Question

What are some unique characteristics of human brains, relative to other vertebrates? Identify three genetic changes in humans lead to these differences. What is the mechanism for each.

Answer 1

Some unique characteristics of human brain relative to other vertebrates are:

• rapid increase in brain size
• Increase in structural complexity
• Advanced cognitive capacity

Genetic changes and mechanisms that led to these changes are broadly divided into 3 categories:

(i) positive selection on protein-coding regions of the genome that lead to changes in the sequences of existing proteins;

(ii) duplication and deletion of genes; and

(iii) evolutionary changes in non-coding regions of the genome, especially those in cis-regulatory sequences that lead to altered gene expression.

Figure :- Schema of several types of evolutionary changes in a gene that could potentially contribute to human brain evolution.

The genetic changes that potentially underlie human brain evolution span a wide range from single nucleotide substitutions to large-scale structural alterations of the genome.

Similarly, the functional consequences of these genetic changes vary greatly, including protein-sequence alterations, cis-regulatory changes and even the emergence of new genes and the extinction of existing ones.

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