Compared the process of mitosis with the process of meiosis and include answer with study of the change in chromosome number. Where do these changes occur and how are they relevant to the processes discussed?
I understand the comparing part, but then the change in chromosome i need help and the second question.
They probably want to know in which stage of meiosis the shift to a haploid number occurs. If you know the stages, this should be evident. If not, here are some sites:
http://fig.cox.miami.edu/~cmallery/150/mitosis/mitosis.htm
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20101/Bio%20101%20Laboratory/Mitosis/mitosis.htm
(Broken Link Removed)
http://www.vcbio.science.ru.nl/en/virtuallessons/meiostage/
I hope this helps. Thanks for asking.
I can definitely help you with understanding the changes in chromosome number and their relevance to the processes of mitosis and meiosis!
Both mitosis and meiosis are processes of cell division, but they have different outcomes and play distinct roles in different organisms. Let's compare the two processes and the changes in chromosome number they involve:
1. Mitosis:
Mitosis is a form of cell division that occurs in somatic (non-reproductive) cells, resulting in two genetically identical daughter cells. Here's an overview of how mitosis works:
- Interphase: Before mitosis begins, the cell undergoes a period of growth and DNA replication, during which the chromosomes are duplicated. Each chromosome consists of two identical sister chromatids joined at a region called the centromere.
- Prophase: The chromatin (uncoiled DNA) condenses into visible chromosomes, and the nuclear envelope begins to break down. The centrosomes move to opposite poles of the cell, and spindle fibers start to form.
- Metaphase: The chromosomes line up in the middle of the cell along the metaphase plate, with their centromeres attached to the spindle fibers.
- Anaphase: The sister chromatids separate and are pulled towards opposite poles of the cell by the shortening spindle fibers.
- Telophase: The two sets of chromosomes reach opposite poles, and a new nuclear envelope forms around each set. The chromosomes uncoil, and cytokinesis (division of the cytoplasm) occurs.
- Result: Two genetically identical daughter cells are produced, each containing the same number of chromosomes as the parent cell (diploid number).
In mitosis, the chromosome number remains constant throughout the process. This is important for growth, repair, and maintenance of the body's tissues and organs.
2. Meiosis:
Meiosis is a specialized form of cell division that occurs in germ cells (cells involved in sexual reproduction) to produce gametes (sperm and eggs). Meiosis involves two consecutive divisions (meiosis I and meiosis II) and results in the formation of four genetically diverse daughter cells. Here's an overview:
- Interphase: Similar to mitosis, the DNA is replicated, and each chromosome consists of two sister chromatids.
- Meiosis I: This is the reduction division where the chromosome number is reduced by half.
- Prophase I: Chromosomes condense, and homologous pairs form a bivalent through a process called synapsis. This allows for crossing over, where genetic material is exchanged between non-sister chromatids of homologous chromosomes. The nuclear envelope breaks down, and the spindle apparatus forms.
- Metaphase I: The bivalents line up along the metaphase plate, with each homologous pair of chromosomes independently attached to the spindle fibers.
- Anaphase I: Homologous chromosomes separate and move towards opposite poles of the cell.
- Telophase I: A nuclear envelope forms around each set of chromosomes, and cytokinesis occurs, resulting in two daughter cells.
- Meiosis II: This is similar to mitosis, but the resulting cells are haploid (having half the number of chromosomes as the parent cell).
- Prophase II, metaphase II, anaphase II, and telophase II occur, resulting in the separation of sister chromatids.
- Cytokinesis occurs, leading to the production of four haploid daughter cells, each with a unique combination of genes.
In meiosis, the chromosome number is halved during the first division (meiosis I). This reduction in chromosome number is crucial for sexual reproduction because when gametes fuse during fertilization, the resulting organism will have the correct number of chromosomes.
To summarize, in mitosis, the chromosome number remains constant, while in meiosis, the chromosome number is reduced by half. These changes in chromosome number are essential for the reproductive processes and genetic diversity in sexually reproducing organisms.