Mutations
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Mutations. Mutations. In biology, a mutation is a change in the organism’s DNA. There are different types of mutations that we need to understand.

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Mutations1
Mutations

  • In biology, a mutation is a change in the organism’s DNA. There are different types of mutations that we need to understand.

  • A point mutation is one in which one nucleotide is substituted for another. An incorrect nucleotide is put in the place of the correct one. Usually, this mistake is caught and fixed by the DNA polymerase. If it isn’t, the substitution may permanently change an organism’s DNA.



Mutations2
Mutations

  • Another type of mutation is the frameshiftmutation. This involves the insertion or deletion of a nucleotide in the DNA sequence. They shift the entire sequence following them by one or more nucleotides.


Example of a frameshift mutation
Example of a Frameshift Mutation


Check for understanding
Check for Understanding

  • Would a frameshift mutation have a greater effect if it occurred near the promoter or near the end of the gene? Explain your answer.

  • Does a point mutation always change the amino acid sequence of the encoded polypeptide? Why or why not?


Chromosomal mutations
Chromosomal Mutations

  • Gene duplication is one type of chromosomal mutation. This occurs when similar chromosomes exchange DNA segments. If they do not align properly, the segments may be different in size and one chromosomes may have two copies while the other chromosome may have no copy at all.


Chromosomal mutations1
Chromosomal Mutations

  • Gene translocation is another type of chromosomal mutation. A piece of one chromosome moves to a non-similar chromosome. The two chromosomes exchange segments with each other.


Mutation impact on organisms
Mutation Impact on Organisms

  • Chromosomal mutation affects a lot of genes and tend to have a big effect on an organism.

  • Gene mutations can also have a big effect on an organism even though it is smaller in size. Changing one codon may result in a protein that is not compatible with the enzyme and destroy the proteins function.

  • If a mutation occurs in a body cell, then the mutation only impacts the individual organism.


Mutation impact on organisms1
Mutation Impact on Organisms

  • If the mutation occurs in germ cells, the mutation may be passed on to offspring. The mutation in the germ line affect the phenotype of offspring. This may be a positive mutation or a negative one.

  • This is the basis for natural selection.


What causes mutations
What Causes Mutations?

  • Replication Errors: DNA polymerase has a built-in proofreading function to help with replication. However, errors occur and are not fixed over time. Eventually, they impact how the cell functions…. An example of this is aging.

  • Mutagens: Agents in the environment that change DNA. They can break DNA segments or speed up the rate of replication errors. These mutagens can be naturally found (UV light) or manmade (industrial chemicals).


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