Cell division and Forms of reproduction

Common terms :-

Cell divides into multiple copies as reproduction for replacing older/Damaged/dead ones and for growing larger or growing up into a new organism. There are different ways in which cells divide depending upon the intention.

Mitosis :- For example, when you have an injury your cells die and are replaced by newer one in a couple of days, this is Mitosis. Single mother cell divides into two cells.

Meiosis :-  All gametes (all animals) are formed by a different type of cell division called “Meiosis”. One single cell divides into 4 cells.

Reproduction :- Reproduction is producing more individuals of the same kind.

Chromosomes are organized chromatin material, made of DNA.

Haploid :-   Unpaired chromosomes

Diploid :-    Paired Chromosomes

Every organism is made up of cells. Every cell has a nucleus (with some exceptions). Nucleus is like brain of the cell and contains DNA. As I mentioned it in my other blog.

*DNA does contain all the information about the functions of a cell and how the body works but is not a blueprint. Reading DNA is not that easy for example in plants, the triggering of the chemical compound called auxin stimulates the growth of the shoot towards the sunlight as the auxin reacts more where there is light and thus directing the stem towards the sunlight and gibberellins react with ten other chemicals to spurt the growth. In humans, for instance, there are known ten or so hormones or chemicals that determine your height and this is just the crust of the DNA in many parts more than 50 to 100 chemicals react combining into the growth of your body. * 

Each individual has their own DNA and is unique from others. The cells which carry the DNA of the parent and fuse with the other is called a gamete. These gametes are formed through meiosis. Meaning they have half the chromosomes as their mother cells, thus are haploid (unlike their mother cells which are diploid).

 In sexual reproduction the DNA of both the parents are fused together and forms a new one. This means the child has different but similar DNA compared to the parents. IN asexual reproduction DNA of two parents is not mixed, since there is no fusion of DNA of two parents they don’t have gametes. The resulting offspring in asexual reproduction has always an exact copy of DNA of it’s parent, a clone. Types of asexual reproduction are :-

Binary fission :-  Single parent cell doubles its DNA, then divides into two cells. In this method, two similar individuals are produced from a single parent cell. Seen only in unicellular organisms like amoeba and bacteria.

Budding :-   In this process, a new organism is developed from a small part of the parent's body. A bud which is formed detaches to develop into a new organism. This seen in unicellular and multicellular organisms like Bacteria, yeast corals and even jellyfish.

Fragmentation :-   Fragmentation is simple words means the process of fragmenting—breaking into pieces or being divided into parts. In fragmentation a part of the organism’s detaches and grows into a new individual. It is seen in Lichens, sponges and also in a special type of Bacteria “Cyanobacteria” etc.

Parthenogenesis :- This a special type of reproduction in asexual mode. It has many types further in itself. What actually parthenogenesis is ………………………..

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J. Maanavendra roy,
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