Question

1. After birth, the environment may exert either a positive or negative effect on growth.

   True

   False

  

1. Twins can be labelled as either "monozygotic" (developed from the same egg) or "dyzogotic" (developed from two independent eggs). The difference in height of monozygotic twins is probably caused by environmental factors.

   True

   False

1. Body proportions are probably not under genetic control during the growth process.

   True

   False

Answer 1

1. TRUE - After birth, the environment may exert either a positive or negative effect on growth. ... Urbanization also has a positive effect on growth. Over the past 100 years, the study of environmental influences on human physical growth and development has focused on the influences of social and economic factors; family and household characteristics; urbanization/modernization; nutrition; and features of the physical environment such as altitude, temperature and climate. Continuing in this tradition are current investigations into the roles of pollutants and other aspects of the human-made environment in affecting patterns of human growth and development, specifically the timing of sexual maturation and the development of obesity.

2. TRUE - Although the majority of monozygotic twin pairs achieve an identical height, a proportion of them are discordant. Because monozygotic twins completely share their genome, differences in their adult height are not due to heritable factors. Some identical twins can have different heights and weights. This is because height and weight are controlled by what you eat as well your DNA. Differences in diet can start earlier than you might imagine. When the twins are growing inside the uterus, there can be differences in how well they connect to the placenta.Monozygotic twins in an economically developed society share early socioeconomic status and common access to the same food supply. They adopt a more similar diet than dizygotic twins, even when raised apart, implying a heritable component to caloric intake. Thus, differences in height are likely to be at least partially determined by unique personal experiences such as illness, including infections.

3. TRUE - The data are, however, circumstantial as no genetic basis for body shape is provided in any of the studies cited. Indeed, there is no known basis for the determination of human body proportions.We find that population differences in body proportions are influenced very little by genetic background, at least as imputed from geographic, ethnic, or "racial" categorisations.