that similarities in design between different animals prove a common Creator instead of a common ansestor?
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CF has always been a site that welcomes people from different backgrounds and beliefs to participate in discussion and even debate. That is the nature of its ministry. In view of recent events emotions are running very high. We need to remind people of some basic principles in debating on this site. We need to be civil when we express differences in opinion. No personal attacks. Avoid you, your statements. Don't characterize an entire political party with comparisons to Fascism or Communism or other extreme movements that committed atrocities. CF is not the place for broad brush or blanket statements about groups and political parties. Put the broad brushes and blankets away when you come to CF, better yet, put them in the incinerator. Debate had no place for them. We need to remember that people that commit acts of violence represent themselves or a small extreme faction.
Is it possible...
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MSBS
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Well look at it this way, you probably accept genetic sequence homology as proof of relatedness. Do a paternity test, and, based on sequence homology, you can say "this baby is related to that man." No problem so far, right? Go back another generation...larger differences but you can still tell who is related to who. Keep going....it still works, you'll still buy it.....until at some point *poof* you draw a line and say after this it's common design and not common anscestry. Why?
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How does an expert know a perticular painter produced a work of art. Style, brush stroke, use of colour ect. So yes, all living things bear the mark of our designer and creator.
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the problem is that non-functional sequences are shared too, both humans and chimps have inactivated genes
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Late_Cretaceous
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Why then are the marsupial mouse and the blind-marsupial mole of australia more closely related (or designed if you like) to wallabies and tasmanian devils then to their ecological counterparts (mice and moles) in the rest of the world?
Why is it that birds that fill the ecological niches of woodpeckers and parrots in the Galapagos islands more closely related/designed to finches then to actual parrots and woodpeckers? THe same can be asked of honeycreepers in Hawaii.
Why is it that birds that fill the ecological niches of woodpeckers and parrots in the Galapagos islands more closely related/designed to finches then to actual parrots and woodpeckers? THe same can be asked of honeycreepers in Hawaii.
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No. Why would he codge together the panda's thumb, when he had a perfectly workable design in humans?
Frankly, if we're designed, we should sue God.
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Defender of the Faith 777
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I'm having trouble understanding DNA. Someone give us a science lesson on the 5 Carbon sugar, phosphate, and nitrogenous base, and how they all chain together into a double helix to create information. I never did understand it all.
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Try reading Blameless in Abaddon.
God gets sued for crimes against humanity.
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paulewog
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Sue? What for? We are very well designed.
The foot is a regular little bridge. All your weight is supported by your foot, which is an arch shape, and it also keeps amazing balance. Very well designed.
There are similarities in a lot of things. I mean, come on, all land animals BREATHE! they all have lungs. Does that mean they all evolved?
The foot is a regular little bridge. All your weight is supported by your foot, which is an arch shape, and it also keeps amazing balance. Very well designed.
There are similarities in a lot of things. I mean, come on, all land animals BREATHE! they all have lungs. Does that mean they all evolved?
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You don't know much about the human body, do you? We are not, in fact, well designed.
At the very least, it'd be nice to be able to make our own Vitamin C. The gene is there, after all. Just turned off. Our knees need a redesign, our spine isn't the best design for an upright stance (or sitting, for that matter), and our coccyx should be removed. It wouldn't hurt to remove the blindspot in our eyes, and clean up our fetal development.
Why do we make gill arches again?
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Originally posted by paulewog
There are similarities in a lot of things. I mean, come on, all land animals BREATHE! they all have lungs. Does that mean they all evolved?
Why, yes. Yes, they did.
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Unless you've come up with a good way to differentiate the two, I'd say no. If you want to call the processes of the universe "Creator," or claim that those processes are the result of the actions of some entity "Creator," then according to the theory of evolution, both would be true.
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DNAunion: Id be glad to. I dont know if it should be done in this thread or in a new thread though. Ill start here and if it needs to be moved we can.
Here is some stuff from my personal notes:
Nucleotides
The nucleotides involved in nucleic acid polymerization are organic molecules that share a particular arrangement of atoms, with each nucleotide consisting of the following:
(1) A nitrogenous base (A, C, G, and one other U in RNA and T in DNA)
(2) A 5-carbon sugar (ribose in RNA and deoxyribose in DNA)
(3) A phosphate group (PO42-)
The nitrogenous bases are divided into two separate classifications purines and pyrimidines based upon their structure. The double-ringed (bicyclic) purines are adenine (A), and guanine (G). The single-ringed (monocyclic) pyrimidines are cytosine (C) and either thymine (T) or uracil (U), depending upon whether the nucleic acid is DNA or RNA respectively.
