Blueprint of Life Topic 14: Nature Versus Nurture. Biology in Focus, HSC Course Glenda Childrawi , Margaret Robson and Stephanie Hollis. DOT POINT(s). outline ways in which the environment may affect the expression of a gene in an individual
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
Is an ability to play sport inherited? Why does tightrope walking tend to run in families? Is shyness genetically determined or does the environment in which we grow up influence this? What about intelligence? Why do identical twins separated at birth and later reunited often show unexpected similarities, such as playing the same sport, liking the same foods and even choosing the same profession?
Some variations in organisms are genetically determined (‘nature’), whereas others are influenced by the environment (‘nurture’). However, many variations arise as a result of an interaction between these two—the environment can influence how genes are expressed.
The term ‘nurture’ here refers to a wider influence of the environment than just the nurturing one of the home; it includes all environmental influences.
Many studies have been conducted as a result of the interest of people in the relative role of genes and the environment in determining a person’s physical appearance, behaviour, personality and ability in sport, the arts and many other areas.
Numerous studies have been conducted to determine the influence of genes, the environment or a combination of these on phenotype (the physical appearance), including behaviours and
A variety of studies on both plants and animals show that the effect of a gene can be enhanced or masked by variation in the environment. Some human research has involved twin studies, since identical twins have identical genetic material (genotypes) and so any phenotypic differences between them indicate some influence of the environment.
The coat colour of Siamese cats is determined by a colour mutation. Cats that have the allele C have uniform pigmentation of their fur over all parts of their bodies. However, cats that are homozygous recessive for the mutant allele c have dark pigmentation at the extremities of their bodies—the tips of their ears, tail, legs and face.
These are also the areas of poorer circulation—the last to obtain heat from the blood (think of which parts of your body get cold first in really low temperatures). Pigment can be produced by the allele c only at low temperatures. Other parts of the body are subjected to higher body temperatures and so no dark pigment is produced.
As the cat gets older, it may darken more as its circulation becomes poorer and a greater proportion of each extremity is colder. The phenotypic expression of colour is therefore influenced by the temperature of the environment.
An example of the effect of the environment on plant phenotype is seen in flower colour in hydrangeas. The acidity or alkalinity of the soil influences the colour of the flowers. Hydrangeas growing in acidic soil develop blue flowers, whereas those grown in alkaline soil develop pink flowers.
A simple example of how the environment affects gene expression can be seen in growth of humans. Human height and infant birth weight have a genetic basis, but the lack of nutrients or the presence of toxins (such as those present in cigarette smoke) can restrict growth.
Another well-researched example is that of the disease PKU (phenylketonuria). Early intervention with nutrient supplements can affect gene expression, keeping the symptoms such as mental deficiency and lack of pigment in hair and skin at bay.
-Students to begin Effect of Environment on Phenotype PRAC