Answer:
Statement 1: Homologous chromosomes line up at the equator in pairs.
Name of Phase: Metaphase 1
Sequence: 3
Statement 2: The cell replicates its chromosomes
Name of Phase: S-Phase, Interphase
Sequence: 1
Statement 3: Homologous chromosomes separate and move to opposite poles of the cell
Name of Phase: Anaphase 1
Sequence: 4
Statement 4: Spindle forms, DNA coils up in homologous chromosomes come together in a tetrad; crossing over may occur.
Name of Phase: Prophase 1
Sequence: 2
Statement 5: Events occur in reverse order of prophase 1
Name of Phase: Telophase 1
Sequence: 5
Explanation:
Following is a summary of the events of meiosis:
1. Interphase:
Prepares the cell for division. Duplication of DNA, duplication of centrioles occurs and the cell grows in size. At this stage the cell is diploid (2n).
2. Prophase 1:
First stage of Meiosis 1.The centrioles move to the poles of the cell, the nuclear membrane disintegrates, homologous chromosomes pair up (in the form of tetrad), form a chiasmata and then exchange segments of chromosomes with each other. This process is called crossing over.
3. Metaphase 1:
Involves the arrangement of the crossed over, homologous chromosomes on the metaphase plate which is sort of like a web of spindle fibers that originates from the centrioles.
4. Anaphase 1:
The tetrads arranged on the metaphase plate are pulled apart by the spindle fibers. This is the result of tension that build up in the spindle fibers as they grow towards opposite poles.
5. Telophase 1:
The last stage of meiosis 1. Involves the arrival of the chromosomes at the poles, the nuclear membrane starts to form and the chromosomes start decondensing. Telophase 1 yields 2 daughter cells with half the number of chromosomes as that in the parent cell.
Meiosis 2:
Meiosis 2 is exactly similar to mitosis. The only difference is that the haploid cells entering meiosis 2 do not duplicate their DNA. Meiosis 2 just involves the separation of the sister chromatids of homologous chromosomes.
- As mentioned above, interphase does not occur before meiosis 2.
- Prophase 2 involves the disintegration of nuclear envelope, centrosomes start moving to the poles.
- Metaphase 2 arranges the chromosomes on metaphase plate.
- Anaphase 2 separates the sister chromatids from the chromosomes.
- Telophase 2 develops the nuclear envelope and separates the nuclei of the daughter cells into 2. Nuclear division id followed by cytokinesis (division of cytoplasm). Telophase 2 result sin 4 haploid daughter cells with one chromatid from each chromosome.
