The Structure and Function of DNA - Molecular Biology of the Cell - NCBI Bookshelf
Deoxyribonucleic acid, or DNA is the material that is located in the cell's 1 educator answer; Is the beginning of the gene always found at the beginning of the DNA strand 2 educator answers; How do you calculate the number of neutrons?. Each gene (made of DNA strands) on the chromosome has its own specific location The non-coding DNA has become useful in defining biological relationships and .. The rungs of the ladder are made of 4 things that only connect 2 ways. 2. it is responsible for passing genetic information from one generation to the . 2 . As the two DNA strands unwind in the early stages of the duplication process.
Second the diagram of transcription on those pages is quite dreadful: Simple diagrams are both more honest and intelligible. Maria already said that in her and that is also the way I see it view antisense and template are corresponding. I am not a big fan of the sense vs. However, she uses the term 'template' in the question, so I find it more natural to use that term to help her with her confusion the way I understood it.
To your second point: I think she grasped the process of transcription - therefore I did not really care for the diagrams.
In brief this is because 1. I will add a longer argument about this to my answer when I have a little time. The template can be both of those strands depending on the gene. You are right, however, that one needs to make clear that the copy is a reverse complement and not identical.
DNA function & structure (with diagram) (article) | Khan Academy
Looking forward to your argument. This states what you appear to be already aware of, that: DNA sense strand 3' DNA anti-sense strand template for transcription 5' However the genes in a bacterial DNA do not have the same directionality, so one can and should only talk about the sense strand of the DNA specifying a particular gene. Because only the base differs in each of the four types of subunits, each polynucleotide chain in DNA is analogous to a necklace the backbone strung with four types of beads the four bases A, C, G, and T.
These same symbols A, C, G, and T are also commonly used to denote the four different nucleotides—that is, the bases with their attached sugar and phosphate groups. Figure DNA and its building blocks. DNA is made of four types of nucleotides, which are linked covalently into a polynucleotide chain a DNA strand with a sugar-phosphate backbone from which the bases A, C, G, and T extend. A DNA molecule is composed of two more The way in which the nucleotide subunits are lined together gives a DNA strand a chemical polarity.
The three-dimensional structure of DNA —the double helix —arises from the chemical and structural features of its two polynucleotide chains.
DNA - Wikipedia
Because these two chains are held together by hydrogen bonding between the bases on the different strands, all the bases are on the inside of the double helix, and the sugar -phosphate backbones are on the outside see Figure In each case, a bulkier two-ring base a purine ; see Panelpp.
This complementary base-pairing enables the base pairs to be packed in the energetically most favorable arrangement in the interior of the double helix.
In this arrangement, each base pair is of similar width, thus holding the sugar-phosphate backbones an equal distance apart along the DNA molecule. To maximize the efficiency of base-pair packing, the two sugar-phosphate backbones wind around each other to form a double helix, with one complete turn every ten base pairs Figure Figure Complementary base pairs in the DNA double helix. The shapes and chemical structure of the bases allow hydrogen bonds to form efficiently only between A and T and between G and C, where atoms that are able to form hydrogen bonds see Panelpp.
Figure The DNA double helix. A A space-filling model of 1. Each turn of DNA is made up of The coiling of the two strands around more The members of each base pair can fit together within the double helix only if the two strands of the helix are antiparallel —that is, only if the polarity of one strand is oriented opposite to that of the other strand see Figures and A consequence of these base-pairing requirements is that each strand of a DNA molecule contains a sequence of nucleotides that is exactly complementary to the nucleotide sequence of its partner strand.
The Structure of DNA Provides a Mechanism for Heredity Genes carry biological information that must be copied accurately for transmission to the next generation each time a cell divides to form two daughter cells. Two central biological questions arise from these requirements: The discovery of the structure of the DNA double helix was a landmark in twentieth-century biology because it immediately suggested answers to both questions, thereby resolving at the molecular level the problem of heredity.
DNA structure and function
We discuss briefly the answers to these questions in this sectionand we shall examine them in more detail in subsequent chapters. DNA encodes information through the order, or sequence, of the nucleotides along each strand.
Each base —A, C, T, or G —can be considered as a letter in a four-letter alphabet that spells out biological messages in the chemical structure of the DNA. As we saw in Chapter 1, organisms differ from one another because their respective DNA molecules have different nucleotide sequences and, consequently, carry different biological messages.
But how is the nucleotide alphabet used to make messages, and what do they spell out?
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- The molecular structure of DNA
As discussed above, it was known well before the structure of DNA was determined that genes contain the instructions for producing proteins. The DNA messages must therefore somehow encode proteins Figure This relationship immediately makes the problem easier to understand, because of the chemical character of proteins.
DNA and cell division
As discussed in Chapter 3, the properties of a proteinwhich are responsible for its biological function, are determined by its three-dimensional structure, and its structure is determined in turn by the linear sequence of the amino acids of which it is composed.
The linear sequence of nucleotides in a gene must therefore somehow spell out the linear sequence of amino acids in a protein. The exact correspondence between the four-letter nucleotide alphabet of DNA and the twenty-letter amino acid alphabet of proteins—the genetic code —is not obvious from the DNA structure, and it took over a decade after the discovery of the double helix before it was worked out.
In Chapter 6 we describe this code in detail in the course of elaborating the process, known as gene expressionthrough which a cell translates the nucleotide sequence of a gene into the amino acid sequence of a protein.
Figure The relationship between genetic information carried in DNA and proteins.