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A Genetic X-ray

A Genetic X-ray
September 27, 2018 Navya Sahay
Navya Sahay
In Uncategorized

Whether you have blond hair with blue eyes or jet black hair with brown eyes or brown hair with light brown eyes or well, the list goes on…, you all have one thing in common. And that is the fact that all of you look slightly like either your parents, your grandparents or any other relative in your family. Don’t believe me?

  1. Go and look at yourself in the mirror and write down your physical traits. E.g: Tall, short, widow’s peak, free earlobes,etc. A quick fact: If you have a widow’s peak, it doesn’t mean you are a widow. Rather, a widow’s peak is just the upturned ‘V’ shape at your hairline.
  2. Next, compare your traits with all your immediate relatives.
  3. You will realize that you share traits with at least a few of them. You will also realize that although you certainly share some similarities with them, neither of them look exactly like you. Yes, you are unique!

But, why do you share traits with your family members?

Keep your hair on, hold your horses, I shall tell you why. The reason for this is genes. You ask,” Jeans? The cloth?”. No, not the clothes. I meant genes, spelt with a g. Everybody has genes. They are the characteristics passed on to you from your parents. To keep it simple, let’s imagine that your father is tall and your mother is short. And let’s just imagine that your paternal grandparents too are tall, therefore your father has tall characteristics coming in from both sides. Your father is tall, and denoted with a TT: two tall characteristics from both his parents. And your mother is short and is denoted with a tt: two short characteristics from both her parents. Now you wonder. If my father is tall and my mother short, what will I look like? Well the answer is:tall. But then you say, “Hey wait a minute, I inherit a trait from each of my parents. What happened to the short trait from my mother?”. Well, you actually do have a short trait in you. But the thing is, the tall trait is dominant and the short trait is recessive. Hence, although you do carry the short trait, it is seen as the dominant trait overpowers it. So you would have one T from your dad and one t from your mom, making you denotation: Tt. Of course, human traits are usually more complex, but these are the basics.

Genes are the characters in an individual that he/she passes on to his/her offspring. Each character has two or more alleles. Alleles are just a fancy word for traits. For example, height has two variations: tall or short. And these alleles shape your phenotype : the way you look. Your genotype is a little different. Remember in the previous case, you had a tall allele as well as the short one? Only the tall allele shows up in your phenotype as you look tall. Your genotype on the other hand is the tall and short allele. So it may be possible that your own kid would inherit the short allele and if your wife too is short, there is a possibility that your kid too will be short.

As you start to form an idea of genes, you are struck with a problem. How do you visualize them? DNA is the answer to this. It stands for Deoxyribonucleic acid. Complex name, which is why DNA is so much easier. DNA is an acid that is present in your cells. All genetic information is stored in this ladder-like structure. And the genes,the alleles of the genes are all located in this storeroom of genetic information.

Do you have a sibling? If so, why do you not look exactly like him or her? You have the same parents, after all. Yes, so you do have a number of similarities and while each of you inherit 50% of your traits from your mom and the other from your dad, it is statistically impossible for you both to acquire the exact same set of alleles. Hence, you are similar, but not exactly the same. Each of you acquire a different 50% of alleles from your parents.

Now let us delve a little deeper into the field of genetics. You wonder, how can one distinguish a dominant trait from a recessive one. that is all thanks to a smart scientist, long ago, called Gregor Mendel. He discovered the existence of genes and he did so by using pea plants! Looks like your grandmother was right, gardening really does build your character! Mendel used two types of pea plants: the ones with purple flowers and the ones with white flowers. Both the flowers were pure parents. By pure parents, I mean that they both had the same trait from each of their parents. So the purple flowers were: PP and the white ones:pp. Wondering why I don’t call the white ones,”ww”? That is because purple and white are alleles of the same character or gene. Purple is the dominant trait and white is the recessive one. But Mendel didn’t know that. He however had some brain, because he figured it out himself.

He cross pollinated a pure purple flower with a pure white one. Cross pollination is when a plant reproduces with another plant. The offspring of these two very different parents were all purple. This was the first generation and their genotype was one purple allele and one white one, denoted as Pp. Since purple is dominant, most of them were purple. Next, Mendel made the offspring reproduce within themselves. So the mother was Pp and so was the father. Time to take out your maths book. The combinations of genotypes possible in the offspring are: PP, Pp,Pp and pp. The first three will all have purple phenotypes as the allele for purple is dominant. This is why around 75% of the offspring were purple. That mean in every 4 flowers, 3 were purple and 1 was white. This was the second generation. Due to the fact that there were fewer white offspring, Mendel could conclude that they were recessive.