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The gametic (n) and somatic (2n) chromosome numbers remain constant in a species due to the correct mitotic and meiotic cell divisions. Gametes in a diploid organism possess only a single copy of each chromosome, however, somatic cells possess two copies of each chromosome.
The genomes of chromosomes are different in terms of their morphology and genetic content. However, homologous chromosomes genomes are identical and contain similar genes in the same sequence. Rarely, some spontaneous variations occur in chromosomes. These variations are known as genetic mutations.
In other words, a genetic mutation is defined as a permanent change in the genetic sequence that make up a gene. Genetic mutation can take place in two dissimilar ways: they can either be passed from a parent or acquired during a person’s life span. A mutation that is inherited from parents to child is called a germline mutation that involves the egg and sperm cells. Acquired mutations, on the other hand, occur in the DNA of each cell during a person’s life span. These variations can be influenced by environmental factors, including ultraviolet radiation from the sun, or DNA mismatch during cell division.
Following are additional facts about chromosomal mutations.
In addition, mutation can also take place inside an early embryo, but this may happen in a single cell. When each cell of the embryo divides, the individual will have some both mutated cells and normal cells.
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Do Genetic Mutations Affect Health?
In order to function normally, each cell is dependent on thousands of proteins to do their job in the right manner and at the right place. In genetic mutations, however, some mutated genes prevent some proteins from working properly. When a gene disrupts the functioning of proteins to perform a particular function, it can disrupt normal development and pose medical problems.
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Are Genetic Mutations Fatal?
Genetic mutations are not necessarily fatal and, in fact, only a few mutations cause disorders. For example, some gene mutations only change a gene’s base sequence, but do not change a protein’s functionality. Most often genetic mutations that might cause disorder are repaired before gene expression.
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What Does It Mean If a Genetic Disorder Runs In My Family?
If a particular disorder runs in a family, it means that more than one person in the family is affected. The disorder that affects more than one member of a family is caused because of genetic mutation which can be inherited. Environmental factors may be responsible for some disorders, so it is not easy to determine if a particular disorder is inherited or not. A genetic professional can study the person’s family history to know whether the disorder is inherited or not.
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What Is the Probability That My Children Will Inherit the Condition?
It is not an easy task to determine the likelihood that the parents’ children will develop the same condition. There are several factors that decide or influence a person’s probability of developing a disorder. For example, in autosomal dominance inheritance, a person affected with in this manner has a 50 percent chance of passing the mutated gene to each child. However, in autosomal recessive inheritance, the parent carries the defective gene and has a 25 percent chance of passing the disorder to each child. But the chance of unaffected child carrying the mutated gene is 50 percent.
On the other hand, the chance of inheriting an X-linked recessive disorder varies between men and women. If an affected father and unaffected mother have four children (2 sons and 2 girls) then both the sons would be unaffected and both the daughters would carry the mutated gene.
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(Web): Mutations and Health -- http://ghr.nlm.nih.gov/handbook/mutationsanddisorders
(Web): A Mutated Gene -- http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/MUT/Mut.Mutation.html