Interphase

Interphase: the stage in the life cycle of a cell where the cell grows and DNA is replicated sister chromatid: either of the two identical strands of a chromosome (DNA material) that separate during mitosis. During interphase, the cell undergoes normal growth processes while also preparing for cell division. In order for a cell to move from interphase into the mitotic phase, many internal and external conditions must be met. The three stages of interphase are called G1, S, and G2 . G1 Phase (First Gap) The first stage of interphase is called the G1 phase (first gap) because, from a microscopic aspect, little change is visible. However, during the G1 stage, the cell is quite active at the biochemical level. The cell grows and accumulates the building blocks of chromosomal DNA and the associated proteins as well as sufficient energy reserves to complete the task of replicating each chromosome in the nucleus. S Phase (Synthesis of DNA) The synthesis phase of interphase takes the longest because of the complexity of the genetic material being duplicated. Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase, DNA replication results in the formation of identical pairs of DNA molecules, sister chromatids, that are firmly attached to the centromeric region. The centrosome is duplicated during the S phase. The two centrosomes will give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis. At the center of each animal cell, the centrosomes of animal cells are associated with a pair of rod-like objects, the centrioles, which are at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of other eukaryotic species, such as plants and most fungi. G2 Phase (Second Gap) In the G2 phase, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase. There may be additional cell growth during G2. The final preparations for the mitotic phase must be completed before the cell is able to enter the first stage of mitosis. Problems: Which of the following events occurs during interphase of the cell cycle? A) condensation of the chromosomes B) separation of the spindle poles C) spindle formation D) replication of the DNA Which of the following processes occurs is unique to prokaryotes (i.e., doesn’t happen in eukaryotes)? A) translation in the absence of a ribosome B) transcription and translation occur simultaneously C) post-transcriptional splicing D) gene splicing #Interphase #Chromatid #Dna #Centrioles #mitoticSpindle #cellBiology #cellLiveCycle