Ap Biology Lab Report 4

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This study was performed in order to gain more knowledge on mitosis and meiosis. This lab was done by observing mitosis in plant and animal cells, comparing the relative lengths of the stages of mitosis in onion root tip cells, stimulating the stages of meiosis, observing evidence of crossing-over in meiosis using Sordaria fimicola, and estimating the distance of a gene locus from its centromere. Mitosis is the scientific term for nuclear cell division, where the nucleus of the cell divides, resulting in two sets of identical chromosomes. Mitosis is accompanied by cytokinesis in which the end result is two completely separate cells called daughter cells. There are four phases of mitosis: prophase, metaphase, anaphase and telophase. Meiosis is a two-part cell division process in organisms that sexually reproduce. Meiosis produces gametes with one half the number of chromosomes as the parent cell. There are two stages of meiosis: meiosis I and meiosis II. At the end of the meiotic process, four daughter cells are produced. Each of the resulting daughter cells has one half of the number of chromosomes as the parent cell. Mitosis was studied first in this lab. The phases of onion root tips were observed under a microscope. The crossing-over of chromosomes in meiosis was observed by viewing photos. Hypothesis

If looking under a 400 power microscope, than it is possible to observe mitosis occurring in whitefish blastula and onion root tips. If crossing-over occurs in meiosis, than the genes do not segregate until meiosis II. Materials and Methods

All materials and methods followed based off of lab manual.

Activity A: Observing Mitosis
Interphase Cells

Plant Cell Animal Cell

Prophase Cells
The cellular organelles doubled in number, the DNA replicated, and protein synthesis occurred. The chromosomes are not visible and the DNA appears as uncoiled chromatin. Prophase

Plant Cell Animal Cell The chromatin condensed and the chromosomes became visible. The nucleolus disappeared, and the spindle forms and attaches to the centromeres of the chromosomes. Early and late prophase can be seen. In late prophase, the chromatin has condensed into chromosomes, the nucleolus is gone, and the nuclear envelope has been removed.

Metaphase Cells
Plant Cell Animal Cell

The nuclear membrane fragmentation is complete and the duplicated chromosomes lined up along the cell's equator. Anaphase Cells
Plant Cell Animal Cell

Diploid sets of daughter chromosomes separated and were pushed and pulled toward opposite poles of the cell. This was accomplished by the polymerization and depolymerization of the microtubules that helped to form the mitotic spindle. Telophase Cells

Plant Cell Animal Cell

The nuclear membrane and nucleoli reformed, cytokinesis is almost done, and the chromosomes uncoiled to chromatin. Daughter Cells
Plant Cell Animal Cell

The daughter cells formed and constructed a new dividing cell wall between them. Each daughter cell received a copy of the genome of its parent’s cell. Analysis of Results, Activity A: Observing Mitosis

1. I can infer that the two cells came from the cell a long time ago because they have similar organelles. 2. Two ways that mitosis differs in the cells of animals and higher plants is in cytokinesis and right before prophase. In plant cells, there is a pre-prophase right before prophase takes place. 3. A) Nuclear envelope disappears in prophase; nuclear envelope reappears in telophase B) Mitotic spindle forms in prophase; mitotic spindle disappears in telophase C) Chromatin condenses into chromosomes in prophase; chromosomes unwind to form chromatin in telophase D) Centrosomes are at opposite ends of the...
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