Nucleic Acid Written Report

8/9/2019 Nucleic Acid Written Report

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Nucleic Acids

Nucleic Acids - extremely complex molecules produced by living cells andviruses. Their name comes from their initial isolation from the nuclei of living cells.

Certain nucleic acids, however, are found not in the cell nucleus but in cellcytoplasm.

Brief History

The first isolation of what we now refer to as DNA was accomplished byJohann Friedrich Miescher circa 1870. He reported finding a weakly acidicsubstance of unknown function in the nuclei of human white blood cells, and namedthis material "nuclein". A few years later, Miescher separated nuclein into proteinand nucleic acid components. In the 1920's nucleic acids were found to be major

components of chromosomes, small gene-carrying bodies in the nuclei of complexcells. Elemental analysis of nucleic acids showed the presence of phosphorus, inaddition to the usual C, H, N & O. Unlike proteins, nucleic acids contained no sulfur.Complete hydrolysis of chromosomal nucleic acids gave inorganic phosphate, 2-deoxyribose (a previously unknown sugar) and four different heterocyclic bases(shown in the following diagram). To reflect the unusual sugar component,chromosomal nucleic acids are called deoxyribonucleic acids, abbreviated DNA.

Analogous nucleic acids in which the sugar component is ribose are termedribonucleic acids, abbreviated RNA. The acidic character of the nucleic acids wasattributed to the phosphoric acid moiety.

F unctions

Nucleic acids have at least two functions :

y to pass on hereditary characteristics from one generation to the next,y and to trigger the manufacture of specific proteins.

Nucleic acids are responsible for storing and transferring genetic information.They are enormous molecules made up of long strands of subunits, called bases

that are arranged in a precise sequence. These are read by other components of the cell and used as a guide in making proteins.

C oncepts to Remember

1. Nucleotides - the monomers for nucleic acid polymers, are composed of apentose sugar bonded to both a phosphate group and a nitrogen-containingheterocyclic bases. The pentose sugar must be either ribose or deoxyribose.


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A molecule of DNA consists of two chains, strands composed of a largenumber of chemical compounds, called nucleotides, linked together to form a chain.

These chains are arranged like a ladder that has been twisted into the shape of awinding staircase, called a double helix. Each nucleotide consists of three units: asugar molecule called deoxyribose, a phosphate group, and one of four differentnitrogen-containing compounds called bases. The four bases are adenine (A),guanine (G), thymine (T), and cytosine (C). The deoxyribose molecule occupies thecenter position in the nucleotide, flanked by a phosphate group on one side and abase on the other. The phosphate group of each nucleotide is also linked to thedeoxyribose of the adjacent nucleotide in the chain. These linked deoxyribose-phosphate subunits form the parallel side rails of the ladder. The bases face inward

toward each other, forming the rungs of the ladder.


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The chemical structure of DNA

DNA is a long polymer made from repeating units called nucleotides. The

DNA chain is 22 to 26 ngstrms wide (2.2 to 2.6 nanometres), and one nucleotideunit is 3.3 ngstroms (0.33 nanometres) long. Although each individual repeatingunit 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.

The nucleotides in one DNA strand have a specific association with thecorresponding nucleotides in the other DNA strand. Because of the chemical affinityof the bases, nucleotides containing adenine are always paired with nucleotides

containing thymine, and nucleotides containing cytosine are always paired withnucleotides containing guanine. The complementary bases are joined to each other by weak chemical bonds called hydrogen bonds


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RNA

Ribonucleic acid or RNA is a nucleic acid, consisting of many nucleotidesthat form a polymer. Each nucleotide consists of a nitrogenous base, a ribose sugar,and a phosphate. RNA plays several important roles in the processes of translatinggenetic information from deoxyribonucleic acid (DNA) into proteins. One type of RNAacts as a messenger between DNA and the protein synthesis complexes known asribosomes, others form vital portions of the structure of ribosomes, act as essentialcarrier molecules for amino acids to be used in protein synthesis, or change whichgenes are active.

RNA is very similar to DNA, but differs in a few important structural details:RNA is usually single stranded, while DNA is usually double stranded. RNAnucleotides contain ribose while DNA contains deoxyribose (a type of ribose thatlacks one oxygen atom), and RNA uses the nucleotide uracil in its composition,instead of thymine which is present in DNA. RNA is transcribed from DNA byenzymes called RNA polymerases and is generally further processed by other enzymes, some of them guided by non-coding RNAs.