The 5-carbon sugars (more technically known as pentoses) found in nucleic acids are virtually identical. The structural difference is that ribose has a hydroxyl group (-OH) on its second carbon whereas deoxyribose has only a hydrogen atom (deoxyribose has been deoxyed at its second carbon - the oxygen that ribose possesses there has been removed by an enzyme).
When a nitrogenous base and an appropriate pentose (5-carbon sugar) are bonded correctly, the molecule is called a nucleoside (notice, nucleoside, not nucleotide). To a nucleoside, either one, two, or three phosphate groups can be attached, resulting in a nucleoside monophosphate, a nucleoside diphosphate, or a nucleoside triphosphate, respectively. The term nucleotide is synonymous with nucleoside monophosphate.
The free energy liberated by the hydrolysis (splitting of a molecule by the addition of water) of one or both of the terminal phosphate groups from the nucleoside triphosphate ATP (adenosine triphosphate) has the ability to drive unfavorable chemical reactions. ATP is the energy currency of cells: it has three terminal phosphate groups and is used as an energy intermediary. ATP couples energy-yielding reactions (which can form ATP by providing the energy needed to add a phosphate group to ADP) with energy-requiring reactions (which can hydrolyze the terminal phosphate of ATP to release energy, resulting in the production of ADP as a byproduct; or can hydrolyze both of the terminal phosphate groups of ATP forming AMP). In fact, the incorporation of nucleotides into DNA or RNA relies on this energy-releasing ability of nucleoside triphosphates, as explained in a minute.
more...
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DNAunion: more from my personal notes:
Nucleic Acids
As stated earlier, the building blocks of nucleic acids are nucleotides. The bonding together of nucleotides can result in a dinucleotide (two), an oligonucleotide (a small number), or a polynucleotide (many), depending upon the number of monomers in the chain. A nucleic acid can be defined as a non-branched, linear series of many nucleotides linked together by phosphodiester bonds.
The process of creating a nucleic acid molecule by adding monomers one at a time to a growing chain is called polymerization, and is catalyzed by proteins known as polymerases. This process consumes energy and is driven, as suggested earlier, by the hydrolysis of terminal phosphate groups from the incoming nucleoside triphosphates (NTPs). Before a nucleotide is incorporated into a growing nucleic acid chain, it exists as a nucleoside triphosphate. The hydrolysis of the two terminal phosphate groups provides the energy necessary to incorporate the nucleotide into the chain, and as a result, the NTP molecule is truncated from a nucleoside triphosphate to a nucleoside monophosphate (which as mentioned earlier, is also called a nucleotide).
A nucleic acid strand has a backbone composed of identical, repeating units a phosphate group is bonded to a pentose, and that pentose is bonded to another phosphate group, which is bonded to another pentose, etc.. Since there is no irregularity in the sequence of symbols that comprise the backbone, it is obvious that it cannot communicate any meaningful amount of biological information. Concerning nucleic acids, only the nitrogenous bases can store and transmit information, because only they contain variation within their symbol sequences. This explains why scientists discussing DNA sequences mention only the bases (A, C, G, and T).
Nucleic acids are divided into two main types RNA (ribonucleic acid) and DNA (deoxyribonucleic acid).
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Nucleic Acids
As stated earlier, the building blocks of nucleic acids are nucleotides. The bonding together of nucleotides can result in a dinucleotide (two), an oligonucleotide (a small number), or a polynucleotide (many), depending upon the number of monomers in the chain. A nucleic acid can be defined as a non-branched, linear series of many nucleotides linked together by phosphodiester bonds.
The process of creating a nucleic acid molecule by adding monomers one at a time to a growing chain is called polymerization, and is catalyzed by proteins known as polymerases. This process consumes energy and is driven, as suggested earlier, by the hydrolysis of terminal phosphate groups from the incoming nucleoside triphosphates (NTPs). Before a nucleotide is incorporated into a growing nucleic acid chain, it exists as a nucleoside triphosphate. The hydrolysis of the two terminal phosphate groups provides the energy necessary to incorporate the nucleotide into the chain, and as a result, the NTP molecule is truncated from a nucleoside triphosphate to a nucleoside monophosphate (which as mentioned earlier, is also called a nucleotide).
