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Cell Cycle Reading Guide
The Cell cycle
1.What is meant by the cell cycle or cell division cycle? ** Series of events that take place in a eukaryotic cell between its formation and the
moment it replicates itself.
- In what type of cells --- prokaryotes or eukaryotes --- does the cell cycle occur?
- Name the 2 main PHASES of the cell cycle. Interphase & Mitotic Phase
- Mitotic phase is in between the times when a cell is dividing.
- What is occurring in a cell during interphase? The cell is forming and carries on with its normal metabolic functions.
- What is happening during the mitosis phase? The cell is replicating itself
- A fertilized egg develops into a mature organism during the cell cycle.
- Name three things that form during the cycle. Hair, skin, blood cells
Interphase
- What process NEVER occurs in interphase? Division
10.Cells obtain nutrients and duplicate or copy their chromatids or genetic material during interphase.
- Where are chromatids found in a cell? Nucleus
- Chromatids are made of a molecule called chromatin.
- Label this chromosome.
- Chromosome
- centromere
- short arm (chromatid)
- long arm chromatid
14.In what PHASE do most cells spend the majority of their lifetime? interphase
- How often do human skin cells divide each day? Once a day
- How many hours per day is a human skin cell in interphase? 22
- What type of cell may spend decades in interphase instead of dividing? nerve cells
- Name the 3 stages in interphase. G1, S, G
- What does G 1 stand for and what occurs in this stage? Growth- creates cell organelles & begins metabolism
- What does S stand for and what occurs in this stage? Synthesis- chromosomes of the cell are copied
- What happens during the S phase? Each chromosome is copied.
- Each chromosome originally is made of how many DNA molecules and how does this molecule appear in the chromosome? One coiled double helix - chromatid
- At the end of S phase each chromosome has how many coiled DNA molecules? 2 identical double helices
36.What structure holds the duplicated chromosomes together and is also copied
during the S phase? centrosomes
37.What is the final and shortest phase of interphase? G
- About how long would a typical cell be in the G 2 phase? Four to five hours
- How is the cell prepared for mitosis during the G 2 phase? The cell grows
- What follows the G2 phase? Mitosis
- What part of the cell is actually dividing in mitosis? Nucleus and nuclear
material
- What is another name for mitosis? Karyokinesis
Cell Cycle and Mitosis
THE CELL CYCLE
The cell cycle , or cell-division cycle , is the series of events that take place in a eukaryotic cell between its formation and the moment it replicates itself.
These events can be divided in two main parts: interphase (in between divisions
phase grouping G 1 phase, S phase, G 2 phase ), during which the cell is forming and carries on with its normal metabolic functions; the mitotic phase (M mitosis), during which the cell is replicating itself. Thus, cell-division cycle is an essential process by which a single-cell fertilized egg develops into a mature organism and the process by which hair, skin, blood cells, and some internal organs are formed.
INTERPHASE
Interphase is a phase of the cell cycle, defined only by the absence of cell division. During interphase, the cell obtains nutrients , and duplicates (copies) its chromatids (genetic material). The genetic material or chromatids are located in the nucleus of the cell and are made of the molecule DNA.
Chromatids are connected by the centromere and have a LONG AND SHORT ARM.
Most eukaryotic 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. About 90 percent of cells are in interphase. Some cells, such as nerve cells, can stay in interphase for decades. There are 3 parts of interphase: G 1 (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 G 2 (growth 2 in which the cell grows in preparation for cell division). Find the cell cycle drawing on this worksheet and draw an additional line in red around those parts of the cell cycle diagram that are included in interphase.
Sometimes the cells exit the cell cycle (usually from G 1 phase) and enter the G 0 phase. In the G 0 phase, cells are alive and metabolically active , but do not divide. In this phase cells do not copy their DNA and do not prepare for cell division. Many cells in the human body, including those in heart muscle , eyes, and brain are in the G 0 phase. If these cells are damaged they cannot be replaced. Again find the cell
