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Anatomy

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Histology

Question
43 out of 59
 

The correct sequence of cell cycle is (LQ)



A G0-G1-S-G2-M
B G0-G1-G2-S-M

C G0-M-G2-S-G1
D G0-G1-S-M-G2

Ans. A

G0-G1-S-G2-M

 The cell cycle, or cell-division cycle (CDC), is the series of events in a eukaryotic cell between one cell division and the next.

 Thus, it is the process by which a single-cell fertilized egg develops into a mature organism (cleavage) and the process by which hair, skin, blood cells, and some internal organs are renewed.

 A specialized form of cell division is responsible for cellular differentiation during embryogenesis and morphogenesis, as well as for the maintenance of stem cells during adult life.

 The cell cycle consists of four distinct phases: G1 phase, S phase, G2 phase (collectively known as interphase) and M phase.

Interphase is a phase of the cell cycle, defined only by the absence of cell division.

 During interphase, the cell obtains nutrients, and duplicates its chromosomes.

 Most of the cells spend most of their time in interphase. For example, human skin cells, which divide about once a day, spend roughly 22 hours in interphase.

 Cells during interphase may or may not be growing. Some cells, such as nerve cells, can stay in interphase for decades. The cell grows and replicates its DNA and centrioles.

 There are 3 parts of interphase: G1 (growth 1 in which the cell creates organelles and begins metabolism), S phase (DNA synthesis in which the chromosomes of the cell are copied) and G2 (growth 2 in which the cell grows in preparation for cell division)

 M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's chromosomes are divided between the two daughter cells, and cytokinesis, in which the cell's cytoplasm physically divides.

 Cells that have temporarily or reversibly stopped dividing are said to have entered a state of quiescence called G0 phase, while cells that have permanently stopped dividing due to age or accumulated DNA damage are said to be senescent.

 The molecular events that control the cell cycle are ordered and directional; that is, each process occurs in a sequential fashion and it is impossible to "reverse" the cycle.

 There are two key classes of regulatory molecules that determine a cell's progress through the cell cycle: cyclin(s) and cyclin-dependent kinases.

Histology Flashcard List

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