Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous...
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Transcript of Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous...
![Page 1: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/1.jpg)
Chromosome structure
![Page 2: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/2.jpg)
Chromosomes
Example - an organism is 2n = 4.
Chromosomes 1 & 2 are homologous chromosomes
Chromosomes 3 & 4 are homologous chromosomes
Chromosomes 1 & 3 came from the mother
Chromosomes 2 & 4 came from the father
![Page 3: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/3.jpg)
Life cycle
![Page 4: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/4.jpg)
Cell division - Mitosis
The stages of the cell cycle can be broken down into six stages: Interphase, Prophase, Metaphase, Anaphase, Telophase
• Interphase is the "resting" or non-mitotic portion of the cell cycle.
• DNA is replicated during the Interphase
![Page 5: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/5.jpg)
Prophase - the first stage of mitosis.
• The chromosomes condense and become visible
• The nuclear membrane dissolves
![Page 6: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/6.jpg)
Metaphase
The chromosomes line up in the middle of the cell ("the equator")
![Page 7: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/7.jpg)
Anaphase
• Spindles begin to shorten.
• This exerts a force on the sister chromatids that pulls them apart.
• This ensures that each daughter cell gets identical sets of chromosomes
![Page 8: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/8.jpg)
Telophase
The chromosomes decondense
The nuclear envelope forms
Cytokinesis reaches completion, creating two daughter cells
![Page 9: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/9.jpg)
Meiosis
Special Type of Cell Division That Occurs in Sexually Reproducing Organisms
• Meiosis reduces the chromosome number by half, enabling sexual recombination to occur.
• Meiosis of diploid cells produces haploid daughter cells, which may function as gametes.
• Gametes undergo fertilization, restoring the diploid number of chromosomes in the zygote
![Page 10: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/10.jpg)
Meiosis• Meiosis and fertilization introduce genetic variation in
three ways:
1. Crossing over between homologous chromosomes at prophase I.
2. Independent assortment of homologous pairs at metaphase I: Each homologous pair can orient in either of two ways at the plane of cell division.
3. Random chance fertilization between any one female gamete with any other male gamete.
![Page 11: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/11.jpg)
Meiosis• The stages of meiosis can be broken down into two main
stages, Meiosis I and Meiosis II
• Meiosis I can be broken down into four substages: Prophase I, Metaphase I, Anaphase I and Telophase I
• Meiosis II can be broken down into four substages: Prophase II, Metaphase II, Anaphase II and Telophase II
![Page 12: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/12.jpg)
Prophase IThe chromosomes condense and become visible
The nuclear membrane begins to dissolve
The homologs pair up, forming a tetrad
Each tetrad is comprised of four chromatids - the two homologs, each with their sister chromatid
Homologous chromosomes will swap genetic material in a process known as crossing over
![Page 13: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/13.jpg)
Crossing Over
![Page 14: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/14.jpg)
Metaphase I
The tetrads line up along the cell equator
![Page 15: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/15.jpg)
Anaphase I
• The centromeres break and homologous chromosomes separate (note that the sister chromatids are still attached)
• Cytokinesis begins
![Page 16: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/16.jpg)
Telophase I
• The chromosomes may decondense
• Cytokinesis reaches completion, creating two haploid daughter cells
![Page 17: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/17.jpg)
Prophase II
The nuclear membrane dissolves
![Page 18: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/18.jpg)
Metaphase II
The sister chromatids line up along the cell equator
![Page 19: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/19.jpg)
Anaphase II
• The centromeres break and sister chromatids separate
• Cytokinesis begins
![Page 20: Chromosome structure. Chromosomes Example - an organism is 2n = 4. Chromosomes 1 & 2 are homologous chromosomes Chromosomes 3 & 4 are homologous chromosomes.](https://reader036.fdocuments.us/reader036/viewer/2022062422/56649f315503460f94c4c65b/html5/thumbnails/20.jpg)
Telophase II
• Cytokinesis reaches completion, creating four haploid daughter cells