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When in a hypotonic solution, water flows into the membrane and increases the cell's volume, while in an isotonic solution, water flows in and out of the cell at an equal rate. [4] Turgidity is the point at which the cell's membrane pushes against the cell wall, which is when turgor pressure is high. When the cell has low turgor pressure, it is ...
Also meganucleus. The larger of the two types of nuclei which occur in pairs in the cells of some ciliated protozoa. Macronuclei are highly polyploid and responsible for directing vegetative reproduction, in contrast to the diploid micronuclei, which have important functions during conjugation. macrophage Any of a class of relatively long-lived phagocytic cells of the mammalian immune system ...
It is the stage of the life cycle when a cell gives rise to haploid cells each having half as many chromosomes as the parental cell. Two such haploid gametes, ordinarily arising from different individual organisms, fuse by the process of fertilization, thus completing the sexual cycle. Meiosis is ubiquitous among eukaryotes.
Regulation of gene expression, or gene regulation, [1] includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental ...
All living cells have the ability to receive and process signals that originate outside their membranes, which they do by means of proteins called receptors, often located at the cell's surface imbedded in the plasma membrane. When such signals interact with a receptor, they effectively direct the cell to do something, such as dividing, dying ...
In this image, a gene from one bacterial cell is moved to another bacterial cell. This process of the second bacterial cell taking up new genetic material is called transformation. In molecular biology and genetics , transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic ...
Synapsis during Meiosis. The circled area is the part where synapsis occurs, where the two chromatids meet before crossing over. Synapsis or Syzygy is the pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them.
In molecular biology and genetics, transcriptional regulation is the means by which a cell regulates the conversion of DNA to RNA (transcription), thereby orchestrating gene activity. A single gene can be regulated in a range of ways, from altering the number of copies of RNA that are transcribed, to the temporal control of when the gene is ...