A nucleic acid strand has a backbone composed of identical, repeating units a phosphate group is bonded to a pentose, and that pentose is bonded to another phosphate group, which is bonded to another pentose, etc.. Since there is no irregularity in the sequence of symbols that comprise the backbone, it is obvious that it cannot communicate any meaningful amount of biological information. Concerning nucleic acids, only the nitrogenous bases can store and transmit information, because only they contain variation within their symbol sequences. This explains why scientists discussing DNA sequences mention only the bases (A, C, G, and T).
Nucleic acids are divided into two main types RNA (ribonucleic acid) and DNA (deoxyribonucleic acid).
more...
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DNAunion: still more from my personal notes...
RNA
In cells, there are three principal types of RNA, each of which serves a particular function.
(1) Messenger RNA (mRNA). Messenger RNA is a complementary copy of a particular sequence of nucleotides in DNA (mRNA is transcribed from DNA) that provides the information necessary to create a particular protein. Messenger RNA remains single stranded and does not assume a three-dimensional shape.
(2) Transfer RNA (tRNA). Transfer RNA is sometimes called an adaptor molecule because of its function it forms a bridge between two informational systems (nucleic acids and proteins) by binding and transporting to the ribosomes for incorporation into a growing polypeptide the particular amino acids specified by mRNA. Because of the particular arrangement of bases in a tRNA molecule, it takes on secondary structures: the strand folds back onto itself, complementary bases find each other and pair, loops and stems form, and the resulting 2-dimensional structure resembles a cloverleaf. Transfer RNA molecules then go on to assume tertiary (three-dimensional) structures resembling the letter L.
(3) Ribosomal RNA (rRNA). Ribosomal RNA (along with certain proteins) make up the two subunits of the ribosomes, the workbenches used during protein synthesis. It has been found that it is the rRNA portion of a ribosome - and not the protein portion - that acts as the enzyme peptidyl transferase, which is responsible for catalyzing the formation of a peptide bond between the two amino acids docked in a ribosome.
DNA
DNA molecules are almost always double-stranded, and the two strands twist around a common virtual axis to assume a three-dimensional structure called a double helix (which is analogous to a spiral staircase). The two strands are complementary copies of each other that is, where the first strand has an A, the other strand has a T (and vice versa), and where the first strand has a G, the second strand has a C (and vice versa). These specified pairings (where A forms two hydrogen bonds with T, and C forms three hydrogen bonds with G) are called Watson-Crick base pairings, and always involve the pairing of a purine with a pyrimidine. The complementary nature of double-stranded DNA means that the sequence of nucleotides on one strand can be used to determine the sequence of nucleotides on the other. And as it turns out, this attribute is essential for DNA replication.
A gene can be defined as a linear series of nucleotides on a single DNA strand that contains the information required to synthesize a specific polypeptide or to produce a specific RNA molecule. Genes are arranged in a linear series on DNA molecules, and each gene location is termed a locus (plural = loci). Alleles are alternate forms of a gene that arise from mutation. Consider the gene for eye color. In a given population of humans, this gene has many forms there are alleles that code for blue eyes, alleles that code for brown eyes, alleles that code for hazel eyes, and so on (note that there are actually multiple genes that effect eye color in humans eye color is actually a polygenic trait).
In eukaryotic cells (which posses a true nucleus and other membrane-bound organelles: basically, non-bacterial cells, including plant, animal, and fungal cells), DNA is housed in the nucleus on several discrete linear molecules called chromosomes (humans, for example, have a total of 46 chromosomes, which is comprised of two separate sets one set of 23 from the mother and a corresponding set of 23 from the father). During normal cell division, all the chromosomes are first replicated, then one of the identical copies is distributed to each daughter cell. Otherwise, the new cells would not contain the information needed to carry out their functions, among which is their own survival.
more...
RNA
In cells, there are three principal types of RNA, each of which serves a particular function.
(1) Messenger RNA (mRNA). Messenger RNA is a complementary copy of a particular sequence of nucleotides in DNA (mRNA is transcribed from DNA) that provides the information necessary to create a particular protein. Messenger RNA remains single stranded and does not assume a three-dimensional shape.
(2) Transfer RNA (tRNA). Transfer RNA is sometimes called an adaptor molecule because of its function it forms a bridge between two informational systems (nucleic acids and proteins) by binding and transporting to the ribosomes for incorporation into a growing polypeptide the particular amino acids specified by mRNA. Because of the particular arrangement of bases in a tRNA molecule, it takes on secondary structures: the strand folds back onto itself, complementary bases find each other and pair, loops and stems form, and the resulting 2-dimensional structure resembles a cloverleaf. Transfer RNA molecules then go on to assume tertiary (three-dimensional) structures resembling the letter L.