C lassification of Bases

There are four different heterocyclic amine bases in deoxyribonucleotides.Two are substituted purines (adenine and guanine), and two are substitutedpyrimides (cytosine and thymine). Adenine, guanine, and cytosine also occur inRNA, but thymine is replaced in RNA by a different pyrimidine base called uracil.

A U G sugar phosphate sugar phosphate sugar phosphate sugar ...RNA


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Base-catalyzed hydrolysis of DNA gave four nucleoside products, whichproved to be N-glycosides of 2'-deoxyribose combined with the heterocyclic amines.The base components are colored green, and the sugar is black. As noted in the 2'-deoxycytidine structure on the left, the numbering of the sugar carbons makes use of primed numbers to distinguish them from the heterocyclic base sites. The

corresponding N-glycosides of the common sugar ribose are the building blocks of RNA, and are named adenosine, cytosine, guanosine and uridine (a thymidineanalog missing the methyl group).


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C omponents of Nucleic Acid

The nucleic acids are very large molecules that have two main parts. Thebackbone of a nucleic acid is made of alternating sugar and phosphate moleculesbonded together in a long chain, represented below:

sugar phosphate sugar phosphateEach of the sugar groups in the backbone is attached (via the bond shown in

red) to a third type of molecule called a nucleotide base:

Though only four different

nucleotide bases can occur in a nucleic acid, each nucleic acid contains millions of bases bonded to it. The order in which these nucleotide bases appear in the nucleicacid is the coding for the information carried in the molecule. In other words, thenucleotide bases serve as a sort of genetic alphabet on which the structure of eachprotein in our bodies is encoded.

Base pairing

nucleotidebase

nucleotidebase

| |

sugar Phosphate sugar phosphate


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At top, a G C base pair with three hydrogen bonds. At the bottom, AT basepair with two hydrogen bonds. Hydrogen bonds are shown as dashed lines.

Each type of base on one strandforms a bond with just one type of base

on the other strand. This is calledcomplementary base pairing. Here,purines form hydrogen bonds topyrimidines, with A bonding only to T, andC bonding only to G. This arrangement of two nucleotides binding together acrossthe double helix is called a base pair. In adouble helix, the two strands are also heldtogether via forces generated by thehydrophobic effect and pi stacking, whichare not influenced by the sequence of the

DNA. As hydrogen bonds are notcovalent, they can be broken and rejoinedrelatively easily. The two strands of DNAin a double helix can therefore be pulledapart like a zipper, either by a mechanicalforce or high temperature. As a result of this complementarily, all the information inthe double-stranded sequence of a DNA

helix is duplicated on each strand, which is vital in DNA replication. Indeed, thisreversible and specific interaction between complementary base pairs is critical for all the functions of DNA in living organisms.

The two types of base pairs form different numbers of hydrogen bonds, ATforming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, ontop). The GC base pair is therefore stronger than the AT base pair. As a result, it isboth the percentage of GC base pairs and the overall length of a DNA double helixthat determine the strength of the association between the two strands of DNA. LongDNA helices with a high GC content have stronger-interacting strands, while shorthelices with high AT content have weaker-interacting strands. Parts of the DNAdouble helix that need to separate easily, such as the TATAAT Pribnow box inbacterial promoters, tend to have sequences with a high AT content, making thestrands easier to pull apart. In the laboratory, the strength of this interaction can bemeasured by finding the temperature required to break the hydrogen bonds, their melting temperature (also called T m value). When all the base pairs in a DNA doublehelix melt, the strands separate and exist in solution as two entirely independentmolecules. These single-stranded DNA molecules have no single common shape,but some conformations are more stable than others.


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Recombinant DNA

The DNA molecules of all life forms, from oak trees to sea horses, have the samestructure and the same four bases. Scientists have made use of these similaritiesin a technology called recombinant DNA. In this laboratory method, one or more

genes of an organism are introduced into a second organism. The new genes,sometimes known as foreign DNA, become functional in the second organism andproduce a desired protein. In this way, scientists can create changes in thegenetic makeup of an organism that would be unlikely to occur through naturalprocesses.

Restriction EnzymesProduced by some kinds of bacteria, restriction enzymes recognize specificsequences of DNA and cut the double strand where the sequence occurs. Treatingthe DNA of two different organisms with the same restriction enzyme producescomplementary fragments, or fragments with ends that fit together. These can becombined in a hybrid DNA molecule that, if part of a living cell, expresses traits of both parents.

