How to tame a restless genome

Short pieces of DNA—jumping genes—can bounce from one place to another in our genomes. When too many DNA fragments move around, cancer, infertility, and other problems can arise. Cold Spring Harbor Laboratory (CSHL) Professor ...

Reproduction key to maintenance of marimo shape

The marimo is the aggregative form of the freshwater alga Aegagropila linnaei. In Japan, Lake Akan in Hokkaido is the best known habitat of the marimo. It is so emblematic of the lake and surrounding region that it has been ...

Sex as stress management in microbes

Why is sex so popular? The question of why so many organisms reproduce sexually has mystified evolutionary biologists since before Darwin, who wrote, "The whole subject is as yet hidden in darkness." In a recent article in ...

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Gamete

A gamete (from Ancient Greek γαμέτης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. 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 (or egg) — and a male produces the smaller tadpole-like type — called a sperm. This is an example of anisogamy or heterogamy, the condition wherein females and males produce gametes of different sizes (this is the case in humans; the human ovum is approximately 20 times larger than the human sperm cell). In contrast, isogamy is the state of gametes from both sexes being the same size and shape, and given arbitrary designators for mating type. The name gamete was introduced by the Austrian biologist Gregor Mendel. Gametes carry half the genetic information of an individual, one chromosome of each type. In humans, an ovum can carry only X chromosome (of the X and Y chromosomes), whereas a sperm can carry either an X or a Y; hence, it has been suggested that males have the control of the sex of any resulting zygote, as the genotype of the sex-determining chromosomes of a male must be XY and a female XX. In other words, due to the presence of the Y chromosome exclusively in the sperm, it is that gamete alone that can determine that an offspring will be a male.

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