(3) Ribosomal RNA (rRNA). Ribosomal RNA (along with certain proteins) make up the two subunits of the ribosomes, the workbenches used during protein synthesis. It has been found that it is the rRNA portion of a ribosome - and not the protein portion - that acts as the enzyme peptidyl transferase, which is responsible for catalyzing the formation of a peptide bond between the two amino acids docked in a ribosome.
DNA
DNA molecules are almost always double-stranded, and the two strands twist around a common virtual axis to assume a three-dimensional structure called a double helix (which is analogous to a spiral staircase). The two strands are complementary copies of each other that is, where the first strand has an A, the other strand has a T (and vice versa), and where the first strand has a G, the second strand has a C (and vice versa). These specified pairings (where A forms two hydrogen bonds with T, and C forms three hydrogen bonds with G) are called Watson-Crick base pairings, and always involve the pairing of a purine with a pyrimidine. The complementary nature of double-stranded DNA means that the sequence of nucleotides on one strand can be used to determine the sequence of nucleotides on the other. And as it turns out, this attribute is essential for DNA replication.
A gene can be defined as a linear series of nucleotides on a single DNA strand that contains the information required to synthesize a specific polypeptide or to produce a specific RNA molecule. Genes are arranged in a linear series on DNA molecules, and each gene location is termed a locus (plural = loci). Alleles are alternate forms of a gene that arise from mutation. Consider the gene for eye color. In a given population of humans, this gene has many forms there are alleles that code for blue eyes, alleles that code for brown eyes, alleles that code for hazel eyes, and so on (note that there are actually multiple genes that effect eye color in humans eye color is actually a polygenic trait).
In eukaryotic cells (which posses a true nucleus and other membrane-bound organelles: basically, non-bacterial cells, including plant, animal, and fungal cells), DNA is housed in the nucleus on several discrete linear molecules called chromosomes (humans, for example, have a total of 46 chromosomes, which is comprised of two separate sets one set of 23 from the mother and a corresponding set of 23 from the father). During normal cell division, all the chromosomes are first replicated, then one of the identical copies is distributed to each daughter cell. Otherwise, the new cells would not contain the information needed to carry out their functions, among which is their own survival.
more...
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Central Dogma of Molecular Biology
Information flow in cells is always from nucleic acids to proteins: never does it flow in the opposite direction. As a rule of thumb, the flow of biological information starts with DNA, which is then copied into RNA (transcription), which is then used in the production of proteins (translation). In no instance has it ever been found that information from proteins traveled this pathway in reverse order, incorporating its information into the DNA of the organism (however, an enzyme called reverse transcriptase, found for example in retroviruses, can create DNA from an RNA template). This unidirectional flow of information, each step of which will be discussed briefly, is generally represented symbolically as follows:
[figure omitted]
DNA Replication
During DNA replication, an identical copy of an existing DNA molecule is made. This is a very complex process and only the highlights will be covered. Also, please note that despite what many sources incorrectly state, DNA is NOT self-replicating (as will become clear from the following details).
In the general cell cycle, in which cells continually grow and divide, a stage called the S phase is reached in which the DNA needs to be replicated. Two identical copies of the parent cells genetic material are needed so that one copy can be passed on to each of the two soon-to-be daughter cells. These two genetically identical daughter cells will be produced from the mitotic processes of karyokinesis (division of the nucleus) and cytokinesis (division of the cytoplasm).
First, localized regions of the double-stranded, helical DNA must be unwound and split into two separate single strands. Instrumental in the unwinding of the helix are enzymes known as DNA helicases. Once the single strands exist, they will naturally rejoin since the sequence of nucleotides on one strand is complementary to the sequence of nucleotides on the other strand (and thus, will tend to undergo Watson-Crick base pairing spontaneously). So another set of proteins, called SSBP (Single-Stranded Binding Proteins), stabilize the individual single strands of DNA in their open position. One of the several DNA polymerases is then able to begin synthesizing a new strand of DNA from each original strand using the Watson-Crick base pairing rules. Actually, the previous statement is not entirely accurate. DNA polymerases cannot start a new strand of DNA they can only elongate an existing strand. How then does the process proceed? By using another protein enzyme called primase a DNA-dependent RNA polymerase. This enzyme creates an RNA primer (a short segment consisting of several RNA nucleotides complementary to the DNA template) which the DNA polymerases then elongate (the RNA nucleotides will be replaced with DNA nucleotides later). As mentioned before, the incorporation of nucleotides into a polynucleotide is an energy-consuming process and the energy is provided by the hydrolysis of the two terminal phosphate groups from the incoming nucleoside triphosphates. As replication proceeds, the portions of DNA ahead of the advancing replication fork become greatly supercoiled (as an analogy, if you take a rubber band and twist it several times, then place a pencil in between the two strands and move it towards one end, the rubber band ahead of the advancing pencil will become more tightly coiled). This extra-tight coiling will cause polymerization to halt and must be eliminated. A topoisomerase (an enzyme that reduces or increases supercoiling of DNA) called DNA gyrase snips the double-stranded DNA ahead of the replication fork in order to allow the supercoiling to relax, then reseals the cut, and replication proceeds. Once a segment of DNA has been synthesized, one of the DNA polymerases replaces all of the RNA primers with DNA. Finally, any individual segments of synthesized DNA are bonded together by an enzyme called DNA ligase to form a single, continuous strand.
