How does meisosis differ in plant and animal cells?
Meiosis is a type of cell division which reduces the chromosomes number. The processses are quite
the same in plants and animals. However, in animals, it reults into the formation of gametes which
is a reproductive or sex cell. On the other hand, in plants, it forms spores which further grow into
gametophyte.
Science Teacher Guide
Sexual reproduction. During reproduction, when the sperm and egg unite to form a single cell,
the number of chromosomes is restored in the offspring.
Meiosis begins with a parent cell that is diploid, meaning it has two copies of each chromosome.
The parent cell undergoes one round of DNA replication followed by two separate cycles of
nuclear division. The process results in four daughter cells that are haploid, which means they
contain half the number of chromosomes of the diploid parent cell.
Meiosis has both similarities to and differences from mitosis, which is a cell division process in
which a parent cell produces two identical daughter cells. Meiosis begins following one round
of DNA replication in cells in the male or female sex organs. The process is split into meiosis
I and meiosis II, and both meiotic divisions have multiple phases. Meiosis I is a type of cell
division unique to germ cells, while meiosis II is similar to mitosis.
Meiosis I, the first meiotic division, begins with prophase I. During prophase I, the complex
of DNA and protein known as chromatin condenses to form chromosomes. The pairs of
replicated chromosomes are known as sister chromatids, and they remain joined at a central
point called the centromere. A large structure called the meiotic spindle also forms from
long proteins called microtubules on each side, or pole, of the cell. Between prophase I and
metaphase I, the pairs of homologous chromosome form tetrads. Within the tetrad, any pair
of chromatid arms can overlap and fuse in a process called crossing-over or recombination.
Recombination is a process that breaks, recombines and rejoins sections of DNA to produce
new combinations of genes. In metaphase I, the homologous pairs of chromosomes align on
either side of the equatorial plate. Then, in anaphase I, the spindle fibers contract and pull the
homologous pairs, each with two chromatids, away from each other and toward each pole of
the cell. During telophase I, the chromosomes are enclosed in nuclei.
The cell now undergoes a process called cytokinesis that divides the cytoplasm of the original
cell into two daughter cells. Each daughter cell is haploid and has only one set of chromosomes,
or half the total number of chromosomes of the original cell.
Meiosis II is a mitotic division of each of the haploid cells produced in meiosis I. During prophase
II, the chromosomes condense, and a new set of spindle fibers forms. The chromosomes begin
moving toward the equator of the cell. During metaphase II, the centromeres of the paired
chromatids align along the equatorial plate in both cells. Then in anaphase II, the chromosomes
separate at the centromeres. The spindle fibers pull the separated chromosomes toward
each pole of the cell. Finally, during telophase II, the chromosomes are enclosed in nuclear
membranes. Cytokinesis follows, dividing the cytoplasm of the two cells. At the conclusion of
meiosis, there are four haploid daughter cells that go on to develop into either sperm or egg
cells.
note: write these notes in summary form
1 answer
Summary of Meiosis in Plant and Animal Cells
General Overview:
Meiosis is a type of cell division that reduces the chromosome number, resulting in haploid cells.
The process is similar in both plants and animals but leads to different outcomes:
In animals, meiosis produces gametes (sperm and eggs).
In plants, it forms spores that develop into gametophytes.
Meiosis Process:
Diploid Parent Cell: Starts as a diploid cell (two sets of chromosomes).
DNA Replication: One round of DNA replication occurs.
Two Meiotic Divisions: Meiosis consists of two main phases—meiosis I and meiosis II.
Meiosis I:
Prophase I: Chromatin condenses into chromosomes; homologous chromosome pairs form tetrads. Crossing-over occurs, leading to genetic recombination.
Metaphase I: Homologous pairs align at the equatorial plate.
Anaphase I: Spindle fibers pull homologous chromosomes to opposite poles.
Telophase I and Cytokinesis: Nuclear membranes form around separated sets; the cell divides into two haploid daughter cells.
Meiosis II:
Prophase II: Chromosomes condense and spindle fibers reform.
Metaphase II: Chromatids align at the equatorial plate.
Anaphase II: Centromeres split, and chromatids move to opposite poles.
Telophase II and Cytokinesis: Nuclear membranes reform; the two haploid cells from meiosis I each divide, resulting in a total of four haploid daughter cells.
Conclusion: Meiosis results in four haploid daughter cells, which in animals develop into gametes and in plants develop into spores that produce gametophytes.
