Structure of a chromosome

Hi friends,
In this post I am going to talk few things about chromosome because we need a basic understanding of what a chromosome is and what it looks like before we move on to the next post. Chromosomes are nothing but an organized structure of DNA (please refer previous post for more details on DNA) and proteins. In humans, chromosomes are present in two types of DNA - nDNA and mtDNA. nDNA contains 23 pairs of chromosomes whereas the mtDNA contains only one chromosome. Upto this point we covered in the previous post. I just wanted to do a recap so that we would not lose continuity.

Now, let us see the structure of chromosome. Each chromosome contains three basic parts - Arms, Centomere, Telomere. The following figure depicts it.
 


Structure of a chromosome

So, as we see in the above picture, the chromosome contains two arms - one short arm (called p arm) and one long arm (called q arm). The short arm and the long arm are joined together with a region called Centromere. And at the end of the arms present the Telomeres. The function of the telomeres is to prevent the materials present in a chromosome from mixing with the neighbouring chromosome and vice-versa. As we can understand, a chromosome contains ONLY ONE Centromere (in the center) and Telomeres are present ONLY AT THE EDGES of the arms (to server the purpose). Please note that there cannot be more than one centromere and telomeres can be seen only at the edges of the arms. I am stressing this point here because it is going to play a major role in our next post. I am just giving some heads up here in this post. Please dig more to get more information (details) about the chromosomes... THE PATH WILL BE FOLLOWED...

Tracing the humans back to Africa

 

A2

B2

C1 -  D1

H

H5

J

K

L

L3

M

N

R

T1

T2

U

U5a

V

 

Hi friends!
This post is going to be a very important one. This post is going to discuss about our past grilling down to the first humans on this planet, their expasion and migration. To understand this post, we need to have a basic understanding of DNA, genes, haplogroup and stuff like that. These concepts have already been discussed in the previous post for the convenience of our readedrs. So, here we go!

As we discussed already, haplogroups are nothing but the group of closely related people having a common ancestor. For covenience, these haplogroups are given names with the alphabets of English starting from A to Z combined with numerals. So, I believe you would have taken a look at the above photos. They are nothing but the frequency of occurrence of the different haplogroups at different parts of the world. These set of photos are the ones that take us to the root of ourselves - the first humans. Please take a look at the photo captioned L and L3. And you know the haplogroup that is oldest of all? That is the first of the haplogroups? It is nothing but the grand parent of L3 which is L3'4'6. It is around 100,000 years old. So, L3 is the descendant of L3'4'6 which means it is the oldest among the existing haplogroups. And you see which part of the world it is seen in? Yes, it is Africa. So, this proves that first of the humans were seen in Africa and spread to the rest of the world from there. Okay, let us trace the path of this spread. See the photos with Captions A2, B2, C1, D1. These haplogroups as seen from the photo are seen in Americas. The parent to A halogroups is N, parent to B halogroups is R, for C and D halogroups the parent is M. In short, the halogroups A2, B2, C1, D1 are found in Americas and the parent halogroups are M,N,R. So now see the photos with captions M,N and R. These are found in Europe, Asia and parts of Africa (including middle East). So,  people of Americas come from Eurasia (Europe + Asia). Finally the haplogroups T1, T2 and U also share the common ancestor R.
So, careful study of this shows one thing. First humans appeared in Africa. They moved out to Eurasia (Europe + Asia) through Middle East. And finally moved to Americas from Eurpoe. So, this is a very significant post in this blog. This post serves the whole purpose for which this blog was started. But still, I believe there are many things to be explored...THE PATH WILL BE FOLLOWED.

Hi friends!
How many of us know about DNA? I believe most of us know about it. But still, if there is anyone out there who doesn't know about it or would like to know more about it, this post be useful. The knowledge about DNA is important at this point of time. Because, our next post is going to talk about the most important topic based on the DNA. It is going to be so much important that it is going to show us apparently the path of our history - The ultimate goal of this blog!

DNA stands for DeOxyRibo Nucleic Acid. It is the acid that contains genetic information of a living being. There is only one group of organisms in the world that doesn't have DNA - RNA Virus. Apart from this, all the living organisms have got DNA. It is present in a cell. Within cell, it is seen in two regions, one being called 'Nucleus' and the other being called 'Mitochondria'. Based on this, we could classify the DNA into two types - nDNA (found in nucleus) and mtDNA (Mitochondrial DNA).
There are many information to know about DNA. But, they are out of scope of this blog, the inclusion of which will make this blog a Science blog rather than a History blog. So, we shall stand within our bounds. Also, we shall restrict ourselves to human DNA as that is what is needed.

nDNA:
Human nDNA contains 46 chromosomes out of which 23 come from the biological father and 23 come from biological mother. These 46 chromosomes are responsible for various charateristics and behaviours of a human. Out of the 46, 2 chromosomes are responsible in determining the sex of a human. They are called Xand Y chromosomes. A human female contains 2 chromosomes(XX) for sex determination and a human male contains 2 chromosomes(XY) for sex determination. During reproduction, a male will contribute a sex chromosome (Could be X or Y since he has got XY) and a female will contribute a sex chromosome (could be only X since she has got XX). If the male
contributes X, then the child will have X from father and X from mother making it to have XX to become a female child. If father contributes Y, then the child will have Y from father and X from mother making it to have XY to become a male child. And all of these 46 chromosomes during reproduction (cell division) will mix and fuse and can result in any combination. This is the story and significance of nDNA.

mtDNA:
Against the 46 chromosomes present in an nDNA, there is only one chromosome present in mtDNA. The most important feature of this DNA is that it is inherited only through mother. i.e. Both male and female will possess this but only the female will pass on this mtDNA to the child. e.g. a couple have got 2 male children. It means that the mother would have passed mtDNA to her 2 male children. But, neither of the 2 male children will pass on this mtDNA to their children.

