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Oct 21, 2023 · Meiosis Definition, Diagram, Steps, and Function. Meiosis produces haploid gametes from a diploid cell. DNA replicates once, but the cells divide twice. In biology, meiosis is the process where a cell replicates DNA once but divides twice, producing four cells that have half the genetic information of the original cell.
The cell cycle is an orderly sequence of events. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages. In eukaryotes, the cell cycle consists of a long preparatory period, called interphase. Interphase is divided into G 1, S, and G 2 phases.
- Charles Molnar, Jane Gair
- 2015
During meiosis in humans, 1 diploid cell (with 46 chromosomes or 23 pairs) undergoes 2 cycles of cell division but only 1 round of DNA replication. The result is 4 haploid daughter cells known as gametes or egg and sperm cells (each with 23 chromosomes – 1 from each pair in the diploid cell).
The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division that produce two genetically identical cells.
- Regulation at Internal Checkpoints
- The G1 Checkpoint
- The G2 Checkpoint
- The M Checkpoint
- Regulator Molecules of The Cell Cycle
- Positive Regulation of The Cell Cycle
It is essential that the daughter cells produced be exact duplicates of the parent cell. Mistakes in the duplication or distribution of the chromosomes lead to mutations that may be passed forward to every new cell produced from an abnormal cell. To prevent a compromised cell from continuing to divide, there are internal control mechanisms that ope...
The G1 checkpoint determines whether all conditions are favorable for cell division to proceed. The G1 checkpoint, also called the restriction point (in yeast), is a point at which the cell irreversibly commits to the cell division process. External influences, such as growth factors, play a large role in carrying the cell past the G1 checkpoint. I...
The G2 checkpoint bars entry into the mitotic phase if certain conditions are not met. As at the G1 checkpoint, cell size and protein reserves are assessed. However, the most important role of the G2 checkpoint is to ensure that all of the chromosomes have been replicated and that the replicated DNA is not damaged. If the checkpoint mechanisms dete...
The M checkpoint occurs near the end of the metaphase stage of karyokinesis. The M checkpoint is also known as the spindle checkpoint, because it determines whether all the sister chromatids are correctly attached to the spindle microtubules. Because the separation of the sister chromatids during anaphase is an irreversible step, the cycle will not...
In addition to the internally controlled checkpoints, there are two groups of intracellular molecules that regulate the cell cycle. These regulatory molecules either promote progress of the cell to the next phase (positive regulation) or halt the cycle (negative regulation). Regulator molecules may act individually, or they can influence the activi...
Two groups of proteins, called cyclins and cyclin-dependent kinases (Cdks), are responsible for the progress of the cell through the various checkpoints. The levels of the four cyclin proteins fluctuate throughout the cell cycle in a predictable pattern (Figure 10.11). Increases in the concentration of cyclin proteins are triggered by both external...
Chapter 7: Introduction to the Cellular Basis of Inheritance. 7.2 Meiosis. Learning Objectives. By the end of this section, you will be able to: Describe the behavior of chromosomes during meiosis. Describe cellular events during meiosis. Explain the differences between meiosis and mitosis.
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The cell cycle is an orderly sequence of events. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages. In eukaryotes, the cell cycle consists of a long preparatory period, called interphase. Interphase is divided into G 1, S, and G 2 phases.
