WHAT IS A MUTATION?
A mutation is a permanent, genetic change in the nucleotide sequence in a chromosome or gene. A mutation is an unexpected alteration/change in the structure or amount of genetic material.
POTENTIAL CAUSES OF MUTATIONS
Mutations seem to occur naturally at a low rate, but many factors can increase the probability of a genetic mutation being found in the body. The factors that cause this increase in probability are called ‘mutagens’. Possible exogenous mutagens include radiation (such as UV rays and X-rays), high heat, carcinogens and chemicals. Some endogenous factors are errors during DNA replication, which can result in genetic changes as well as toxic by-products of cellular metabolism.
DIFFERENT TYPES OF MUTATIONS (CHROMOSOMAL + GENE MUTATIONS)
Chromosomal Mutations:
Permanent alterations in chromosome structure occasionally occur during cell division. Chromosomes might tangle or rearrange in different sequences which causes the chromosome to be misread. A few types of chromosomal mutations include:
- Translocation: The accidental attachment of a section of one chromosome to another chromosome. The segment is moved from one position to either a section on the same chromosome or on another. There are two types of translocation: reciprocal (when two segments swap positions with each other) and Robertsonian (when two chromosomes become attached to each other).
- Addition: The accidental repetition or reappearance of a section of the chromosome. This can cause a change in the amino acid sequence at protein translation.
- Deletion: A section of the chromosome accidentally disconnects (breaks away), leaving a partially complete chromosome. Deletion is the loss of genetic information.
- Inversion: The unintended reversal of different parts of the chromosome. It happens when one chromosome experiences a breakage and rearrangement in itself. Paracentric and pericentric are the two types of inversions that can occur.
Most chromosomal diseases form suddenly from parents where neither parent has the disease. Large genetic mistakes usually occur in the female’s ovum, which might partly explain the reason of why older women are have a higher probability to have offspring with Down syndrome. Some other chromosomal diseases apart from Down syndrome include Turner syndrome, Jacobs syndrome and Klinefelter syndrome.
Gene Mutations:
Genes, which are found inside chromosomes, are composed of thousands of different nitrogen bases which make up a DNA strand. If any change occurs in this sequence, it will alter the message given to the mRNA, which will result in a change of the amino acids that are coded to the sequence to assemble a specific protein. One small change in this order can alter the entire protein, or at least cause a malfunctioning protein. Some types of gene mutations are:
- Point Mutation: When one of the base pairs are changed. Point mutations can have one of three effects: the base substitution could be a missense mutation where the changed codon corresponds to a different amino acid; the base substitution can be a silent mutation where the changed codon corresponds to the same amino acid; or the base substitution can be a nonsense mutation where the changed codon corresponds to a stop codon (nucleotide triplet within mRNA that indicates translation to stop).
- Frameshift Mutation: It is caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that are not divisible by three. They are also called framing errors or reading frame shifts.
A common example of gene mutations, specifically point mutation, is the sickle cell disease. It occurs when one of the nucleotides is changed in the gene for hemoglobin. This point mutation causes hemoglobin in red blood cells to appear as a sickle shape when deoxygenated. The sickle-shaped blood cells clog in the capillaries of the affected person, cutting off circulation. Having two copies of the mutated genes causes sickle-cell anemia, but if you have just one copy, it does not and can beneficial to the person since it defends them against malaria.
A mutation is a permanent, genetic change in the nucleotide sequence in a chromosome or gene. A mutation is an unexpected alteration/change in the structure or amount of genetic material.
POTENTIAL CAUSES OF MUTATIONS
Mutations seem to occur naturally at a low rate, but many factors can increase the probability of a genetic mutation being found in the body. The factors that cause this increase in probability are called ‘mutagens’. Possible exogenous mutagens include radiation (such as UV rays and X-rays), high heat, carcinogens and chemicals. Some endogenous factors are errors during DNA replication, which can result in genetic changes as well as toxic by-products of cellular metabolism.
DIFFERENT TYPES OF MUTATIONS (CHROMOSOMAL + GENE MUTATIONS)
Chromosomal Mutations:
Permanent alterations in chromosome structure occasionally occur during cell division. Chromosomes might tangle or rearrange in different sequences which causes the chromosome to be misread. A few types of chromosomal mutations include:
- Translocation: The accidental attachment of a section of one chromosome to another chromosome. The segment is moved from one position to either a section on the same chromosome or on another. There are two types of translocation: reciprocal (when two segments swap positions with each other) and Robertsonian (when two chromosomes become attached to each other).
- Addition: The accidental repetition or reappearance of a section of the chromosome. This can cause a change in the amino acid sequence at protein translation.
- Deletion: A section of the chromosome accidentally disconnects (breaks away), leaving a partially complete chromosome. Deletion is the loss of genetic information.
- Inversion: The unintended reversal of different parts of the chromosome. It happens when one chromosome experiences a breakage and rearrangement in itself. Paracentric and pericentric are the two types of inversions that can occur.
Most chromosomal diseases form suddenly from parents where neither parent has the disease. Large genetic mistakes usually occur in the female’s ovum, which might partly explain the reason of why older women are have a higher probability to have offspring with Down syndrome. Some other chromosomal diseases apart from Down syndrome include Turner syndrome, Jacobs syndrome and Klinefelter syndrome.
Gene Mutations:
Genes, which are found inside chromosomes, are composed of thousands of different nitrogen bases which make up a DNA strand. If any change occurs in this sequence, it will alter the message given to the mRNA, which will result in a change of the amino acids that are coded to the sequence to assemble a specific protein. One small change in this order can alter the entire protein, or at least cause a malfunctioning protein. Some types of gene mutations are:
- Point Mutation: When one of the base pairs are changed. Point mutations can have one of three effects: the base substitution could be a missense mutation where the changed codon corresponds to a different amino acid; the base substitution can be a silent mutation where the changed codon corresponds to the same amino acid; or the base substitution can be a nonsense mutation where the changed codon corresponds to a stop codon (nucleotide triplet within mRNA that indicates translation to stop).
- Frameshift Mutation: It is caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that are not divisible by three. They are also called framing errors or reading frame shifts.
A common example of gene mutations, specifically point mutation, is the sickle cell disease. It occurs when one of the nucleotides is changed in the gene for hemoglobin. This point mutation causes hemoglobin in red blood cells to appear as a sickle shape when deoxygenated. The sickle-shaped blood cells clog in the capillaries of the affected person, cutting off circulation. Having two copies of the mutated genes causes sickle-cell anemia, but if you have just one copy, it does not and can beneficial to the person since it defends them against malaria.