point mutation is the type of mutation which occur due to change in number of chromosome nucleaotide sequence od gene chromaosome as a whole arrangment of gene

point mutation is the type of mutation which occur due to change in
  1. number of chromosome
  2. nucleaotide sequence od gene
  3. chromaosome as a whole
  4. arrangment of gene


2 Answers

askIITians Faculty 164 Points
8 years ago
Hello Student
Correct answer is 2) Nucleotide sequence of Gene
As when heritable alteration occurs in a very small segment of DNA means single nuleotice or neuleotide pair this type od mutation is called point mutation.
This mutation leads to the change in nucleotide sequence of a Gene.
Raheema Javed
156 Points
8 years ago
The correct answer is 2. nucleotide sequence of gene.
A point mutation, or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA. The term point mutation also includes insertions or deletions of a single base pair.

Transition/Transversion categorization

In 1959 Ernst Freese coined the terms "transitions" or "transversions" to categorize different types of point mutations.
  • Transitions: replacement of a purine base with another purine or replacement of a pyrimidine with another pyrimidine
  • Transversions: replacement of a purine with a pyrimidine or vice versa.
Functional categorization
  • Nonsense mutations: Code for a stop, which can truncate the protein. A nonsense mutation converts an amino acid codon into a termination codon. This causes the protein to be shortened because of the stop codon interrupting its normal code. How much of the protein is lost determines whether or not the protein is still functional.
  • Missense mutations: Code for a different amino acid. A missense mutation changes a codon so that a different protein is created, a non-synonymous change.
  • Conservative mutations: Result in an amino acid change. However, the properties of the amino acid remain the same (e.g., hydrophobic, hydrophilic, etc.). At times, a change to one Amino acid in the protein is not detrimental to the organism as a whole. Most proteins can withstand one or two point mutations before their function changes.
  • Non-conservative mutations: Result in an amino acid change that has different properties than the wild type. The protein may lose its function, which can result in a disease in the organism. For example, sickle-cell disease is caused by a single point mutation (a missense mutation) in the beta-hemoglobin gene that converts a GAG codon into GUG, which encodes the amino acid valine rather than glutamic acid. The protein may also exhibit a "gain of function" or become activated, such is the case with the mutation changing a valine to glutamic acid in the braf gene; this leads to an activation of the RAF protein which causes unlimited proliferative signalling in cancer cells.These are both examples of a non-conservative (missense) mutation.
  • Silent mutations: Code for the same amino acid. A silent mutation has no effect on the functioning of the protein. A single nucleotide can change, but the new codon specifies the same amino acid, resulting in an unmutated protein. This type of change is called synonymous change, since the old and new codon code for the same amino acid. This is possible because 64 codons specify only 20 amino acids. Different codons can lead to differential protein expression levels, however.
Use of term to describe single base pair insertions and deletions
Sometimes the term point mutation is used to describe insertions or deletions of a single base pair (which has more of an adverse effect on the synthesized protein due to the nucleotides' still being read in triplets, but in different frames: a mutation called a frameshift mutation)

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