1 For example, the disorder sickle cell anaemia is caused by a mutation in the gene that instructs the building of a protein called haemoglobin. 2  This causes the red blood cells to become an abnormal, rigid, sickle shape. 3  However, in African populations, having this mutation also protects against malaria.
Optimistic time - generally the shortest time in which the activity can be completed. It is common practice to specify optimistic times to be three standard deviations from the mean so that there is approximately a 1% chance that the activity will be completed within the optimistic time.
Answer: This is the shortest day of the year, meaning the one in which we experience the least amount of daylight in 24 hours; it is also the time when the Sun reaches its southernmost point in the sky. Although this part of Earth is cooling, its great thermal mass still retains some heat from the summer and fall.