DNA MUTATION S

Mutations in DNA sequences generally occur through one of two processes:


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1. DNA damage from environmental agents such as ultraviolet light (sunshine),nuclear radiation or certain chemicals

2. Mistakes that occur when a cell copies its DNA in preparation for cell division.

DN A damage from environmental agents

Modifying nucleotide bases

Ultraviolet light, nuclear radiation and certain chemicals can damage DNA byaltering nucleotide bases so that they look like other nucleotide bases.

When the DNA strands are separated and copied, the altered base will pair with anincorrect base and cause a mutation. In the example below a "modified" G now pairswith T, instead of forming a normal pair with C.


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Breaking the phosphate backbone

Environmental agents such as nuclear radiation can damage DNA bybreaking the bonds between oxygens (O) and phosphate groups (P).

Breaking the phosphate backbone of DNA within a gene creates a

mutated form of the gene. It is possible that the mutated gene will

produce a protein that functions differently.


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C ells with broken DNA will attempt to fix the broken ends by joining these

free ends to other pieces of DNA within the cell. This creates a type of

mutation called "translocation." If a translocation breakpoint occurs within

or near a gene, that gene's function may be affected.

2. Mistakes created during DNA duplication

Prior to cell division, each cell must duplicate its entire DNA sequence.

This process is called DNA replication.

DNA replication begins when a protein called DNA helicase separates the

DNA molecule into two strands.

Next, a protein called DNA polymerase copies each strand of DNA to

create two double-stranded DNA molecules.


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M utations result when the DNA polymerase makes a mistake, which

happens about once every 100,000,000 bases.

Actually, the number of mistakes that remain incorporated into the DNA

is even lower than this because cells contain special DNA repair proteins

that fix many of the mistakes in the DNA that are caused by mutagens.

The repair proteins see which nucleotides are paired incorrectly, and then

change the wrong base to the right one.

Nucleic Acid and Heredity

Replication

In most cellular organisms, replication of a DNA molecule takes place in thecell nucleus and occurs just before the cell divides. Replication begins with theseparation of the two polynucleotide chains, each of which then acts as a templatefor the assembly of a new complementary chain. As the old chains separate, eachnucleotide in the two chains attracts a complementary nucleotide that has beenformed earlier by the cell. The nucleotides are joined to one another by hydrogenbonds to form the rungs of a new DNA molecule. As the complementary nucleotidesare fitted into place, an enzyme called DNA polymerase links them together bybonding the phosphate group of one nucleotide to the sugar molecule of theadjacent nucleotide, forming the side rail of the new DNA molecule. This processcontinues until a new polynucleotide chain has been formed alongside the old one,forming a new double-helix molecule.

(Transcription and Translation)


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y Ribosomal RNA (rRNA) is found in the cell's ribosomes, the specializedstructures that are the sites of protein synthesis).

y Transfer RNA (tRNA) carries amino acids to the ribosomes for incorporationinto a protein.

y Messenger RNA (mRNA) carries the genetic blueprint copied from thesequence of bases in a cell's DNA. This blueprint specifies the sequence of amino acids in a protein. All three types of RNA are formed as needed,using specific sections of the cell's DNA as templates.

Protein synthesis begins with the separation of a DNA molecule into twostrands. In a process called transcription , a section of one strand acts as atemplate, or pattern, to produce a new strand called messenger RNA (mRNA). The

mRNA leaves the cell nucleus and attaches to the ribosomes, specialized cellular structures that are the sites of protein synthesis. Amino acids are carried to theribosomes by another type of RNA, called transfer RNA (tRNA). In a process calledtranslation , the amino acids are linked together in a particular sequence, dictatedby the mRNA, to form a protein.

Transcription

Protein synthesis in a cell begins with initiation, when a chain of messenger RNA (mRNA) carrying genetic instructions from deoxyribonucleic acid (DNA)

attaches to a ribosome. The mRNA instructs the ribosome how to assemble aminoacids to form a protein. Two molecules of transfer RNA (tRNA), each carrying anamino acid, join the ribosome-messenger RNA complex at two positions called P-site and A-site. A chemical bond known as a peptide bond is formed between thefirst two amino acids.


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During elongation the tRNA in the P-site detaches from its amino acid andfloats away from the complex while the tRNA carrying the two bonded amino acidsmoves from the A-site over to the P-site. This leaves the A-site open for a new tRNAmolecule carrying a third amino acid to attach to the ribosome. The new amino acidbonds to the second amino acid with another peptide bond. Again, one tRNA isreleased and the remaining tRNA molecule, now carrying a chain of three aminoacids, moves over to the P-site. The ribosome coordinates this cycle repeatedly untiltermination occurs, when the ribosome encounters a stop signal on the mRNA. Thecompleted protein, which may be a chain of hundreds of amino acids, is releasedfrom the ribosome.

