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Mutation:
Mutations occur at a gene or chromosomal level and involve a change in a DNA sequence. It can happen in all organisms is also the source of new genetic variation. A change in the genetic code in DNA can cause a different type of protein to be coded for and created by that segment of DNA. This leads to a change in characteristics. Mutations that take place on germline cells (including sperm and eggs) are what produces new alleles within a population. The diagram below shows a change in the DNA sequence resulting in a different protein being coded for and created and changing the phenotype of the mouse from having white fur to having black fur.
Potential causes of mutation:
Mutations may occur by chance of have a specific cause. A spontaneous mutation is one in which the cause cannot identified. An induced mutation is one in which the cause can be identified. The cause of a mutation within a cell is described as a mutagen or mutagenic agent.
Common mutagenic agents include:
- Radiation (Ultra-violet radiation, nuclear radiation and x-rays)
- Chemical substances (Formalin and benzene)
Due to the thinning of the ozone layers, humans have become further exposed to ultra-violet radiation from the sun that can mutate our DNA. This mutation can result in the development of skin cancers.
Different types of mutation and examples of each (chromosomal and gene):
Point mutation (Gene mutation): a mutation that only occurs at one particular point in the DNA sequence. Errors in DNA replication may happen as the instructions in the code being copied are not followed completely.
Point mutations occur in 3 ways in which nitrogenous bases are not paired correctly:
- Substitution: when one nucleotide is exchanged for different one in a DNA sequence.
- Insertion: when an additional nucleotide is inserted into the original nucleotide sequence in DNA.
- Deletion: when a nucleotide is deleted from a sequence of DNA.
Chromosomal mutation: a mutation that involves the increase or decrease in the number of chromosomes in the cells of the person or the change in genetic information of entire chromosomes.
This involves:
- The addition or deletion of entire chromosomes.
- The addition, deletion or mixing of genetic information from segments of chromosomes.
Chromosomal mutations can result in a disorder within the person. For example, if an individual receives an extra copy of chromosome 21, that individual will develop Down syndrome.
Relationship between mutation and genetic variation:
Some mutations can increase an organism’s chance of survival. An organism that obtains a characteristic by mutation that increases its chances of survival is more likely to live long enough to have offspring. If the offspring then inherits this trait, its chances of survival are also increased. Over a period of time, more of the population will possess this advantageous trait. It is through mutation that organisms have become resistant to the methods humans use to kill them or control the size of their population. Then these organisms live long enough to reproduce and pass on this resistance trait. Over time, more of this specie’s population possesses the trait and the control methods used by humans can no longer be used. Mutation is the only way that variation can occur within asexually reproducing organisms. Asexually reproducing organisms produce clones that are genetically identical unless a mutation occurs. A change or error in the DNA sequence in cell division can provide new alleles. Variation caused by mutation can also benefit sexually reproducing organisms. A mutation may allow a species such as insects to become resistant to pesticides. This resistance trait can then be passed on to their offspring. As more of the population inherit the resistance trait, the control method becomes increasingly ineffective.
Mutations occur at a gene or chromosomal level and involve a change in a DNA sequence. It can happen in all organisms is also the source of new genetic variation. A change in the genetic code in DNA can cause a different type of protein to be coded for and created by that segment of DNA. This leads to a change in characteristics. Mutations that take place on germline cells (including sperm and eggs) are what produces new alleles within a population. The diagram below shows a change in the DNA sequence resulting in a different protein being coded for and created and changing the phenotype of the mouse from having white fur to having black fur.
Potential causes of mutation:
Mutations may occur by chance of have a specific cause. A spontaneous mutation is one in which the cause cannot identified. An induced mutation is one in which the cause can be identified. The cause of a mutation within a cell is described as a mutagen or mutagenic agent.
Common mutagenic agents include:
- Radiation (Ultra-violet radiation, nuclear radiation and x-rays)
- Chemical substances (Formalin and benzene)
Due to the thinning of the ozone layers, humans have become further exposed to ultra-violet radiation from the sun that can mutate our DNA. This mutation can result in the development of skin cancers.
Different types of mutation and examples of each (chromosomal and gene):
Point mutation (Gene mutation): a mutation that only occurs at one particular point in the DNA sequence. Errors in DNA replication may happen as the instructions in the code being copied are not followed completely.
Point mutations occur in 3 ways in which nitrogenous bases are not paired correctly:
- Substitution: when one nucleotide is exchanged for different one in a DNA sequence.
- Insertion: when an additional nucleotide is inserted into the original nucleotide sequence in DNA.
- Deletion: when a nucleotide is deleted from a sequence of DNA.
Chromosomal mutation: a mutation that involves the increase or decrease in the number of chromosomes in the cells of the person or the change in genetic information of entire chromosomes.
This involves:
- The addition or deletion of entire chromosomes.
- The addition, deletion or mixing of genetic information from segments of chromosomes.
Chromosomal mutations can result in a disorder within the person. For example, if an individual receives an extra copy of chromosome 21, that individual will develop Down syndrome.
Relationship between mutation and genetic variation:
Some mutations can increase an organism’s chance of survival. An organism that obtains a characteristic by mutation that increases its chances of survival is more likely to live long enough to have offspring. If the offspring then inherits this trait, its chances of survival are also increased. Over a period of time, more of the population will possess this advantageous trait. It is through mutation that organisms have become resistant to the methods humans use to kill them or control the size of their population. Then these organisms live long enough to reproduce and pass on this resistance trait. Over time, more of this specie’s population possesses the trait and the control methods used by humans can no longer be used. Mutation is the only way that variation can occur within asexually reproducing organisms. Asexually reproducing organisms produce clones that are genetically identical unless a mutation occurs. A change or error in the DNA sequence in cell division can provide new alleles. Variation caused by mutation can also benefit sexually reproducing organisms. A mutation may allow a species such as insects to become resistant to pesticides. This resistance trait can then be passed on to their offspring. As more of the population inherit the resistance trait, the control method becomes increasingly ineffective.