Biology Unit 2: Cell Cycle Mitosis Lab Name: ___________________________ Period: _____ Purpose: In this lab, you will be observing plant cells (onion) and animal cells (whitefish blastula) in the various stages of mitosis. Materials: Microscope Prepared slides of Allium (onion) root tip and whitefish blastula Procedure: 1. Review the visible characteristics of each stage of mitosis. Prophase The chromatin appears as a mass of thick threads. These threads are the replicated chromosomes, which have coiled up and shortened. Each chromosome (x‐shaped DNA) now consists of a pair of identical pieces of DNA. In late prophase, the nucleus cannot be seen, but the chromosomes are distinctly visible in the central region of the cell. Metaphase In metaphase, the chromosomes line up in the middle of the cell. A mass of fibers called a spindle has formed between either end of the cell and the mass of chromosomes. A spindle fiber attaches to each chromosome. Anaphase The chromosomes split and move towards opposite sides of the cell pulled by the spindle fibers. Telophase In this stage, the chromosomes have formed distinctive clumps at each pole. A new nucleus forms around each clump of chromosomes, which uncoil and return to the chromatin network seen in interphase. The new cell walls and cell membrane grow to form the two new, identical daughter cells. Biology Unit 2: Cell Cycle Mitosis Lab Name: ___________________________ Period: _____ 2. Obtain a prepared slide of an Allium root tip. These slides were prepared by thinly slicing the root tip and staining it with a substance which darkens the DNA. 3. Observe the root section under scanning (4x) and low (10X) power. Focus on the apical meristem of the onion root tip. This is the area just behind the root cap. Examine the picture which shows the root cap and apical meristem. 4. Switch to high power. Locate a cell in each stage of mitosis and draw what you see in the data table. Apical Meristem
5. Examine the pictures of whitefish blastula. Identify and draw cells in the various stages of the cell cycle. Root Tip
Data Table: Please create your drawings below. Include as much detail as possible! 1. Prophase Onion White Fish The first sign of division occurs in prophase. Here the replicated chromosomes joined by a centromere begin to coil and thicken. In late prophase the nuclear membrane and nucleoli disappears. The spindle apparatus appears in the cytoplasm. Biology Unit 2: Cell Cycle Mitosis Lab 2. Metaphase Onion Name: ___________________________ Period: _____ White Fish At metaphase, the chromosomes have moved to the center of the cell, moved by the spindle fibers. the centromeres are attached to the spindle fibers 3. Anaphase Onion White Fish At the beginning of anaphase, the chromosomes are separated and moved , by the spindle fibres to the poles of the cell. 4. Telophase Onion White Fish During telophase the nuclear membrane reforms the spindle fibres disappear. Cytokinesis occurs dividing the cell in two daughter cells.