Genetics

Hartzell begins by clarifying some misconceptions an anonymous person had about height. She mentions that height is determined by many different parts of our DNA and give us only a achievable maximum height that isn't guaranteed to be reached, because other factors like diet and socioeconomic status affect it as well. Hartzell mentions that race is what us humans differentiate each other physically, but internally, people of different ethnicities (cultural groups) within the same race can have very different genetic make-ups. There might be certain genetic features that a small group of people share ancestrally, but it's also possible that two people of different races have more genetic similarity than two people of the same race. Basically, race is unreliable in determining height.

“Is Height Determined by Genetics?” discusses height in the scope of genetics and DNA rather than nutrition. The article states that scientists have discovered 700+ genes that make up an individual’s height in their DNA structure, and that these genes make up a decent portion of the overall height while nutrition, which is more environmental, is only a small portion. There is mainly a focus on genetics. The article mentions that variations in specific pieces of DNA can cause certain growth disorders and affect height severely. One of the most common is the FGFR3 gene in which a variation can cause achondroplasia, a common type of dwarfism. There is also the ACAN gene, which depending on the rarity of the variant, can have severe effects on bone and cartilage growth, or be very mild in people that are normally very healthy.

The article states that due to there being many different genetic variations, it’s difficult to determine what height a child will reach after they finish growing. Inheriting some variations from their parents might explain the child’s height in relevance to the parents, but not sibling to sibling. Hormones can also play a role, but scientists haven’t fully looked into that area of study yet. There is an acknowledgement near the end of environmental factors that aren’t related to just the genetic make-up of an individual. These can include an individual’s health and socioeconomic status, but also anything that might have happened while developing in the wound, like the mother’s diet and whether she smoked or drank. The writer mentions that improved quality of healthcare and access to better nutrition is the reason why many immigrant families have children growing taller.

This article was published under MedlinePlus, a health information website by the National Library of Medicine. It’s no surprise that the article has no author as this is information given to us by the National Library of Medicine, which is a part of the U.S. federal government who doesn’t normally post an author with the information on their government websites. Some of the information within this article is outdated as the mentioned scientific journals at the end date to a little over a decade, but this information on genetics can still be relevant. I can use this to explain how genetics play a role rather than nutrition and which specific genes are affected and what disorders are caused due to those variations, if the reader is curious.

Lai starts off by comparing how much of our height is due to genetics (60-80%) and how much is due to nutrition (20-40%). Studies done in the U.S., Australia, and many European countries try to determine the heritability (chance to inherit certain genes) by looking at other genetic features that siblings share. White people have quite a high heritability in this case at around 80% in most countries. Lai acknowledges that different ethnic populations can have more variation in heritability considering the vast amounts of environments (climate, diet, lifestyle) they live in and their genetic backgrounds. Heritability was found to be 65% in China and western Africa.

Lai says scientists can use the heritability percentages to calculate how much of someone’s height is due to environment versus genetics and also predict how tall a child will be based on their parent’s height and the average for the population they come from. Supplements can be used to assist some of the setbacks experienced in developing countries where the population might not have as much access to basic nutrients. Lai finally states that this is why heritability is higher in developed countries and lower in developing countries.

Dr. Chao-Qiang Lai is a molecular biologist of the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts, making him quite credible on the matter of height genetics and determination. However, because this is one of the sources found through the cited section of Wikipedia, it is considerably older, written in 2006. As it was kept as a source and still seems to have relevant information, it’s still an article that can be useful. This will help in my research paper because it approaches it in a way that is easy to understand for people that don’t have much insight on the matter. He mentions some easy calculations that make sense without too many numbers that make it confusing.