The result of the above processes is the creation of an identical copy of the cells genetic material. Since each new DNA molecule consists of one original strand and one newly-synthesized strand, the process is called semi-conservative replication (the original double-stranded DNA is semi-conserved since one, but not both, of its strands remains in each of the two final products).
This discussion has been a mere overview. For example, topics such as lagging strand synthesis and its peculiarities, and the handling of histones in eukaryotes, were not mentioned.
more...
Information flow in cells is always from nucleic acids to proteins: never does it flow in the opposite direction. As a rule of thumb, the flow of biological information starts with DNA, which is then copied into RNA (transcription), which is then used in the production of proteins (translation). In no instance has it ever been found that information from proteins traveled this pathway in reverse order, incorporating its information into the DNA of the organism (however, an enzyme called reverse transcriptase, found for example in retroviruses, can create DNA from an RNA template). This unidirectional flow of information, each step of which will be discussed briefly, is generally represented symbolically as follows:
[figure omitted]
DNA Replication
During DNA replication, an identical copy of an existing DNA molecule is made. This is a very complex process and only the highlights will be covered. Also, please note that despite what many sources incorrectly state, DNA is NOT self-replicating (as will become clear from the following details).
In the general cell cycle, in which cells continually grow and divide, a stage called the S phase is reached in which the DNA needs to be replicated. Two identical copies of the parent cells genetic material are needed so that one copy can be passed on to each of the two soon-to-be daughter cells. These two genetically identical daughter cells will be produced from the mitotic processes of karyokinesis (division of the nucleus) and cytokinesis (division of the cytoplasm).
First, localized regions of the double-stranded, helical DNA must be unwound and split into two separate single strands. Instrumental in the unwinding of the helix are enzymes known as DNA helicases. Once the single strands exist, they will naturally rejoin since the sequence of nucleotides on one strand is complementary to the sequence of nucleotides on the other strand (and thus, will tend to undergo Watson-Crick base pairing spontaneously). So another set of proteins, called SSBP (Single-Stranded Binding Proteins), stabilize the individual single strands of DNA in their open position. One of the several DNA polymerases is then able to begin synthesizing a new strand of DNA from each original strand using the Watson-Crick base pairing rules. Actually, the previous statement is not entirely accurate. DNA polymerases cannot start a new strand of DNA they can only elongate an existing strand. How then does the process proceed? By using another protein enzyme called primase a DNA-dependent RNA polymerase. This enzyme creates an RNA primer (a short segment consisting of several RNA nucleotides complementary to the DNA template) which the DNA polymerases then elongate (the RNA nucleotides will be replaced with DNA nucleotides later). As mentioned before, the incorporation of nucleotides into a polynucleotide is an energy-consuming process and the energy is provided by the hydrolysis of the two terminal phosphate groups from the incoming nucleoside triphosphates. As replication proceeds, the portions of DNA ahead of the advancing replication fork become greatly supercoiled (as an analogy, if you take a rubber band and twist it several times, then place a pencil in between the two strands and move it towards one end, the rubber band ahead of the advancing pencil will become more tightly coiled). This extra-tight coiling will cause polymerization to halt and must be eliminated. A topoisomerase (an enzyme that reduces or increases supercoiling of DNA) called DNA gyrase snips the double-stranded DNA ahead of the replication fork in order to allow the supercoiling to relax, then reseals the cut, and replication proceeds. Once a segment of DNA has been synthesized, one of the DNA polymerases replaces all of the RNA primers with DNA. Finally, any individual segments of synthesized DNA are bonded together by an enzyme called DNA ligase to form a single, continuous strand.
