Search results
People also ask
What are the two stages of meiosis?
How is meiosis divided?
What happens in meiosis 2?
What is the difference between meiosis 1 & 2?
The four stages of meiosis II are as follows:- Prophase II – It immediately sets off after the cytokinesis when the daughter cells are formed. The chromosomes begin to condense accompanied by the dissolution of the nuclear membrane and the disappearance of the Golgi apparatus and ER complex.
This short video explains the role of meiotic cell division. Reduction division in a cell in which the chromosome number is halved from diploid to haploid. These are sperm and eggs (ova) in...
- What Is meiosis?
- Function of Meiosis
- Phases of Meiosis
- Phases of Meiosis I
- Phases of Meiosis II
- Examples of Meiosis
- Related Biology Terms
- Quiz
Meiosis is the process in eukaryotic, sexually-reproducing animals that reduces the number of chromosomes in a cell before reproduction. Many organisms package these cells into gametes, such as egg and sperm. The gametes can then meet, during reproduction, and fuse to create a new zygote. Because the number of alleles was reduced during meiosis, th...
Meiosis is necessary for many sexually-reproducing animals to ensure the same number of chromosomes in the offspring as in the parents. The act of fertilization includes two cells fusing together to become a new zygote. If the number of alleles of each gene is not reduced to 1 in the gametes that produce the zygote, there will be 4 copies of each g...
Before meiosis, the DNA is replicated, as in mitosis. Meiosis then consists of two cell divisions, known as meiosis I and meiosis II. In the first division, which consists of different phases, the duplicated DNA is separated into daughter cells. In the next division, which immediately follows the first, the two alleles of each gene are separated in...
Prophase I
Prophase I, the first step in meiosis I, is similar to prophase in mitosis in that the chromosomes condense and move towards the middle of the cell. The nuclear envelope degrades, which allows the microtubules originating from the centrioles on either side of the cell to attach to the kinetochores in the centromeres of each chromosome. Unlike in mitosis, the chromosomes pair with their homologous partner. This can be seen in the red and blue chromosomes that pair together in the diagram. This...
Metaphase I
In metaphase I of meiosis I, the homologous pairs of chromosomes line up on the metaphase plate, near the center of the cell. This step is referred to as a reductional division. The homologous chromosomes that contain the two different alleles for each gene are lined up to be separated. As seen in the diagram above, while the chromosomes line up on the metaphase plate with their homologous pair, there is no order upon which side the maternal or paternal chromosomes line up. This process is th...
Anaphase I
Much like anaphase of mitosis, the chromosomes are now pulled towards the centrioles at each side of the cell. However, the centrosomes holding the sister chromatids together do not dissolve in anaphase I of meiosis, meaning that only homologous chromosomes are separated, not sister chromatids.
Prophase II
Prophase II resembles prophase I. The nuclear envelopes disappear and centrioles are formed. Microtubules extend across the cell to connect to the kinetochores of individual chromatids, connected by centromeres. The chromosomes begin to get pulled toward the metaphase plate.
Metaphase II
Now resembling mitosis, the chromosomes line up with their centromeres on the metaphase plate. One sister chromatid is on each side of the metaphase plate. At this stage, the centromeres are still attached by the protein cohesin.
Anaphase II
The sister chromatids separate. They are now called sister chromosomes and are pulled toward the centrioles. This separation marks the final division of the DNA. Unlike the first division, this division is known as an equational division, because each cell ends up with the same quantity of chromosomes as when the division started, but with no copies.
Human Meiosis
Human meiosis occurs in the sex organs. Male testis produce sperm and female ovaries produce eggs. Before these gametes are made, however, the DNA must be reduced. Humans have 23 distinct chromosomes, existing in homologous pairs between maternal and paternal DNA, meaning 46 chromosomes. Before meiosis, the DNA in the cell is replicated, producing 46 chromosomes in 92 sister chromatids. Each pair of sister chromatids has a corresponding (either maternal or paternal) set of sister chromosomes....
Fruit Flies
Fruit flies have 4 pairs of chromosomes or 8 chromosomes in regular cells. Before meiosis takes place, each chromosome is replicated, leaving 8 chromosomes and 16 sister chromatids. Meiosis I takes place, and there are 2 cells, each with only 4 chromosomes. Each chromosome is still made of sister chromatids, and some crossing-over may have occurred during metaphase I. Meiosis II now takes place on those two cells. In total, 4 cells are created, again. However, these cells have 4 chromosomes....
Haploid– Organism with only one copy of each gene in each cell, or gametes with such.Diploid– Two copies of each gene, per cell.PolyploidDominance– Multiple (more than two) copies of each gene per cell.Sister Chromatids– The replicated DNA that exist as a single chromosome until separated in anaphase.1. A cell is going through meiosis. The sister chromatids are lined up on the metaphase plate. What phase of meiosis is this? A. Metaphase I B. Prophase II C.Metaphase II 2. An adult organism has 60 chromosomes or 30 homologous chromosomes. 30 are maternally derived, 30 are paternally derived. How many chromosomes are in each cell after mitosis? A....
Oct 21, 2023 · Meiosis involves two divisions, so it’s typically broken down into meiosis I and meiosis II. Here’s a breakdown of the stages of meiosis and a look at what happens: Meiosis I. Cells enter meiosis from interphase, which is much like interphase in mitosis (the cell cycle). When cells commit to meiosis, DNA replicates.
- Regina Bailey
- Interphase. There are two stages or phases of meiosis: meiosis I and meiosis II. Before a dividing cell enters meiosis, it undergoes a period of growth called interphase.
- Prophase I. In prophase I of meiosis, the following events occur: Chromosomes condense and attach to the nuclear envelope. Synapsis occurs (a pair of homologous chromosomes lines up closely together) and a tetrad is formed.
- Metaphase I. In metaphase I of meiosis, the following events occur: Tetrads align at the metaphase plate. Note that the centromeres of homologous chromosomes are oriented toward the opposite cell poles.
- Anaphase I. In anaphase I of meiosis, the following events occur: Chromosomes move to the opposite cell poles. Similar to mitosis, microtubules such as the kinetochore fibers interact to pull the chromosomes to the cell poles.
Oct 31, 2023 · During meiosis II, the sister chromatids within the two daughter cells separate, forming four new haploid gametes. The mechanics of meiosis II is similar to mitosis, except that each dividing cell has only one set of homologous chromosomes.
Meiosis Consists of a Reduction Division and an Equational Division. Two divisions, meiosis I and meiosis II, are required to produce gametes (Figure 3). Meiosis I is a unique cell division...
