biology, individual organisms can be described according to the number of sets of chromosomes present (the "ploidy level"): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploidy, polyploid is often used to describe cells with three or more chromosome sets. Virtually all sexual reproduction, sexually reproducing organisms are made up of somatic cells that are diploid or greater, but ploidy level may vary widely between different or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eduard Strasburger
Eduard Adolf Strasburger (1 February 1844 – 18 May 1912) was a Polish-German professor and one of the most famous botanists of the 19th century. He discovered mitosis in plants. Life Eduard Strasburger was born in Warsaw, Congress Poland, the son of Krystyna Anna (von Schütz) and Edward Bogumił Strasburger (1803–1874).Klaus Oskar Leyde: Strasburger. In: Deutsches Geschlechterbuch Band 207 (56. Allgemeiner Band), C. A. Starke Verlag, Limburg 1998, S. 227–242. In 1870, he married Aleksandra Julia Wertheim (1847–1902), they had two children: Anna (1870–1942) and Julius (1871–1934). Strasburger studied biological sciences in Paris, Bonn and Jena, receiving a PhD in 1866 after working with Nathanael Pringsheim. In 1868 he taught at the University of Warsaw. In 1869 he was appointed professor of botany at the University of Jena. From 1881 he was head of the ''Botanisches Institut'' at the University of Bonn. Strasburger died in Bonn, Germany. Achievements Stras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dominance (genetics)
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new (''de novo'') or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes ( autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child (see Sex linkage). Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance such as incomplete d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosome
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are the histones. These proteins, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. These chromosomes display a complex three-dimensional structure, which plays a significant role in transcriptional regulation. Chromosomes are normally visible under a light microscope only during the metaphase of cell division (where all chromosomes are aligned in the center of the cell in their condensed form). Before this happens, each chromosome is duplicated ( S phase), and both copies are joined by a centromere, resulting either in an X-shaped structure (pictured above), if the centromere is located equatorially, or a two-arm structure, if the centromere is located distally. The joined copies are now called si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Somatic Cell
A somatic cell (from Ancient Greek σῶμα ''sôma'', meaning "body"), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Such cells compose the body of an organism and divide through the process of binary fission and mitotic division. In contrast, gametes are cells that fuse during sexual reproduction, germ cells are cells that give rise to gametes, and stem cells are cells that can divide through mitosis and differentiate into diverse specialized cell types. For example, in mammals, somatic cells make up all the internal organs, skin, bones, blood and connective tissue, while mammalian germ cells give rise to spermatozoa and ova which fuse during fertilization to produce a cell called a zygote, which divides and differentiates into the cells of an embryo. There are approximately 220 types of somatic cell in the human body. Theoretically, these cells are not germ cells (t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geoff Parker
Professor Geoffrey Alan Parker FRS (born 24 May 1944) is an emeritus professor of biology at the University of Liverpool and the 2008 recipient of the Darwin Medal. Parker has been called “the professional’s professional”. He has a particular interest in behavioural ecology and evolutionary biology, and is most noted for introducing the concept of sperm competition in 1970. Much of his work from the 1970s onwards has related to the application of game theory (theory of games) to various biological problems, using the evolutionarily stable strategy (ESS) approach pioneered by John Maynard Smith and George Price. With R. R. Baker and V. G. F. Smith in 1972, he proposed a leading theory for the evolution of anisogamy and two sexes, and in 1979 made the first theoretical analysis of sexual conflict in evolution. He has also investigated the evolution of competitive mate searching, animal distributions, animal fighting, coercion, intrafamilial conflict, complex life cycle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oogamy
Oogamy is an extreme form of anisogamy where the gametes differ in both size and form. In oogamy the large female gamete (also known as ovum) is immobile, while the small male gamete (also known as sperm) is mobile. Oogamy is a common form of anisogamy, with almost all animals and land plants being oogamous. Occurrence Oogamy is found in most species that reproduce sexually, all higher species being oogamous. Oogamy is found in all land plants, and in some red algae, brown algae and green algae. Oogamy is favored in plants because only one gamete has to travel through harsh environments outside the plant. Oogamy is also present in oomycetes. Almost all animals are oogamous. There are exceptions, such as the opiliones that have immobile sperm. Etymology The term oogamy was first used in the year 1888. Evolution It is generally accepted that isogamy is the ancestral state and that oogamy evolves from isogamy through anisogamy. However, transitions do exist between ani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatozoon
A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a female (XX) offspring, while one bearing a Y chromosome will lead to a male (XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677. Mammalian spermatozoon structure, function, and size Humans The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby dec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatocyte
Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and secondary spermatocytes. Primary and secondary spermatocytes are formed through the process of spermatocytogenesis. Primary spermatocytes are diploid (2N) cells. After meiosis I, two secondary spermatocytes are formed. Secondary spermatocytes are haploid (N) cells that contain half the number of chromosomes. In all animals, males produce spermatocytes, even hermaphrodites such as ''C. elegans'', which exist as a male or hermaphrodite. In hermaphrodite ''C. elegans'', sperm production occurs first and is then stored in the spermatheca. Once the eggs are formed, they are able to self-fertilize and produce up to 350 progeny. Development At puberty, spermatogonia located along the walls of the seminiferous tubules within the testis will be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatogenesis
Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are called spermatogonial stem cells. The mitotic division of these produces two types of cells. Type A cells replenish the stem cells, and type B cells differentiate into primary spermatocytes. The primary spermatocyte divides meiotically (Meiosis I) into two secondary spermatocytes; each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II. The spermatids are transformed into spermatozoa (sperm) by the process of spermiogenesis. These develop into mature spermatozoa, also known as sperm cells. Thus, the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa and four haploid cells. Spermatozoa are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Cell
The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non-motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized the oosphere becomes the oospore. When egg and sperm fuse during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living nimal comes froman egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals also reproduced via ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
