Fertilization
Developmental Biology · Physiology · Human Anatomy
Say it: fur-tuh-luh-ZAY-shun
Fertilization is the fusion of a sperm and an egg, the male and female gametes, into a single diploid cell, the zygote, that can develop into a new organism.
UK spelling: fertilisation
Also: conception, syngamy
Definition
What is fertilization?
Fertilization joins two haploid gametes, each carrying one set of chromosomes, into a diploid zygote with two sets, one from each parent. It restores the chromosome number halved by meiosis, combines the genetic material of two individuals and triggers the egg to begin development. In humans it normally happens in the outer part of the uterine tube, within about a day of ovulation, because the released egg survives only briefly.
Sperm must first be primed in the female tract, a step called capacitation. When a sperm binds the zona pellucida, the glycoprotein coat around the egg, its acrosome releases enzymes that clear a path, and the two cell membranes fuse. The egg then blocks other sperm: a rapid change in its membrane acts first, and a slower cortical reaction, in which granules under the membrane release their contents, seals the barrier. If more than one sperm enters, a condition called polyspermy, the embryo cannot survive. The egg also completes meiosis II, and the sperm and egg pronuclei come together.
Fertilization can also be carried out in the laboratory by in vitro fertilization, and in flowering plants it follows pollination.
Word parts
Where does the word “fertilization” come from?
- fertil-
- fruitful, able to bear offspringLatin fertilis, from ferre (to bear)
Practice it
Where you'll meet it
Related
Terms that go with it
- GameteA gamete is a haploid reproductive cell, such as a sperm or an egg, that fuses with a gamete of the opposite type at fertilization to form a zygote.
- MeiosisMeiosis is a two-stage cell division that turns one diploid cell into four genetically different haploid cells, the precursors of eggs and sperm.
- ChromosomeA chromosome is a thread-like structure of DNA and protein that carries an organism's genes; most human cells hold 46 of them in 23 pairs.
- GastrulationGastrulation is the stage of early embryonic development in which cells move and fold to turn a simple ball or disc of cells into three germ layers.
- Embryonic stem cellAn embryonic stem cell is a pluripotent stem cell taken from the inner cell mass of an early embryo, the blastocyst, and able to form every type of body cell.
- PollinationPollination is the delivery of pollen to the female reproductive parts of a seed plant, the step that makes fertilization and seed formation possible.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 43.6 Fertilization and Early Embryonic Development
- OpenStax Anatomy and Physiology 2e, 28.1 Fertilization
- NCBI MeSH: Fertilization
Last updated
Spotted a mistake? Tell us and we'll correct it.
Practice Developmental Biology
Free developmental biology quizzes, with an explanation for every answer.
See the Quizzes