Cell division and diversity

• Mitosis plays a role in living organisms by duplicating and distributing genetic information.
• The stages of cell division by mitosis can be described as follows: Prophase, Metaphase, Anaphase, and Telophase.
• Mitosis is a complex process that can be understood by breaking it down into its individual stages.
• Chromosomes are important in mitosis as they contain the genetic information that is duplicated and distributed during the process.
• Most organisms, including humans, contain more than two pairs of chromosomes in their cells.
• In a cell about to undergo division by mitosis, there can be any number of chromosomes, as long as they are arranged in pairs.
• When cells contain chromosomes and pairs, scientists refer to them as diploid cells.
• Cell division by mitosis starts with one diploid cell and ends with two identical diploid cells.
• Mitosis is used in asexual reproduction, as seen in aphids.
• Mitosis is part of a larger process called the cell cycle, which has two main phases: G1 Phase and G2 Phase.
• Both mitosis and cytokinesis take place during the M phase of the cell cycle.
• In the mitotic phase, the cell undergoes two processes: the nucleus divides into two daughter nuclei and the cell divides into two daughter cells, each with a nucleus.
• During interphase, the cell cannot see chromosomes in the nucleus, as they are not visible as distinct structures.
• Instead, scientists see a dark material called chromatin in the nucleus, which contains the chromosomes in a loose, open structure, making the DNA accessible for transcription and replication.
• The term mitosis specifically refers to the division of the nucleus, while the division of the cell is called cytokinesis.
• During interphase, chromosomes are replicated, resulting in two identical molecules of DNA, which scientists call sister chromatids.
• This process happens for every single chromosome and in humans, that means 23 pairs of chromosomes.
• During interphase, the cell increases its energy stores and grows in size, replicates its organelles and copies its DNA.
• This process takes place during interphase and the chromosomes are not visible as distinct structures at this stage.
• The point where the sister chromatids are joined is called the centromere.
• After interphase, the nucleus divides into two by mitosis.
• Cell division by meiosis only takes place in sex organs and is used to produce gametes, such as sperm and eggs.
• In cell division by meiosis, a diploid cell with pairs of chromosomes is transformed into four haploid gametes, each containing individual chromosomes.
• All the gametes made by meiosis are genetically different.
• During fertilization, gametes fuse together to produce a fertilized egg or zygote, and because gametes are haploid, the zygote has the diploid number of chromosomes.
• Both chromosomes in a homologous pair have exactly the same genes, but the alleles can be different.
• The gametes produced by meiosis are genetically different because parts of the chromosomes can break off and exchange alleles during the process of crossing over.