Bio-Pac 04: Objective 01-02

Question 1

Objective 1. List and describe, in sequence, the four stages of the cell cycle.

Answer 1

There are four stages in the cell cycle. The first is the growth stage (G1), then the synthesis stage (S), the 2nd period of growth (G2) and finally mitosis. In the first period of growth the chromosomes will condense, there will be an increase in the number of mitochondria, ribosomes, enzymes, and other cytoplasmic molecules, synthesis of RNA and proteins will occur, and replication of centrioles (animal cells only) will occur. In this sage there is a certain point (Restriction point(R)) that if a cell passes, the cell must continue the remaining stages of the cycle. The second stage of the cycle, there is still an increase in number of ribosomes, mitochondria, enzymes, and other cytoplasmic reticulum, synthesis of RNA and proteins, replication of centrioles (only in animal cells) as well as DNA REPLICATION (from uncondensed chromatin), and Histone synthesis. The third stage, 2nd period of growth, is a preparation stage for cell division. In this stage there is still an increase in the number of ribosomes, mitochondria, enzymes, and other cytoplasmic molecules, synthesis of RNA and proteins, and replication of centrioles, as well as disaggregation (separate into parts) of cytoskeleton, centrioles duplication is completed, and aggregation (forming) of microtubular proteins (synthesized during G1 and S). The first three stages all together are called the interphase. The fourth stage is where there is a visible condensation of chromosomes meaning that it is the beginning of mitosis, microtubules and mircofilaments direct the movement of chromosomes, and the cell divides. This stage has four phases which will be explained in the next objective. The four stages are prophase, metaphase, anaphase, and telophase. After these four phases there is cytokinesis which marks the end of cell division, there is a dividing of cytoplasm, and now you have two separate cells instead of one.

Question 2

Objective 2. Diagram and label the four phases a cell goes through during cell division including each of the following when applicable: nucleus, nucleolus, chromatin, nuclear membrane, centrioles, spindle fibers, equator, poles, sister chromatids, centromere, and cleavage furrow.

Answer 2

Prophase

Metaphase

Anaphase

Telophase