4 Types Of Chromosomal Mutation

Call up of the human genome every bit a big library that has an immense corporeality of books containing the recipes to brand all the dissimilar proteins in our bodies. Sometimes, a recipe instruction gets changed by a mutation, and this change might lead to serious genetic disorders depending on the blazon of mutation.

Mutation definition

Before diving into the types of mutations, permit'south review the fundamentals of genetics. Dna is the genetic material constitute in the nucleus of a prison cell. Information technology consists of 2 strands coiled effectually each other in a double-helix. The structure of Dna (Figure ane) consists of chains of nucleotides. The complementary bases from each Deoxyribonucleic acid strand are joined together past hydrogen bonds.

A nucleotide consists of a sugar, a phosphate group, and a base of operations. There are four bases: adenine (A), guanine (Grand), thymine (T), and cytosine (C).

DNA contains genes, which are stretches of DNA that carry the data for a protein. Genes come in different forms called alleles. In diploid cells, there are two alleles per gene. For example, the combination of these ii alleles determines characteristics like centre color.

Alleles are different forms of the same gene.

Genes are located at a specific locus in chromosomes (Effigy 2). Diploid (2n) organisms have a pair of homologous chromosomes, and each chromosome of the pair carries dissimilar versions of the same genes (alleles).

The nucleus contains chromosomes , which contain DNA and are composed of chromatin.

Now, let's look at the definition of mutation.

Mutations are errors or changes in the genetic code.

These mutations tin touch somatic cells (any cells in the body apart from the gametes) or gametes. Mutations in gametes are called germline mutations, and tin can be passed on to the next generation.

What causes mutations? Mutations can be induced by mutagens such as UV rays, chemicals, or viruses, or they can occur spontaneously . Often, mutations occur during DNA replication, correct before a cell divides.

Mutations autumn into two categories: factor mutations and chromosomal mutations. Gene mutations are mutations that cause alteration of the nucleotide sequence of a genes, whereas c hromosomal mutations are mutations that produce changes in whole chromosomes.

Types of mutations in DNA

Mutations in Deoxyribonucleic acid are known as gene mutations. Gene mutations can be bespeak mutations or frameshift mutations.

A gene mutation is a change in the sequence of base pairs in a Dna molecule.

Point mutations (or base substitutions) are mutations involving the alteration of a single base of operations pair of DNA or of a few adjacent base of operations pairs. There are three main types of betoken mutations that you need to be familiar with:

Silent mutations: mutations that take no consequence on the amino acrid sequence.
Nonsense mutations: mutations that outcome in the change of 1 amino acrid into a stop codon.
Missense mutations: A mutation in which an amino acid is changed into a different one.

When dealing with base substitutions, the result depends on whether that base of operations pair replacement results in a new amino acid and how that amino acid affects the overall folding and function of the poly peptide.

To better empathise this, take a look a Figure 3. If we had a codon UGU, which codes for the amino acid cysteine and the last "U" got swapped for a "C", it would nonetheless effect in cysteine since UGC also codes for cysteine. In this case, the resulting poly peptide did not change, so nosotros phone call information technology a silent mutation.

However, if the last "U" in the codon UGU got replaced past an "A", and so it would result in UGA, which is a stop codon. Ribosomes stop building proteins when they encounter a stop codon. This kind of mutation is known every bit a nonsense mutation because it results in a shorter protein that cannot function properly.

Now, if the "One thousand" in UGU got substituted for an "A", it would result in UAU, which codes for the amino acrid tyrosine. In this case, we would call it a missense mutation.

Types of Mutations Figure 3. Point mutations Types of mutations in DNA StudySmarter Effigy 3. Point mutations, StudySmarter Originals.

In frameshift mutations, amino acid sequences in a poly peptide are completely contradistinct upon the insertion or deletion of a nucleotide. When a nucleotide gets added or deleted, the bases are yet read in groups of three. Nonetheless, those groupings shift in every codon that follows the mutation.

An insertion involves the addition of at least 1 nucleotide.
Deletions involve the removal of one or more than nucleotides.

Figure 4 shows an example of this. Notice that when no mutations are nowadays, nosotros have four codons:

Codon 1 (ACA) codes for the amino acid threonine.
Codon 2 (AAG) codes for lysine.
Codon 3 (AGA) codes for arginine
Codon iv (GGT) codes for glycine.

Now, if an insertion occurred and the base "G" got inserted correct afterward codon ane (ACA), all codons after the mutation until the end codon would be altered.

Codon ii would become GAA and code for Glutamic acid instead of lysine.
Codon iii would become GAG and code for Glutamic acid instead of lysine.
Codon 4 would become AGG and code for Arginine instead of glycine.

