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Did you know that Handedness was a Result of Evolution

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James Cardozo

on 16 March 2017

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Transcript of Did you know that Handedness was a Result of Evolution









There are up to 40 genes that can influence the hand preference of individuals, but 2 have the most significance. The genes of PCSK6 and the LRRTM1. These genes are involved in the left- right symmetry in mammals.





What is handedness?
Single Gene Theory
- Handedness is the liking of a person to a certain hand; left handed, or right handed.

- This is formally known as brain lateralization. The right hand is connected to the left hemisphere of the brain. While the left hand is to the right hemisphere.

I chose this topic because I came across an interesting fact that only 10% of the population are left handed. I knew that there are fewer left- handed people in the world, but not as great as this.


Why I chose this topic
Why does this relate to our unit?
The topic of handedness has always been a problem within the scientific community for it does not rely on just genetical factors. It also has many genes that affect bilateral beings, making it hard to grasp just the facts about LRRTM1 and PCSK6. Not much information can be found about these genes for it has only been a recent discovery. However, as we understand more of this concept, our understanding of how certain biological and psychological functions deepens. The biological knowledge of handedness may also be used to know what really makes up the mentality of a person, aiding in the research of psychology. In addition, these facts can also help in understanding how close we really are to our primitive cousins, apes, and how our genes differentiated from that of other beings. Although this would be of great help, scientists still have their hands full with figuring out the genetics of brain lateralization.
Conclusion
Why are there less left handed people on earth?
Why do we have it?
Genetics
The subject of handedness touches areas of the functions of certain genes in the chromosomal level

How modifications or mistakes during DNA replication can create differences in humans

According to our outline, we will also learn Mendelian understandings of heredity, which was the foundation of Punnet Squares.
PCSK6
LRRTMI1
The gene PCSK6 is a gene that affects the development of the body and organs. Those with the normal gene have equally sized corpus callosum, a band of nerve fibers in the middle of the brain.
This structure makes communication in the brain efficient.
The change in the structure of PCSK6 affects the corpus callosum by making it bigger. Usually, this is seen in left- handed people. Some might also have smaller callosums, causing the brain to have more preference on one side of the brain.

Scientists understood handedness in two ways:
- Caused by a single gene

- Caused by multiple genes, which is the current accepted theory
This theory states that handedness is due to alleles, which are the variations of a gene in a person. There are two types of alleles. A dominant, which shows the trait that it holds whenever it is paired up with anything, and the other are recessive. Recessive alleles only show when it is paired with one another. This concept is described with Punnet Squares.

R = Right Handed r= Left handed
r
r
R
r
Rr
Rr
rr
rr
Multiple Genes
PCSK6
LRRTM1
This gene is associated with how the brain works. Those with the normal LRRTM1 gene, has brains that function perfectly. However, those that have defects to it develop mental illnesses like dyslexia, a reading and language problem.
Left- handed people actually have a modification to this gene similar to dyslexia, but not as severe. The modification instead, makes the travel of signals in the brain to focus on the right side that controls emotion and creativity, rather than it being equal with the left that controls logic and language. Since the right hemisphere controls the left hand, this creates a left handedness.

I also chose this because of its relatability. I am left- handed, so learning about why I am left handed interested me.
Sources:
https://ghr.nlm.nih.gov/primer/traits/handedness

https://www.geneticliteracyproject.org/2016/08/29/left-handedness-genes-and-a-matter-of-chance/

https://www.sciencealert.com/here-s-why-are-some-people-left-handed-according-to-science

http://www.livescience.com/39611-genes-for-handedness-found.html

http://news.nationalgeographic.com/news/2007/08/070801-left-gene.html
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