Information

10.5: What is a Mutation? - Biology

10.5: What is a Mutation? - Biology


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Learning Outcomes

Understand what a mutation is and how one generally occurs

Over a lifetime, our DNA can undergo changes or mutations in the sequence of bases: A, C, G and T. This results in changes in the proteins that are made. This can be a bad or a good thing.

A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke. Mutations can occur during DNA replication if errors are made and not corrected in time. Mutations can also occur as the result of exposure to environmental factors such as smoking, sunlight and radiation. Often cells can recognize any potentially mutation-causing damage and repair it before it becomes a fixed mutation.

Mutations contribute to genetic variation within species. Mutations can also be inherited, particularly if they occur in a germ cell (reproductive egg or sperm). Mutations that have a positive effect are more likely to be continually passed on. For example, the disorder sickle cell anaemia is caused by a mutation in the gene that instructs the building of a protein called hemoglobin. This causes the red blood cells to become an abnormal, rigid, sickle shape. However, in African populations, having this mutation also protects against malaria.

However, mutation can also disrupt normal gene activity and cause diseases, like cancer. Cancer is the most common human genetic disease; it is caused by mutations occurring in a number of growth-controlling genes. Sometimes faulty, cancer-causing genes can exist from birth, increasing a person’s chance of getting cancer.

An illustration to show an example of a DNA mutation. Image credit: Genome Research Limited


Mutation

What Kinds of Mutations Occur and What are their Consequences?

A mutation can be described by its genotype, that is, what kind of sequence change occurred? For convenience, mutations are frequently subdivided into categories by both size and kind of change. This convention derives, in part, from the fact that the mechanisms that lead to different kinds and sizes of mutations are often different.

Point mutations modify one or a small number of base pairs (bps), but larger DNA sequence deletions, additions, or rearrangements also occur. These more extensive mutations may be restricted to a single gene but when they exceed the size of a single gene, they are called multilocus mutations. In organisms whose genomes consist of multiple chromosomes, the information in a whole or part of a chromosome can be lost, duplicated, rearranged, or translocated to a different chromosome. The long-term consequences of these chromosomal changes can be appreciated by comparing evolutionarily related sequences. For example, man and mouse have different numbers of chromosomes and the order of genes on chromosomes is sometimes different, despite the fact that many genes are very similar.

Mutations are sometimes also described by their phenotype, that is, what are the consequences of the mutation? Phenotype is a secondary characteristic of a mutation and relies on the position of the mutation in the DNA of the organism. For example, the substitution of an adenine–thymine (A T) for a guanine–cytosine (G C) base pair might have absolutely no discernible consequence, or it might change an amino acid in a protein, which may or may not alter its function. Such a substitution, at a different location, might also alter the expression level of a protein or might prevent the production of a protein entirely. The differences depend on the whereabouts of the base substitution in the DNA sequence.

Point-mutation genotypes include base-pair substitutions, additions, or losses, and base-pair sequence inversions or complex changes.


DNA Mutations

DNA mutations are permanent changes in the DNA sequence of a gene. Mutations range in their severity. Some damage the way a cell or whole organism functions, or even cause lethality, while others have no effect. Mutations also range in the amount of DNA altered. They can involve from a single nucleotide up to large segments of chromosomes. DNA mutations can be:

Image Courtesy of Wikimedia Commons

* Inherited: parents that have mutations can pass them to their offspring.
* Germ line mutations: are present in every cell of an individual, including the egg or sperm used in the production of offspring.
* De novo (new) mutations: occur by chance in one or a few eggs or sperm, or just after fertilization, and are NOT present in every cell of a parent. These explain situations where a child has a genetic disorder that is unseen in the family history.
* Acquired: environmental agents, called mutagens, can alter DNA. An example of a common mutagen are the UV wavelengths in sunlight associated with skin cancer (see image). Acquired mutations are typically not passed to offspring but can be if they alter DNA sequences in egg or sperm.

* Insertion/Duplication/Deletion: the addition or subtraction of nucleotides from DNA sequence. They can be as small as single nucleotides or large enough to visualize on a chromosome and involve tens to hundreds of thousands of nucleotides.
* Point Mutation: the change in one nucleotide for another. For example, an “A” becomes a “T”.
* Translocation: the movement of a segment of DNA from one chromosome to another.
* Inversion: the 180° flip of a DNA segment so that that it is reversed compared to the original structure.

Ultimately whether or not a particular mutation causes a detrimental effect is due to the location of the mutation within a gene (or genes) as well as the significance of that gene’s function.


What is a mutation?

A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.

  • Over a lifetime our DNA can undergo changes or ‘mutations’ in the sequence of bases, A, C, G and T.
  • This results in changes in the proteins that are made. This can be a bad or a good thing.
  • Mutations can occur during DNA replication if errors are made and not corrected in time.
  • Mutations can also occur as the result of exposure to environmental factors such as smoking, sunlight and radiation.
  • Often cells can recognise any potentially mutation-causing damage and repair it before it becomes a fixed mutation.
  • Mutations contribute to genetic variation within species.
  • Mutations can also be inherited, particularly if they have a positive effect.
  • For example, the disorder sickle cell anaemia is caused by a mutation in the gene that instructs the building of a protein called haemoglobin. This causes the red blood cells to become an abnormal, rigid, sickle shape. However, in African populations, having this mutation also protects against malaria.
  • However, mutation can also disrupt normal gene activity and cause diseases, like cancer
  • Cancer is the most common human genetic disease it is caused by mutations occurring in a number of growth-controlling genes. Sometimes faulty, cancer-causing genes can exist from birth, increasing a person’s chance of getting cancer.

An illustration to show an example of a DNA mutation.
Image credit: Genome Research Limited


Watch the video: Δομή και βιολογική δράση των ιών - Βιολογία (September 2022).


Comments:

  1. Clyford

    You are certainly entitled

  2. Keiran

    Really and as I have not realized earlier

  3. Raedeman

    Excuse, I thought and pushed the question away

  4. Gror

    Brilliant phrase and it is duly



Write a message