Mitosis is common to all eukaryotes; during this process, a parent cell splits into two genetically identical daughter cells, each of which contains the same number of chromosomes as the parent cell. Meiosis, on the other hand, only occurs in eukaryotic organisms that reproduce sexually.

Eukaryotic DNA replication of chromosomal DNA is central for the duplication of a cell and is necessary for the maintenance of the eukaryotic genome. DNA replication is the action of DNA polymerases synthesizing a DNA strand complementary to the original template strand.

Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two genetically identical cells. In meiosis, DNA replication is followed by two rounds of cell division to produce four haploid daughter cells.

In eukaryotes — including humans — almost all cell division includes mitosis. Certain specialized cells called germ cells can also divide replicated DNA through meiosis, which results in specialized cells containing only one copy of each chromosome.

Mitosis and meiosis are similar in that both can only occur in eukaryotic cells. This is because prokaryotic cells do not contain a nucleus within which to begin the processes of mitosis and meiosis.

Of all eukaryotic organelles, the nucleus is perhaps the most critical. In fact, the mere presence of a nucleus is considered one of the defining features of a eukaryotic cell. This structure is so important because it is the site at which the cell’s DNA is housed and the process of interpreting it begins.

The division cycle of most eukaryotic cells is divided into four discrete phases: M, G1, S, and G2. M phase (mitosis) is usually followed by cytokinesis. S phase is the period during which DNA replication occurs.

In eukaryotic cells, or cells with a nucleus, the stages of the cell cycle are divided into two major phases: interphase and the mitotic (M) phase.

Eukaryotes have two major types of cell division: mitosis and meiosis. Mitosis is used to produce new body cells for growth and healing, while meiosis is used to produce sex cells (eggs and sperm).

The S phase of a cell cycle occurs during interphase, before mitosis or meiosis, and is responsible for the synthesis or replication of DNA. In this way, the genetic material of a cell is doubled before it enters mitosis or meiosis, allowing there to be enough DNA to be split into daughter cells.

Synthesis Phase

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. DNA and histone proteins are packaged into structures called chromosomes.

DNA is tightly packed up to fit in the nucleus of every cell. As shown in the animation, a DNA molecule wraps around histone proteins to form tight loops called nucleosomes. Condensing DNA into chromosomes prevents DNA tangling and damage during cell division.

46 chromosomes

Chromatin is a complex formed by histones packaging the DNA double helix. Chromosomes are structures of proteins and nucleic acids found in the living cells and carry genetic material. Chromatin is composed of nucleosomes. Chromosomes are composed of condensed chromatin fibers.

Chromatin is a complex of macromolecules composed of DNA, RNA, and protein, which is found inside the nucleus of eukaryotic cells.

Both DNA and RNA have four nitrogenous bases each—three of which they share (Cytosine, Adenine, and Guanine) and one that differs between the two (RNA has Uracil while DNA has Thymine). One of the most significant similarities between DNA and RNA is that they both have a phosphate backbone to which the bases attach.

Chromatin is only found in eukaryotic cells, with prokaryotic cells having a different arrangement of their genetic material called a genophore – a chromosome that doesn’t contain chromatin.

Heterochromatin

A) In eukaryotes, histones are poorly conserved. There are at least five different classes of histones. C) Histones in the Tetrahymena macronucleus have a very high level of acetylation.

DNA replication occurs during the S-stage of interphase. DNA replication (DNA amplification) can also be performed in vitro (artificially, outside a cell). DNA polymerases isolated from cells and artificial DNA primers can be used to start DNA synthesis at known sequences in a template DNA molecule.