Mutation:
Mutations are the accidental changes that happen to the DNA. e.g. A is a DNA. A small change of a may happen to it to make it Aa and a change of b may happen to it to make it Ab and so on. So, the DNA 'A' becomes the ancestor DNA for DNAs like Aa, Ab.

Haplogroup:
It is a group of people who share a specific mutation or mutation series that link them to the common ancestor. So, consider that we find a DNA with a Y chromosome with mutation (change) y. If we remove the change (mutation) y, we would get the details of the original DNA with Y chromosome. In some cases like this,it is a single change to be removed. But in many cases, there will series of changes to be removed to get the original one.
As in our previous example under 'Mutation', the DNA with chromosome called A becomes the ancestor and all the other mutated ones like Aa, Ab form a haplogroup. Our world population has got many such haplogroups which would map to a common ancestor. This is the whole root that we have to understand before we move on to the next post.
I am not posting the actual study in this post to allow the viewers to have some time understand the basics of the DNA and all the stuff explained here, to make their own study by googling or any such way to make themselves stand in a better position in this subject before going through the actual study that is going to follow this.
...THE PATH WILL BE FOLLOWED...

What would have been population of India in early days?

Hi friends! Any idea on what would be the population or size of India in early days - may be in or around the days of Mahabharatha? We cannot be sure, but still we can make a rough comparison based on the army size. Yes, please continue reading. In Mahabharatha, there is a sloka (verse) that explains the strength of Pandava and Kaurava armies that took part in Kurukshetra. The sloka is highlighted in the photo. Here is the English Translation of the sloka:

Kashtam Yudhdhae dhasha shaeshaa: shrutha mae thrayoasmaakam Paandavaanaam cha saptha
Dhvyoonaa vimsathiraahathaadhouhineenaam thasminsangraamae vigrahae dhathriyaanaam
It means: The difficult war has left only ten alive - three from our side (Kaurava) and the Pandavas seven, in that dreadful conflict eighteen Akshauhinis of Kshatriyas have been slain!

So wondering where is the strength of army mentioned? I believe not. Because, I have highlighted it as well. Yes it is "Eighteen Akshauhini". It is the keyword. One Akshauhini comprises of the following:
21,870 Chariots
21,870 Elephants
65,610 Cavalry (Horses)
109,350 Infantry (Soldiers on foot)
So, the total strength of one Akshauhini is 218700. So, 18 times 218700 gives us 3936600. Could you believe it? It is almost 4 million. This 4 million is split into 1530900 (7 Akshauhini) on Pandavas' side, 2405700 (11 Akshauhini) on Kauravas' side. Let us compare this strength with strength of Indian army at present. The Indian army at present has 1,129,900 active personnels and 960,000 reserved personnels, 2089900 in total which is nothing but 2 million. Today we have got a population of over 12 billion and today we have got all the complex forms of terrorisms and neighborhood threats. So, if 12 billion population has got an army strength of 2 million, what amount of populatio would have got an army strength of 4 million. This gives us two indications. One is the population. The other important indication is the boundary of India. What size of a country could have occupied such a size of people?!!! There are other slokas in Mahabharatha that talks about this 18 Akshauhini. But the reason for me selecting this sloka is that this particular sloka has got a treasure of information in it. It is "eighteen Akshauhinis of Kshatriyas have been slain". So, at the end of this war 4 million people have died which means a great reduction in population!!!...THE PATH WILL BE FOLLOWED...

Guess what this text could be! In fact it could be found from the image itself. Yes, it is Mahabharatha - Mausala Parva, Adhyaaya 8, Sloka 40 (highlighted in red box). Getting what it is? Here is the English translation of this verse:

Niyathi thu Janae thasminsaagaro makaraalaya:Dhwaarakaam ranthasampoornam jalaenaaplaavayaththadhaa

And here is the core meaning of this sloka:
It is indeed the destiny of people to go into water as the city of Dhwaraka will be completely submerged under the ocean.

On May 19, 2001, India's science and technology minister Murli Manohar Joshi announced the finding of ruins in the Gulf of Khambhat. The ruins, known as the Gulf of Khambhat Cultural Complex (GKCC), are located on the seabed of a nine-kilometer stretch off the coast of Gujarat province at a depth of about 40 m. The site was discovered by a team from the National Institute of Ocean Technology (NIOT) in December 2000 and investigated for six months with acoustic techniques. A follow up investigation was conducted by the same institute in November 2001, which included dredging to recover artifacts. A round of further underwater explorations was made in the Gulf of Khambhat site by the NIOT team from 2003 to 2004, and the samples obtained of what was presumed to be pottery were sent to laboratories in Oxford, UK and Hannover, Germany, as well as several institutions within India. And it is proved that the artifacts could be dated back to 2500 BC to 1400 AD. So, it is not that Mahabharatha is just a story. It could tell us a great history of an important part of the world called India if we read it carefully!... THE PATH WILL BE FOLLOWED...

Welcome!

Dear visitor,

Welcome! The very purpose of this blog is to study the history of the world as much finer as possible crossing the geographical, linguistic and religious borders. One suggestion from my side is that we can use the so called religious books or records namely the Bible, Quran, Hindu literatures like Vedas, Puranas, Ithihasas and x, y, z as history books. These works contains great amount of information about the past which were once the past's present! Not only these, there are lots of Tamil literary works like Pathu paattu, Ettu thogai, pathinen keel kanakku, pathinen mael kanakku, Thirukkural etc., These contain a wealth of information about the past. My motive is to study whatever we can and get as much information as possible and share it. I hope you gain something out of this blog. Enjoy!

Thank you,

Ragavendran B.