The answer is; the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer
In Africa, due to its equatorial latitude location, receives direct sunlight at more or less 90 degrees most of the year. These highly concentrated rays increase the UV radiation exposure that can cause damage to cell DNA. Selection pressure, therefore, favored individuals with high melanin concentrations that protect against UV. Therefore population evolved towards high melanin densities in the skin.
Why is the active site specific for only one type of substrate? Enzymes have a lock and key type fit so only a specific substrate fits in the activation site.
Ans. (4). protein synthesis.
Protein synthesis can be defined as a process that involves formation of polypeptides or proteins by using information present in DNA. It is divided into two steps, transcription and translation.
During transcription, DNA is transcribed into mRNA and information present in DNA is transferred to mRNA as codons. Codons represent triplet of nucleotides and each codon codes for a specific codon.
Translation involves formation of protein, during which amino acids are added to the growing polypeptide chain with the help of codons.
The given diagram represents process of translation. Thus, the correct answer is option (4).
