Meiosis Flashcards
What is meiosis?
The production of gametes
How does meiosis and mitosis differ regarding the number of chromosomes?
Mitosis is the division of a cell nucleus in which the number of chromosomes in the new daughter cell remains the same as that of the original mother cell. Meiosis is the division of a cell nucleus in which the number of chromosomes in the new daughter cell is reduced to half that of the original mother cell.
What is a diploid cell? A haploid cell?
A cell that has 46 chromosomes, or 23 pairs. A haploid cell contains only 23 chromosomes.
How are the chromosomes arranged in a diplod cell?
In a diploid cell, the chromosomes occur in pairs called homologous chromosomes (23 pairs in humans). Each homologous pair consists of one chromosome from the father and one chromosome from the mother. These chromosome pairs have the same length and their centromeres are located at the same site. The gene for a particular trait (such as eye color) is located at the same site on each chromosome but the type of that trait (like blue or brown eye color) might be different or the same on the two chromosomes.
How many divisions of the nucleus are there in meiosis?
- There is meiosis I and meiosis II and results in the production of four daughter cells each having the haploid number of chromosomes.
What are homologous chromosomes?
In a diploid cell, the chromosomes occur in pairs called homologous chromosomes (23 pairs in humans) Each homologous pair consists of one chromosome from the father and one chromosome from the mother. These chromosome pairs have the same length and their centromeres are located at the same site. The gene for a particular trait (such as eye color) is located at the same site on each chromosome but the type of that trait (like blue or brown eye color) might be different or the same on the two chromosomes.
What happens during crossing-over and is this process part of meiosis or mitosis?
During crossing over, genetic material is exchanged between sister chromatids, which no longer leaves them identical but diversely unique. This happens in meiosis.
What happens in prophase I ?
Chromosomes replicate to form two sister chromatids each joined at the centromere. Homologous chromosomes line up side by side and exchange genetic material (crossing-over). The cell has the diploid number of chromosomes.
What happens in metaphase I?
The homologous chromosomes move toward the metaphase plate with the maternal and paternal homologous chromosomes being randomly oriented toward either pole, allowing all possible combinations of chromosomes to occur in the daughter cells.
What happens in anaphase I ?
The homologous chromosomes separate and the chromosomes (still composed of two chromatids each) move to opposite poles.
What happens in telophase I ?
New nuclear membranes form around each set of separate chromosomes, the cleavage furrow deepens and the joined structure separates into two daughter cells. Each daughter cell now contains only one chromosome (composed of two chromatids) from each homologous pair. Each cell contains the haploid number of chromosomes.
Tell what happens in Prophase II?
Each chromosome with its two chromatids attaches to the developing spindle.
Tell what happens in metaphase II?
Chromosomes move to the metaphase plate
Tell what happens in anaphase II ?
The sister chromatids separate at the centromere and the resulting chromosomes move toward the poles
What happens in telophase II?
New nuclear membranes form around each set of separate chromosomes, the cleavage furrow deepens and the cells separate into four haploid daughter cells containing different sets of genes than the original cells
