Why do cells reproduce in a growing organism

A light microscope can be used to observe cells during the cell cycle. The DNA is stained so it can be seen more clearly. When looking down the microscope, the presence of individual chromosomes shows that the cell is in the mitosis stage of the cell cycle. If chromosomes cannot be seen then the cell is in interphase. Cancer is a non-communicable disease that is caused by changes in a person's DNA.

Normally, cells only divide if they get the correct signal. The DNA-histone complex is called chromatin. The beadlike, histone DNA complex is called a nucleosome. A DNA molecule in this form is about seven times shorter than the double helix without the histones. The beads are about 10 nm in diameter, in contrast with the 2-nm diameter of a DNA double helix. The next level of compaction occurs as the nucleosomes and the linker DNA between them are coiled into a nm chromatin fiber.

This coiling further shortens the chromosome so that it is now about 50 times shorter than the extended form. In the third level of packing, a variety of fibrous proteins is used to pack the chromatin. These fibrous proteins also ensure that each chromosome in a non-dividing cell occupies a particular area of the nucleus that does not overlap with that of any other chromosome. When a cell undergoes mitosis, the chromosomes condense even further. DNA replicates in the S phase of interphase.

After replication, the chromosomes are composed of two linked sister chromatids. When fully compact, the pairs of identically-packed chromosomes are bound to each other by cohesin proteins.

The connection between the sister chromatids is closest in a region called the centromere. The centromeric region is highly condensed and will appear as a constricted area. Privacy Policy. Skip to main content. Cell Reproduction. Search for:. Cell Division. The Role of the Cell Cycle The cell cycle allows multiicellular organisms to grow and divide and single-celled organisms to reproduce.

Key Takeaways Key Points All multicellular organisms use cell division for growth and the maintenance and repair of cells and tissues. Somatic cells divide regularly; all human cells except for the cells that produce eggs and sperm are somatic cells. Somatic cells contain two copies of each of their chromosomes one copy from each parent. During interphase, the cell grows and DNA is replicated; during the mitotic phase, the replicated DNA and cytoplasmic contents are separated and the cell divides.

All living organisms are capable of growing and producing offspring. All eukaryotic organisms—including aquatic plants and algae—grow through the process of mitosis. Mitosis is a process where one cell divides into two cells Fig. Chromosomes in the original cell are duplicated to ensure that the two new cells have full copies of the necessary genetic information. The process of mitosis generates new cells that are genetically identical to each other.

Mitosis helps organisms grow in size and repair damaged tissue. Some species of algae are capable of growing very quickly. The giant kelp Macrocystis pyrifera can grow as much as 30 centimeters cm in length in a single day. Some organisms can use mitosis to reproduce asexually. The offspring of asexual reproduction are genetically identical to each other and to their parent. Most single-celled, microorganisms reproduce asexually by duplicating their genetic material and dividing in half.

For example, phytoplankton reproduce primarily through asexual reproduction. Some single-celled eukaryotes, including some plants and animals, reproduce asexually in a processes called fragmentation or budding. Sexual reproduction is the production of offspring through the combination of sex cells or gametes.

Every human, as well as every sexually reproducing organism, begins life as a fertilized egg embryo or zygote. Trillions of cell divisions subsequently occur in a controlled manner to produce a complex, multicellular human. In other words, that original single cell is the ancestor of every other cell in the body. Single-celled organisms use cell division as their method of reproduction.