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On August 6, 1945, the people of Hiroshima woke up to the burning smell of flesh of their husbands, wives, kids, parents, and neighbours as a result of the devastating effects of a little boy, an enriched fission bomb, that was dropped over the city by allied forces earlier. On the 9th of August, just three days after, the city of Nagasaki witnessed a similar misfortune, but this time, it was the fat man - a plutonium implosion-type nuclear weapon - that did the damage. There are diverse reports but a particular outlet estimated the total number of lives lost to be roughly over 170,000. Of course, the sheer destructive effects of the bombs led the Japanese government to surrender, effectively ending the Pacific war. The war might have ended, but its effects still linger. Scientists are actively still investigating the potential genetic effects of the bombing on the human, plant, and animal diversity in the region.

<center>https://innovativegenomics.org/wp-content/uploads/2018/04/Mutation.png</center>
<center><sup>[source](https://innovativegenomics.org/glossary/mutation/)</sup></center> 

#### Mutation
The morphological appearance and metabolic activities of every living organism are dictated by a set of instructions embedded in one of the biomolecules that make up the living organism - the deoxyribonucleic acid (DNA). The DNA is made up of nucleotide sequences that are not just random but organized in such a way as to pass specific instructions. It is this same molecule that dictates the traits that are passed from parents to offspring. As such, the molecule is designed in such a way that the sequence of nucleotides does not change easily, except under special conditions. A change in the nucleotide sequence of the DNA of organisms is what is scientifically known as mutation.

Not all mutations can be passed on to offspring. Mutations that occur in vegetative cells are limited to the concerned individuals only and cannot be passed on to offspring. Mutations that occur in the germline or reproductive cells, however, are usually passed on to future offspring.  

#### What are the things that can cause mutation?
The change to the sequence of DNA can occur either naturally or can be induced by external factors. The changes to the DNA sequence can result in 3 things:
1. It can be advantageous/beneficial to the individual.
2. It can be neutral; or
3. It can be deleterious to the individual

Most often, mutation results in the latter.

Naturally, mutation can occur during the process of making copies of organism's genetic materials. One of the attributes of DNA that makes it to effectively function as hereditary molecule is the ability to make copies of itself, a process known as replication. During this process, the original sequence of the molecule is used as templates to manufacture an exact copy, otherwise known as daughter DNA. While the entire process is  a carefully regulated and controlled one, mistakes do ocassionally occur while copying the nucleotide sequence.

Some mutation types can be induced by extertal stimuli, such as exposure to certain chemicals or radiations. Radiation-induced mutations are those currently being research in Hiroshima and Nagasaki as pointed out at the beginning of this article. The external stimuli cause the breakdwon of the DNA and while the cell's machinery tries its best to carryout a repair, some mistakes might occur along the way. 

While the mutations above can happen spontaneously, mutations can also be artificially induced using several methods, including
- Radiation method
- Chemical chemical
- Transposon insertion method

Radiations that have been used to induce mutations in the past include X-ray, gamma rays and neutron bombardment while chemical mutagens that have proven effective include alkylating agents such as ethyl methane sulphonate and ethyl ethane sulphonate and base analogs such as 5-bromouracil and 2-aminopurine. Transposons are pieces of gene-carrying DNA that are capable of moving from one place to another within the same or different genomes. The ability to move and insert themselves genomes is specifically exploited by scientists to induce a change in the genome sequence of organisms. 

#### Types of Mutation
Mutations are generally classified into two groups, namely;
1. Point mutation
2. Chromosomal mutation

Point mutation results when there is a single change to the  nucleotide sequence of DNAs. Point mutation can occur when a nucleotide is deleted, substituted, or inserted such that the original sequence of nucleotide is disrupted. 

Chromosomal mutation occur at the level of the chromosome. Parts of a chromosome might become deleted along with the genes it contains. Instead of deletion, segments of chromosomes can be duplicated, inverted, or translocated to another section of the chromosome. When all these happens, the order of genes on the chromosome becomes disrupted, repeated, inverted, or take any other form away from the original order. 

<center>https://cdn.pixabay.com/photo/2013/07/13/09/58/genetics-156404_960_720.png</center>
<center><sup>[source](https://pixabay.com/vectors/genetics-chromosomes-rna-dna-156404/)</sup></center>

#### Consequences of mutation
Like I said earlier, mutations can have consequences in the physical appearance of living organisms. Some mutations result in beneficial consequences for the affected organisms while some others result in deleterious consequences. When mutation leads to beneficial consequences, it leads to the evolution of the organism because natural selection pressure favours the mutated gene in the environment.

Lastly, some mutations have no consequences at all. In other words, they neither benefit or harm the organisms and they are otherwise known as silent mutations. In this case, a change in the nucleotide sequence of the DNA have no effect on the gene that the nucelotide sequence codes for.

#### Summary
Mutation refers to changes to the genome of organisms that can be natural as a result of error during the replication of the genome, induced by external environmental factors, or artificially induced by scientists for experimental purposes. Mutation can be point when a single nucleotide is altered in the genome. The alteration can be as a result of deletion, substitution, or insertion of a single nucleotide from or into the genome. Mutation can also be chromosomal when segments of gene-carrying chromosome is deleted, inverted, duplicated, or trnalocated to another location within the same genome or the genome of another individual. Mutations are often deleterious but can also be beneficial in nature while some are neither harmful nor beneficial - silent. When a germ-line mutation confers advantages on organisms, natural selection favours the mutated gene within the population and this leads to the evolution of organisms.

Thank you all for reading.
 

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### Resources
-https://biologydictionary.net/silent-mutation/
-https://en.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_and_Nagasaki  
- https://evolution.berkeley.edu/evolibrary/article/evo_20
- https://www.nature.com/scitable/topicpage/genetic-mutation-441/
- https://www.genome.gov/genetics-glossary/Point-Mutation
- https://www.ndsu.edu/pubweb/~mcclean/plsc431/mutation/mutation3.htm