Question

What is point mutation? Give one example.

Answer 1

Mutation refers to the alternation of gene sequences or a change in the nucleotide sequences that causes a change in the structure of DNA; this might refer even to entire sections of chromosomes.

Complete answer:
A point mutation is a mutation in DNA or RNA, the cell’s genetic material, during which one single nucleotide base is added, deleted, or changed.
Point mutations are an outsized category of mutations that describe a change in a single nucleotide of DNA, such that nucleotide is switched for an additional nucleotide, or that nucleotide is deleted or inserted into the DNA that causes that DNA to vary from the traditional gene sequence.

From DNA to Protein:
DNA and RNA have a double helix structure. They are made up of nucleotides. Five different molecules will structure nitrogenous bases on nucleotides: cytosine, guanine, adenine, thymine (in DNA), and uracil (in RNA). The specific sequence of nucleotides encodes all the knowledge for completing all cell processes therefore, it's important to correct pairing of the bottom pairs to make proteins correctly.
Sometimes point mutations are caused by mutations occurring during DNA replication. The rate of mutations can also increase when a cell is exposed to mutagens, which are environmental factors which will change an organism’s DNA.

Example: Sickle-Cell Anemia:
Sickle-cell anemia may be a recessive disorder caused by one substitution within the gene that makes hemoglobin, which carries oxygen within the blood. Normally, glutamic acid is produced within the chain, but the substitution causes valine to be produced at that spot instead. When people have two copies of this mutation, it leads to thin sickle-shaped blood cells that sometimes cannot carry oxygen properly.

Additional information:
Types of Point Mutations:
There are two sorts of point mutations: transition mutations and transversion mutations.

Transition mutations occur when a pyrimidine base (i.e., thymine [T] or cytosine [C]) substitutes for an additional pyrimidine base or when a purine base (adenine [A] or guanine [G]) substitutes for another purine base. In ds-DNA each of the bases pairs with a selected partner on the corresponding strand—A pairs with T and C pairs with G. Thus, an example of a transition mutation may be a GC nucleotide that replaces a wild type (or naturally occurring) AT nucleotide.

The transversion mutations occur when a purine base substitutes for a pyrimidine base or vice versa. In translation, when RNA copied from DNA is converted into a string of amino acids during protein synthesis, point mutations manifest as functional changes within the final protein product. Thus, there exist functional groupings for point mutations. These groupings are divided into silent mutations, missense mutations, and nonsense mutations.

Note: Some scientists recognize frameshift mutation, as a type of point mutation. Frameshift mutations can cause a drastic loss of function and occur through the addition or deletion of 1 or more DNA bases.