本期內(nèi)容是實驗七-減數(shù)分裂的實驗手冊，實驗模擬請看下一期。本部分內(nèi)容來自 University of California, Berkeley - UC Berkeley Extension, 虛擬實驗的內(nèi)容來自 Labster. 本部分內(nèi)容均不會標記為為原創(chuàng)，但由于是UP主購買的課程，因此不接受非授權的轉載，謝謝您的理解。

每一個生物基礎實驗均會分為三部分：第一部分為實驗的生物理論；第二部分為實驗的指導手冊；第三部分為 Labster 的虛擬實驗模擬。第一部分的基本信息由 Ying Liu, Ph.D. 提供，第二部分的實驗手冊來自 Labster, 第三部分的實驗模擬過程均由UP主操作。

Virtual Lab Manual - Meiosis: Understand how traits are inherited

Synopsis

Join an IVF lab to help Martin and Charlotte have a baby. In this simulation, you will learn how traits are inherited and how meiosis contributes to genetic diversity in the population. You will use microscopy to study the process of cell division. You will discover the key differences beTween meiosis and mitosis and find out how these processes contribute to forming, growing and repairing the human body.

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Meet Martin and Charlotte in the clinic

Meet Martin and Charlotte as they have an appointment to discuss IVF treatment and then join the clinic’s lab to understand meiosis before assisting in the IVF process. Learn how gametes are formed and how they fuse in fertilization.

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Use microscopy to study meiosis

Prepare a sample of a lily anther for microscopy and study the phases of meiosis. Then compare meiosis and mitosis and learn how each of these processes contributes to human reproduction. You will complete interactive diagrams of both meiosis and mitosis to create a visual overview for yourself.

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Follow the IVF process

Once you fully understand how gametes are formed through meiosis, you will follow the process of fertilization. Screen the resulting embryos to see both sets of parental chromosomes combine to a full set of pairs. Will you be able to help Martin and Charlotte have a healthy baby?

Learning Objectives

At the end of this simulation, you will be able to…

●?Outline how traits are inherited

●?Use the microscope to observe the phases of meiosis and understand their main characteristics

●?Compare phases and outcomes of mitosis and meiosis

●?Evaluate how meiosis and mitosis build and maintain a complex organisM

●?Understand the basics of assisted reproduction technology

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Techniques in Lab

●?Sample preparation

●?Microscopy

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Theory

Cell Reproduction

Mitosis?and meiosis?are both involved in reproduction. However, they have different roles. Asexual reproduction?only involves mitosis, while sexual reproduction?involves both mitosis and meiosis.

●?Somatic cells

●?Gametes

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Meiosis

Meiosis, unlike mitosis, creates daughter cells that have half as many chromosomes as the parent cell (Figure below).

Meiosis is preceded by an interphase consisting of the G1, S, and G2?phases, which are nearly identical to the preceding phases mitosis. During DNA duplication in the S phase, each chromosome is replicated to produce Two identical copies, called sister chromatids, that are held together at the centromere by cohesin proteins. Cohesin?holds the chromatids together until anaphase II.

Function of meiosis:

●?Reduce the number of chromosomes from diploid to haploid

●?Ensure each daughter cells has a complete set of chromosomes

●?Generate genetic diversity among the daughter cells

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Meiosis consists of Two nuclear divisions, meiosis I?and meiosis II, that reduce the number of chromosomes to the haploid number, in preparation for sexual reproduction. In meiosis I, Two unique events happen:

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●?Synapsis and crossing over. During prophase I, the homolog pairs up and is held by synapsis. Crossing over also happens during prophase I.

●?Homologous pairs at the metaphase plate. During metaphase I, homologous chromosomes come together to pair along their entire length. This pairing doesn’t occur in mitosis.

●?Separation of homolog.?During anaphase I, the homologous chromosome pairs separate, but the individual chromosome, each consisting of Two sister chromatids remain intact.

In meiosis II, the sister chromatids are separated.

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Mitosis and Meiosis Comparison

Two types of cell division serve a different purpose: cell divisions where chromosomes/ DNA are exactly replicated in new cells (mitosis) and reduction division where the number of chromosomes is halved in the new cells (meiosis). Reduction division is essential if genetic information from each parent is to be contributed to the offspring. In both mitosis and meiosis, the chromosomes or chromatids are pulled to opposite poles of the cell by the mitotic spindle composed of microtubules before cytokinesis.

Summary of Differences:?End product of mitosis is 2 daughter cells, whereas meiosis produces 4 daughter cells.

1.?Mitosis forms diploid cells that have the same number of chromosomes as the parent, whereas meiosis forms haploid cells with half the original number of chromosomes.

2.?Mitosis produces somatic cells (all cells except sex cells) while meiosis produces sex cells, ie. egg or sperm cells.

3.?Mitosis includes one round of cell division, while meiosis contains Two rounds of cell division.

4.?Stages of mitosis include interphase, prophase, metaphase, anaphase and telophase. Stages of meiosis include interphase, prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, and telophase II.

5.?In mitosis, homologs do not pair up, whereas in meiosis homologs do pair up.

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Assisted Reproductive Technology

Assisted Reproductive Technology (ART) procedures involve surgically removing eggs from a woman’s ovaries, combining them with sperm in a laboratory, and returning them to the woman’s body or donating them to another woman.

The most commonly used Assisted Reproductive Technology (ART) is in vitro fertilization?(IVF). To test the result of Assisted Reproductive Technology (ART), a preimplantation genetic diagnosis is performed.

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本期內(nèi)容到此結束，感謝閱讀！下一期將進行 Labster 實驗！