How Tall Will My Child Be?
One would think that tall mothers and fathers would produce tall children, or that a short mother would have short daughters even though dad and son are both tall. In either case, the statements do not hold true simply because each person carries dominant and recessive genes that when combined determine how tall or short you may be. We say ‘may be’ because genes are not the only determinants of height, environmental factors also play an important role.
There is no doubt about the importance of genes in influencing how tall or short someone will be. It will not be due to one single gene but many. There will be genes to produce and regulate growth hormones, bone growth, muscle mass and many more.
The first ‘tall’ gene was discovered in 2007. Researchers analysed the DNA of 5,000 white European people and found that one tiny change in the HMGA2 gene had an affect on height. Someone inheriting 2 copies of the ‘tall’ version would grow up to 1 cm taller than a person with 2 ‘short’ versions of the gene. The team also found that inheriting 1 copy of the ‘tall’ version would add 0.5 cm to an individual’s height.
In an interview with the British Broadcasting Corporation (BBC) at the time of the discovery, researcher Dr Tim Frayling of the Peninsula Medical School in Exeter expressed the widely held belief that more genes will be revealed. "Clearly, our results do not explain why one person will be 6ft 5in (195.6cm) and another only 4ft 10in (147.3cm). This is just the first of many that will be found, possibly as many as several hundred."
Then in April 2008 the same team made another startling discovery. They believe that 90% of a person’s final height in life is determined by their genes and reached this conclusion after finding 20 different regions of the genome that can influence height and make a difference of up to 6cm in either direction.
Don’t forget the environment
The importance of the environment in determining someone’s height can clearly be seen in the use of doctors’ growth charts. They are used to pick up any potential problems. For example, if a child starts out on a steady growth pattern that then tapers off or drops considerably, the doctor will begin to look at what is causing the change. Children tend to grow considerably between birth and the age of 2 and then there is a growth spurt during the teenage years.
These points in a person’s growth are where stressors – things like malnutrition, child neglect, abuse, and anything else that threaten a child’s well-being – can impact how they grow. Additionally, exercise, pollution, sleep patterns, climate, fitness, diet, and psychological well-being can also impact growth.
Understanding the genetics and environmental influences on growth will have important benefits for medicine. First of all genetic discoveries may actually help scientists to find treatments and cures for diseases that affect bones, such as osteoarthritis and cancer. It also has the potential to improve our knowledge of many other diseases. In epidemiological studies it’s been shown that short people tend to be more at risk of contracting heart disease and tall people are more at risk of getting bladder and lung cancer. Of course these findings are not absolute but it serves to highlight the complex interrelationships of many of our genes. This is one tall story that really will go on and on and on and ………………