The result of the above processes is the creation of an identical copy of the cells genetic material. Since each new DNA molecule consists of one original strand and one newly-synthesized strand, the process is called semi-conservative replication (the original double-stranded DNA is semi-conserved since one, but not both, of its strands remains in each of the two final products).
This discussion has been a mere overview. For example, topics such as lagging strand synthesis and its peculiarities, and the handling of histones in eukaryotes, were not mentioned.
more...
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seebs
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Similarities in design are not particularly good proof of a common creator; different people might design things in certain common ways, and the same person might design things different ways in different contexts.
The question is, why would God make our legs relatively awkward and breakable, just to "reuse" some of the design He used in other mammals? That'd be silly.
The question is, why would God make our legs relatively awkward and breakable, just to "reuse" some of the design He used in other mammals? That'd be silly.
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DNAunion: more from my personal notes
Transcription
Transcription is the process by which segments of DNA are copied into complementary strands of mRNA, rRNA, or tRNA. Since the informations language is not being changed it begins as nucleotides and ends as nucleotides the term transcription is appropriate (transcribing relates to the copying of information).
A series of three consecutive DNA nucleotides is called a triplet, but once they have been transcribed into mRNA, that series of three consecutive mRNA nucleotides is then called a codon (because it will code for a particular amino acid during translation).
Transcription can be divided into four stages: binding, initiation, elongation, and termination (these will not be described individually). As in DNA replication, the DNA double helix must be unwound and the strands separated in order for enzymes to gain access to the individual nucleotides. An RNA polymerase binds to a particular DNA nucleotide sequence, called a promoter region, that is usually located just upstream (i.e., before) the gene to be transcribed. Similar to DNA replication, a new complementary nucleotide strand is created using the existing DNA strand as a template. However, unlike DNA replication, uracil (instead of thymine) is incorporated into the newly-synthesized strand for all occurrences of adenine on the template. Also unlike DNA replication, which continues until the entirety of the cells genetic information has been processed, transcription ceases as soon as a termination sequence is encountered (conceptually, once a single gene has been transcribed, the polymerase enzyme its job complete - falls off the template).
Note that there were many, many topics related to transcription that were not addressed: such as gene regulation (which genes get expressed/transcribed and which are not), the various transcription factors (enzymes required for binding and initiation), introns (intervening, non-expressed nucleotide sequences), exons (expressed nucleotide sequences that must be ligated together once all of the introns have been excised), ribozymes (catalytic RNA molecules, such as those that can catalyze the excision of introns internal to their own sequence), RNA processing (addition of poly(A) tails and 5 caps), and so on. The reader, if interested, is again referred to an introductory text on cell biology.
more...
Transcription
Transcription is the process by which segments of DNA are copied into complementary strands of mRNA, rRNA, or tRNA. Since the informations language is not being changed it begins as nucleotides and ends as nucleotides the term transcription is appropriate (transcribing relates to the copying of information).
A series of three consecutive DNA nucleotides is called a triplet, but once they have been transcribed into mRNA, that series of three consecutive mRNA nucleotides is then called a codon (because it will code for a particular amino acid during translation).
Transcription can be divided into four stages: binding, initiation, elongation, and termination (these will not be described individually). As in DNA replication, the DNA double helix must be unwound and the strands separated in order for enzymes to gain access to the individual nucleotides. An RNA polymerase binds to a particular DNA nucleotide sequence, called a promoter region, that is usually located just upstream (i.e., before) the gene to be transcribed. Similar to DNA replication, a new complementary nucleotide strand is created using the existing DNA strand as a template. However, unlike DNA replication, uracil (instead of thymine) is incorporated into the newly-synthesized strand for all occurrences of adenine on the template. Also unlike DNA replication, which continues until the entirety of the cells genetic information has been processed, transcription ceases as soon as a termination sequence is encountered (conceptually, once a single gene has been transcribed, the polymerase enzyme its job complete - falls off the template).
Note that there were many, many topics related to transcription that were not addressed: such as gene regulation (which genes get expressed/transcribed and which are not), the various transcription factors (enzymes required for binding and initiation), introns (intervening, non-expressed nucleotide sequences), exons (expressed nucleotide sequences that must be ligated together once all of the introns have been excised), ribozymes (catalytic RNA molecules, such as those that can catalyze the excision of introns internal to their own sequence), RNA processing (addition of poly(A) tails and 5 caps), and so on. The reader, if interested, is again referred to an introductory text on cell biology.
more...
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