Ap Biology Lab Report 4 Essays

Ap Biology Lab Report 4 Essays Ap Biology Lab Report 4 Paper Ap Biology Lab Report 4 Paper Introduction 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. Results 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 cells 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. . 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 cell in metaphase E) Nucleolus disappears in prophase 4. The three sub phases of interphase are the G1 phase, S phase, and the G2 phase. I n the G1 phase, cell synthesizes proteins and produces cytoplasmic organelles. In the S phase, DNA synthesis occurs, and in the G2 phase, the cell beings forming the spindle. 5. Both prokaryotic cell division and eukaryotic cell division replicate their DNA and use the process of cytokinesis. Activity B: Estimating the Relative Lengths of Mitotic Phases Table 1: Group Count | Number of Cells| | Field 1| Field 2| Field 3| Total 1-3| Interphase| 52| 46| 57| 155| Prophase| 22| 25| 29| 76| Metaphase| 16| 11| 9| 36| Anaphase| 5| 8| 5| 18| Telophase| 14| 10| 8| 32| | Total| 317| Table 2: Class Data Class Totals| Decimal Fraction of Total Count| Estimated Time Spent in Phase| Interphase| 582| . 46| 13968| Prophase| 305| . 24| 7320| Metaphase| 148| . 12| 3552| Anaphase| 65| . 05| 1560| Telophase| 171| . 13| 4104| Total Cells Counted| 1271| | Analysis of Results, Activity B: Estimating the Relative Lengths of Mitotic Phases Pie Graph 2. Stages of Mitosis Ranked 1) Interphase 2) Prophase 3) Metaphase 4) Anaphase 5) Telophase 3. Some phases of mitosis are longer than othe rs because each phase has a different task, and some of the tasks of the phases are harder than others. For example, interphase takes longer than other phases because the nuclear envelope fragments and the microtubules attach to the chromosomes. Telophase takes the least amount of time because chromosomes only go to opposite ends of the cell and a nuclear membrane forms. Activity C: Simulating Meiosis Analysis of Results, Activity C: Simulating Meiosis 1. Sixteen combinations of the two chromosomes are possible. 2. Number of chromosome combinations= 3. There are possible combinations of chromosomes for human gametes. 4. There are possible combinations of chromosomes for the offspring. 5. The relationship of meiosis to variation in populations is that genes are able to move themselves and combine with different sets of genes that aren’t present in the parent. This causes a higher chance of survival. 6. Three ways that meiosis differs from mitosis are that meiosis occurs in reproductive cells, while mitosis occurs in somatic cells. In meiosis, a mitotic mother cell is always diploid, while in mitosis a mother cell can be haploid or diploid. In meiosis, two divisions of the mother cell causes four meiotic cells, while in mitosis, a single division of the mother cell causes two daughter cells. Activity D: Crossing-Over and Map Units Analysis Results, Activity D: Crossing-Over and Map Units Table 3 | No. of MI Asci (4:4)| No. of MII Asci (2:4:2 or 2:2:2:2)| Total Asci| %MII Asci (No. of MII/Total)| Gene-to Centromere Distance (%MI/2)| Group Data| 45| 65| 110| 59%| 29. 5 (30)| 1. Crossing-over increases genetic variation because when the chromatids exchange sections with each other, they get new combinations of alleles that their parents had, which causes more chromatids. . I would expect to find more genetic variation in the population of species B because it’s undergoing sexual reproduction. In sexual reproduction there is more changeability because the new generation has many combinations of the genes of the two parent organisms. 3. I would conclude that there was no occurrence of recombination since the MI Asci w ould be a 4:4 ratio. Discussion My results proved my hypothesis. This is so because by looking through the microscope it was possible to view the stages of mitosis in the onion root tip and the whitefish blastula. The stages of mitosis that were visible were prophase, anaphase, telophase, interphase, and metaphase. The time spent in each phase was also figured out. Interphase was the phase that the cell spends most of its life in. Telophase was the shortest phase. We stimulated the stages of meiosis using red and yellow magnetic beads. Crossing-over in Sordaria was observed by looking at photos. Afterwards, the map units were determined. We discovered that the distance of the gene relative to the centromere in the Sordaria was fifty-nine map units.