A third way that gene duplicates arise is by retrotransposition.

Here the messenger RNA from a gene is reverse-transcribed to DNA, which is then integrated into the genome.

TLS Online TPP Program

#Id: 8276

#Unit 1. Molecules and their Interaction Relevant to Biology

TLS Online TPP Program

#Id: 8277

#Unit 1. Molecules and their Interaction Relevant to Biology

For maximum stability, the donor pair (AH) and the acceptor (B) are usually colinear (that is, i., AHB = 180°), but deviations of up to 30° are known.

TLS Online TPP Program

#Id: 8278

#Unit 1. Molecules and their Interaction Relevant to Biology

Plot of density versus temperature for liquid water.

The maximum density of water is reached at 4°C.

The density of ice at 0°C is 0.9167 g cm-3•

TLS Online TPP Program

#Id: 8279

#Unit 1. Molecules and their Interaction Relevant to Biology

Charge–charge (ionic) interactions

These interactions occur between the side chains of oppositely charged residues as well as between the NH3+ and COO− groups at the ends of polypeptide.

TLS Online TPP Program

#Id: 8280

#Unit 1. Molecules and their Interaction Relevant to Biology

Coulomb’s law describes the potential energy (V) between two separated charges (in a perfect vacuum) according to the relationship.

TLS Online TPP Program

#Id: 8281

#Unit 1. Molecules and their Interaction Relevant to Biology

In absence of water the magnitude of the charge–charge interaction is significantly greater.