The same thing would happen is a deletion occurred. For case, if the first "A" in codon two got deleted, all codons would modify and code for unlike amino acids.

Bespeak mutation

Now that we know what betoken mutations are, allow'south look at some examples of disorders associated with it.

Cystic fibrosis is an example of a genetic disorder generally caused a indicate mutation involving a iii base pair deletion in the CFTR gene. Specifically, it deletes the amino acrid phenylalanine (Phe) at position 508. This mutation disrupts the chloride ion channels, resulting in the product of a viscous mucoid material that obstructs glandular ducts in salivary glands, bronchial glands, and pancreas.

Genetic changes found in cancers are sometimes besides caused by indicate mutations. The most common example is the point mutation that convert the RAS cistron into a cancer gene (Figure v). Another instance is the point mutation in tumor suppressor genes, leading to a reduction in its part. The tumor suppressor gene that is most affected past point mutations in cancer is called TP53.

Types of mutations Figure 5. Point mutation in RAS oncogene Point mutation StudySmarter Figure v. Betoken mutation in RAS oncogene, StudySmarter Originals.

Missense mutation

We saw above that missense mutations are point mutations caused past a substitution that leads to a modify in a unmarried amino acid. Sickle-jail cell disease is an example of a disease acquired past a missense mutation.

Sickle cell disease is a genetic disease in which hemoglobin molecules are abnormal and has a sickle shape. This sickle shape causes capillaries to clog, causing severe pain, weakness, and deterioration of vital organs. This illness is hereditary and gets passed on to offspring if both parent conduct the defective gene. Sickle cell affliction happens when a betoken mutation changes the hydrophilic amino acrid glutamic acid (Glu) for valine (Val), which is a hydrophobic amino acid (Figure six). This makes it hard for red blood cells to conduct as much oxygen.

Types of chromosomal mutation

On to chromosomal mutations. Often, chromosomal mutations can result in changes in the location or number of genes on chromosomes. Chromosome mutations fall into four categories: deletion, duplication, inversion, and translocation.

Chromosomal mutations are mutations that touch on multiple genes on a chromosome.

Chromosomal deletion mutations involve the loss of all or part of the chromosome, removing one or more genes from chromosome (Effigy seven). Deletions in human chromosomes can cause serious bug. For instance, a specific deletion in chromosome v causes cri du conversation ("cry of the cat") syndrome. This syndrome causes developmental disabilities, a high-pitched cry that sounds like that of a cat, and a pocket-size caput with unusual facial features.

Duplication mutations occur when a segment of a chromosome is copied and inserted into the homologous chromosome, resulting in extra genetic material (Figure viii). An example of a homo disorders caused by duplication mutation is Charcot-Marie-Tooth disease type 1A. This illness tin can be acquired by the duplication of the cistron encoding peripheral myelin protein 22 (PMP22) on chromosome 17. This disease causes progressive muscular and sensory loss in their legs and artillery.

In an inversion mutation, a segment of a chromosome gets removed and then reinserted opposite to its original orientation. The disorder hemophilia is an example of inversion mutation in humans that occur on the Ten chromosome factor F8 that codes for clotting factor Viii (Figure ix). Hemophilia is a genetic affliction characterized by the lack of one or more proteins required for blood clotting.

Lastly, nosotros have translocation mutation. This type of mutation happens when office of 1 chromosome breaks off and attached to another chromosome. For example, chronic myelogenous leukemia happens due to a translocation mutation that exchanges a portion of chromosome 22 with a fragment of the tip of chromosome ix, leading to uncontrolled cell growth (Figure x).

Examples of types of mutations

To finish off, let's explore some usually types of mutation in humans that you might not have even heard before!

Ectrodactyly, besides known every bit "lobster claw syndrome" is a mutation that causes "separate" hands and feet (Effigy eleven). Ectrodactyly is caused by deletions, translocation, or inversion mutations in chromosome 7.

A more severe, but rare genetic disorder is called Hutchinson-Gilford progeria. This affliction caused accelerated aging due to a mutation in the LMNA gene, a protein that provides support to the cell nucleus. Individuals suffering from progeria tend to dice around the historic period of 13, typically of a heart attack or stroke (Figure 12).

Types of Mutations - Cardinal takeaways

Mutations are errors or changes in the genetic code.
Mutations can arise spontaneously , or they can be induced by mutagens such as UV rays, chemicals, or even viruses.
Gene mutations are mutations that cause amending of the nucleotide sequence of a genes. Cistron mutations tin be bespeak mutations or frameshift mutations.
C hromosomal mutations are mutations that produce changes in chromosomes. There are four types of chromosomal mutations: deletion , duplication , inversion , and translocation .

References

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