Question

What is the assumption behind the comparison of DNA sequences to deduce that two individuals, or two species, are related?

Short answer

The key assumption behind the comparison of DNA sequences to determine relatedness between two individuals or species is that similar DNA sequences indicate a recent common ancestor.

Step-by-step solution

Understanding the basic concept

In genetics, DNA sequences of individuals or species are compared in order to deduce relatedness. It is based on the concept of 'common ancestry' and the principle that 'more closely-related organisms share more similar DNA'.

Explanation of the Key Assumption

The key assumption behind the comparison of DNA sequences is that if two individuals or species show high similarity in their DNA sequences, it indicates that they have a common ancestor. This is because DNA is passed from parent to offspring, and over generations, small changes (mutations) occur. Hence, organisms that have diverged more recently will have accumulated fewer differences in their DNA sequences, showing greater similarity.

Beyond the assumption

It's also crucial to understand that this comparison is statistical, meaning that it is based on probability. The greater the sequence similarity, the higher the likelihood of recent common ancestry. However, identical sequences do not necessarily indicate immediate kinship, as convergent evolution or horizontal gene transfer (especially in microorganisms) could also lead to similar sequences.