Gametophyte- Haploid phase where gametes are produced. Two Phases of Alteration of Generation A multicellular haploid generation alternates with a multicellular diploid generation. Meiosis and Sexual Reproduction. Chapter 10 Meiosis and Sexual Reproduction. Chromosome Numbers: All sexually reproducing organisms have pairs of chromosomes.
Homologous Chromosomes:. Meiosis Is a form of cell division that halves the number of chromosomes when forming specialized reproductive cells gametes. Similar presentations. Upload Log in. My presentations Profile Feedback Log out. Log in. Auth with social network: Registration Forgot your password? Download presentation. Cancel Download. Presentation is loading. Please wait. Copy to clipboard. Presentation on theme: Do you remember… mitosis This chapter deals with making cells that are genetically different through meiosis!
Why is meiosis important?
- Meiosis, Genetic Recombination, and Sexual Reproduction.
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Sexual Reproduction. Amber Tharpe. Homologous Chromosomes: Please wait OK Meiosis Chapter 11 Sec. Meiosis Reduces of chromosomes to half Diploid 2n to haploid 1n.
About project SlidePlayer Terms of Service. Facts In the Cell. Meiosis produces our sex cells or gametes eggs in females and sperm in males. These are divided between the first time the cell divides meiosis I and the second time it divides meiosis II: Meiosis I 1. The DNA in the cell is copied resulting in two identical full sets of chromosomes. Outside of the nucleus are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.
[Meiotic weakness: the first division].
During interphase, microtubules extend from these centrosomes. Prophase I: The copied chromosomes condense into X-shaped structures that can be easily seen under a microscope. Each chromosome is composed of two sister chromatids containing identical genetic information. The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and so on. The pairs of chromosomes may then exchange bits of DNA in a process called recombination or crossing over. At the end of Prophase I the membrane around the nucleus in the cell dissolves away, releasing the chromosomes.
The meiotic spindle, consisting of microtubules and other proteins, extends across the cell between the centrioles. Metaphase I: The chromosome pairs line up next to each other along the centre equator of the cell.
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The centrioles are now at opposites poles of the cell with the meiotic spindles extending from them. The meiotic spindle fibres attach to one chromosome of each pair. Anaphase I: The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to one pole of the cell and the other chromosome to the opposite pole. In meiosis I the sister chromatids stay together. This is different to what happens in mitosis and meiosis II.
Telophase I and cytokinesis: The chromosomes complete their move to the opposite poles of the cell. At each pole of the cell a full set of chromosomes gather together.
Mitosis - Wikipedia
The single cell then pinches in the middle to form two separate daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis.
Meiosis II 6. Prophase II: Now there are two daughter cells, each with 23 chromosomes 23 pairs of chromatids. In each of the two daughter cells the chromosomes condense again into visible X-shaped structures that can be easily seen under a microscope.
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The membrane around the nucleus in each daughter cell dissolves away releasing the chromosomes. The centrioles duplicate. The meiotic spindle forms again. Metaphase II: In each of the two daughter cells the chromosomes pair of sister chromatids line up end-to-end along the equator of the cell. The centrioles are now at opposites poles in each of the daughter cells. Meiotic spindle fibres at each pole of the cell attach to each of the sister chromatids.