Ialungo_Unit7Lab.docx - Name Nicholas Ialungo Course...

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Name: Nicholas Ialungo Course section number:Section 12G Spring 2020 Unit 7: Meiosis Pipe Cleaner ActivityFinal Report: Please extract the final report and save it as Lastname_Unit7labs.docx. Submit the final reportto the course Assignment Box. Remember to type your name and your course section numberin the header of the document.PART 1: LAB PHOTOS1.Attach photos of your completed ‘Mitosis Pipe Cleaner Images and Descriptions’ pages(please submit them in order). Make sure each photo has handwritten on it somewhere clearly visible: your name, course number and section.Meiosis Pipe Cleaner Imagesand Descriptions: InterphaseMeiosis is preceded by an interphase consisting of the G1, S, and G2 phases, which are nearly identical to the phases preceding mitosis. The G1 phase is the first phase of interphase and is focused on cell growth. In the S phase, the DNA of the chromosomes is replicated. Finally, in the G2 phase, the cell undergoes the final preparations for meiosis. During DNA duplication of the S phase, each chromosome becomes composed of two identical copies (called sisterchromatids) that are held together at the centromere until they are pulled apart during meiosis II. In an animal cell, thecentrosomes that organize the microtubules of the meiotic spindle alsoreplicate. This prepares the cell for the first meioticphase.Prophase 1Early in Prophase 1 the chromosomes can be seen clearly microscopically. As the nuclear envelope begins to break down, proteinsassociated with homologous chromosomes bring the pair close to each other. The tight pairing of these chromosomes is called synapsis. An exchange of chromosome segments between non-sister homologous chromatids occurs and is called crossing over. At the end of Prophase 1, the pairs are held together only at chiasmata and are called Tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. The crossover events are the first source of genetic variation produced by meiosis. A single crossover event between non-sister chromatids leads to a reciprocal exchange of equivalent DNA between a maternal chromosome and a paternal chromosome. The recombinant sister chromatid has a combination of maternal and paternal genes that did not exist before the crossover.

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