Structural Chromosomal Mutations

on health, depending on where they occur and whether they alter the function of essential proteins.

• MISSENSE MUTATION. REPEAT EXPANSION.
• DUPLICATION.
• DELETION. FRAMESHIFT MUTATION.
• INSERTION. NONSENSE MUTATION.

The three major single-chromosome mutations: deletion (1), duplication (2) and inversion (3). The two major two-chromosome mutations: insertion (1) and translocation (2).

• Deletion. This type of mutation occurs when a part of the DNA is not duplicated or is lost during DNA replication.
• Duplication. This type of mutation occurs when an extra copy of a region (or regions) in the DNA is produced.
• inversion.
• Translocation.

A silent mutation is a mutation in which a single nucleotide base is changed, but that change does not effect the amino acid sequence. A missense mutation is a point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid.

A mutagen is defined as an agent that causes irreversible and heritable changes (mutations) in the cellular genetic material, deoxyribonucleic acid (DNA).

Mutations are changes in the DNA of an organism. Mutations can be beneficial, benign, or malignant, depending on where in the genetic code they are located. Examples of beneficial mutations include HIV resistance, lactose tolerance, and trichromatic vision.

The genetic mutation that drives evolution is random. But here’s a list of some beneficial mutations that are known to exist in human beings

• Beneficial mutation #2: Increased bone density.
• Beneficial mutation #3: Malaria resistance.
• Beneficial mutation #4: Tetrachromatic vision.

Deletion mutations, on the other hand, are opposite types of point mutations. They involve the removal of a base pair. Both of these mutations lead to the creation of the most dangerous type of point mutations of them all: the frameshift mutation.

But the mutations we hear about most often are the ones that cause disease. Some well-known inherited genetic disorders include cystic fibrosis, sickle cell anemia, Tay-Sachs disease, phenylketonuria and color-blindness, among many others. All of these disorders are caused by the mutation of a single gene.

Insertion or deletion results in a frame-shift that changes the reading of subsequent codons and, therefore, alters the entire amino acid sequence that follows the mutation, insertions and deletions are usually more harmful than a substitution in which only a single amino acid is altered.

In fact, the G-T mutation is the single most common mutation in human DNA. It occurs about once in every 10,000 to 100,000 base pairs — which doesn’t sound like a lot, until you consider that the human genome contains 3 billion base pairs.

A deletion changes the DNA sequence by removing at least one nucleotide in a gene. Small deletions remove one or a few nucleotides within a gene, while larger deletions can remove an entire gene or several neighboring genes. The deleted DNA may alter the function of the affected protein or proteins.

Mutational effects can be beneficial, harmful, or neutral, depending on their context or location. Most non-neutral mutations are deleterious. In general, the more base pairs that are affected by a mutation, the larger the effect of the mutation, and the larger the mutation’s probability of being deleterious.