Just a query about how DNA works?

Question

Considering that the human starts off from 1 single cell, which then multiplies out , where does all that information on how the rest of the cells should be created come from . I presume it's in the DNA , a sort of a chemical compiler / assembler which tells the cell on how it should multiply. But even if it has information about all the different cells in the body , how does it know which ones to build next. I find it incredible and incomprehensible that a single cell can grow into an intelligent human being .

Answer 1

It's called developmental biology.

That single cell contains all 46 chromosomes, and based on chemical signals received in the early weeks of life, certain sets of genes are turned on and off in a specified sequence (far too elaborate to squeeze into one Yahoo answer).

There is a great textbook by Sinauer and Associates (Scott Gilbert is the editor) which provides a great introduction and overview of developmental genetics, and it is widely used in North American Universities.

Answer 2

Most cell differentiation isn't actually encoded into the DNA, but is a response to factors from outside the cell. When the embryo is still just a ball of cells, some cells will start releasing growth factors. Say, for simplicity, that there are two growth factors (there are really many, many more), A and B. A cell on one end of the embryo starts secreting A, and one on the other end starts secreting B. Cells that get a lot of A (closest to the A end) will turn into, say, muscles. Cells that get a lot of B (closest to the B end) will turn into nerves. Cells that get a mixture of the two will turn into bone cells. It's a very sensitive process, meaning that cells that get lots of A and a little B will be different than a 50/50 mix or lots of B and a little A. Of course, it's a lot more complicated in real life, since there are so many growth factors and cell types, and the embryo is a complicated 3d form, but the basic concept is the same.

Furthermore, a great deal of organizing is done by folding and physical rearrangement. An embryo begins as a sheet, that then forms a tube, then starts to fold (for example, one end of the tube contains stem cells that are destined to become the brain).

This development is done in stages. The original cells in the embryo are totipotent, meaning that they can (with the proper signals) differentiate into any cell type. Over time, however, they differentiate into multipotent cells. These are cells that have been committed down one particular road of development. For example ectodermal cells (the outer layer of cells in an early embryo) can differentiate into skin, nails, parts of the eye, and the nervous system (since it folds inward during development). They can't, however, turn into muscles. They've lost some of their potential.

In the end, human development isn't directly encoded into the DNA of each cell involved. It is rather a complex system involving signalling between cells, step-by-step differentiation, and physical rearrangement. DNA is still very much involved, but once development is underway, it is no longer the driving force.

Answer 3

That's because God designed it and we human beings proud ourselves of barely discovering the inner works of His creation.

You don't need to understand it. It happens.

Answer 4

Deoxyribonucleic acid, or DNA, is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms. The main role of DNA molecules is the long-term storage of information and DNA is often compared to a set of blueprints, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.

Chemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate atoms joined by ester bonds. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes.

Within cells, DNA is organized into structures called chromosomes and the set of chromosomes within a cell make up a genome. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed
DNA is a long polymer made from repeating units called nucleotides.[1][2] The DNA chain is 22 to 26 Ångströms wide (2.2 to 2.6 nanometres), and one nucleotide unit is 3.3 Ångstroms (0.33 nanometres) long.[3] Although each individual repeating unit is very small, DNA polymers can be enormous molecules containing millions of nucleotides. For instance, the largest human chromosome, chromosome number 1, is 220 million base pairs long.[4]

In living organisms, DNA does not usually exist as a single molecule, but instead as a tightly-associated pair of molecules.[5][6] These two long strands entwine like vines, in the shape of a double helix. The nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together, and a base, which interacts with the other DNA strand in the helix. In general, a base linked to a sugar is called a nucleoside and a base linked to a sugar and one or more phosphate groups is called a nucleotide. If multiple nucleotides are linked together, as in DNA, this polymer is referred to as a polynucleotide.[7]

The backbone of the DNA strand is made from alternating phosphate and sugar residues.[8] The sugar in DNA is 2-deoxyribose, which is a pentose (five carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These asymmetric bonds mean a strand of DNA has a direction. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand. This arrangement of DNA strands is called antiparallel. The asymmetric ends of DNA strands are referred to as the 5′ (five prime) and 3′ (three prime) ends. One of the major differences between DNA and RNA is the sugar, with 2-deoxyribose being replaced by the alternative pentose sugar ribose in RNA.[6]

The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). These four bases are shown below and are attached to the sugar/phosphate to form the complete nucleotide, as shown for adenosine monophosphate.

These bases are classified into two types; adenine and guanine are fused five- and six-membered heterocyclic compounds called purines, while cytosine and thymine are six-membered rings called pyrimidines.[6] A fifth pyrimidine base, called uracil (U), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. Uracil is not usually found in DNA, occurring only as a breakdown product of cytosine, but a very rare exception to this rule is a bacterial virus called PBS1 that contains uracil in its DNA.[9] In contrast, following synthesis of certain RNA molecules, a significant number of the uracils are converted to thymines by the enzymatic addition of the missing methyl group. This occurs mostly on structural and enzymatic RNAs like transfer RNAs and ribosomal RNA.[10]