Transversion

Definition

A transversion is a specific type of nucleotide substitution where a purine is replaced by a pyrimidine or vice versa. This contrasts with transitions, which involve the replacement of one purine with another purine or one pyrimidine with another pyrimidine. Understanding transversions is crucial in evaluating genetic variations and their effects on protein coding sequences.

5 Must Know Facts For Your Next Test

1. Transversions are less common than transitions, occurring at a lower frequency in many organisms' DNA.
2. Because transversions involve a larger change in chemical structure, they can have more significant impacts on the resulting protein than transitions.
3. In nucleotide substitution models, transversions are often weighted differently than transitions due to their differing probabilities of occurrence.
4. Transversions can lead to amino acid substitutions that may alter protein function, potentially impacting an organism's phenotype.
5. Certain environmental factors, like chemical exposure or radiation, can increase the likelihood of transversions occurring in DNA.

Review Questions

• Compare and contrast transversions and transitions in terms of their definitions and biological implications.
  • Transversions and transitions are both types of nucleotide substitutions but differ fundamentally in their mechanics. A transversion involves the replacement of a purine with a pyrimidine or vice versa, while a transition involves swapping one purine for another or one pyrimidine for another. Transversions tend to be less frequent and may have greater biological implications because they can cause larger structural changes in the resulting proteins, potentially affecting their function and stability.
• Discuss how transversions could influence the process of protein synthesis and the resulting phenotype of an organism.
  • Transversions can lead to changes in codons during protein synthesis by altering the nucleotide sequence. When a codon is changed due to a transversion, it may encode a different amino acid, potentially leading to structural and functional changes in the protein. If these changes disrupt the protein's function, it could result in observable differences in an organism's phenotype, affecting traits like enzyme activity or structural integrity.
• Evaluate the potential impact of environmental factors on the rate of transversions and their evolutionary significance.
  • Environmental factors such as exposure to mutagens like chemicals or radiation can elevate the rate of transversions by causing damage to DNA. This increased mutation rate can lead to greater genetic diversity within populations, which may have evolutionary significance. If certain transversions confer advantageous traits under specific environmental conditions, they could contribute to natural selection and the adaptation of species over time. Consequently, understanding how these factors influence mutation rates helps illuminate the broader mechanisms driving evolution.

Related terms

Transition:

A transition is a nucleotide substitution that occurs when a purine replaces another purine or a pyrimidine replaces another pyrimidine.

Mutation: A mutation is a change in the nucleotide sequence of an organism's DNA, which can lead to alterations in gene function or expression.

Codon: A codon is a sequence of three nucleotides that corresponds to a specific amino acid or signals the termination of protein synthesis.