In general, DNA carries the genetic instructions for making all cellular structures. Since all cells contain ribosomes, scientists are comparing DNAinstructions for making ribosomes in different species to learn how closely thespecies are related.


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P ROTEIN SY NTHE S IS

Protein Synthesis One of a cells most important tasks is the synthesis of proteins,giant molecules that underlie most cellular functions. The hereditary materialknown as deoxyribonucleic acid (DNA), found within the nucleus of a cell,orchestrates a series of steps resulting in the manufacture of proteins tailored tomeet the needs for a cells development and growth.

1. P rotein S tructure and C ell F unction

Proteins play essential roles in thecells of all living creatures they serve asbuilding blocks of cells, control chemical

reactions, and transport materials to and fromcells. Proteins are composed of long chainsof amino acids. The specific sequence of amino acids in a chain determines the exact

function of the protein.

2. G enes C ode for P rotein S tructure

Genes, located in the cell nucleus, areindividual sections of the long, coiled

molecules called deoxyribonucleic acid(DNA). A DNA molecule consists of twostrands of chemical units nucleotides. Thetwo strands in DNA attach to each other bypairings of four types of nucleotide structures

called bases: thymine (T), adenosine (A), cytosine (C), and guanine (G).These bases pair in a very specific way: T binds only with A, and C bindsonly with G. A gene made up of a specific sequence of nucleotides, andthis sequence determines the type of protein produced. But genes do notmake proteins directly. Instead they direct the formation an intermediarymolecule known as messenger ribonucleic acid (mRNA) from which the

protein making instructions will be carried out.

3. DNA S trands S eparate

In preparation for the manufacture of mRNA, a DNA molecule in the nucleusseparates into two strands in the region of a


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gene carrying instructions for a specific protein. Each sequence of three bases in a DNA strand is called a triplet, which is a code for oneof 20 amino acids, the building blocks of protein.

4. Transcription

One DNA strand acts as the template,or pattern, for the construction of mRNA. Inthis process, called transcription, free floatingRNA nucleotides traveling in the cell nucleuspair with complementary bases on the DNAtemplate strand. RNA nucleotides use thebase uracil (U) instead of thymine (T). As

RNA nucleotides pair with DNA bases, uracil (U) from the RNA pairswith adenosine (A) on the DNA strand, adenosine from the RNA pairs

with thymine (T) on the DNA strand, and cytosine (C) pairs withguanine (G). After pairing with bases, adjacent RNA nucleotides join toform a precursor mRNA strand. While each three-base sequence onthe DNA template is called triplet, the corresponding three-basesequence on the mRNA strand is called a codon.

5. Removal of Introns

The precursor mRNA strand containscoding regions called exons that code for aprotein. The exons are separated bynoncoding regions called introns. Before themRNA strands is used in protein synthesis,the intron coding regions drop out.

6. Messenger RNA Binds to Ribosome

Once mRNA is completely formed, themRNA strand leaves the cell nucleus to enter the cytoplasm, where it attaches to a cellular organelle called a ribosome. Proteinsynthesis occurs in the ribosomes.


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7 . Transfer RNA Binds to Amino Acid

Scattered throughout the cytoplasmare different types of transfer RNA (tRNA),

each capable of attaching to one of the 20different amino acids that are used to build aprotein. One end of a tRNA moleculeattaches to a specific amino acid asdetermined by the anticodon at the other end

of the tRNA. An anticodon is a three-base sequence that recognizes aparticular mRNA codon with a complementary base sequence.

8. Translation After a tRNA binds to an amino acid, it

carries the amino acid to the mRNA-ribosomecomplex. The anticodon of the tRNA binds toa codon on the mRNA. The sequence of bases in the codon code for the type of aminoacid carried by the tRNA. A second tRNAattaches to the mRNA ribosome complex.

The first tRNA transfers its amino acid to the amino acid of the second tRNA beforedetaching from the ribosome. The second tRNA now carries two amino acids, whichform the beginning of a polypeptide chain. The ribosome then moves the mRNAstrand so that the next mRNA codon is positioned to attract and bind to a new tRNA.

9. P olypeptide F ormation Halted

The ribosome continues to move themRNA strand as the polypeptide chain isbuilt. The polypeptide chain is completedwhen the ribosome comes to an mRNAcodon known as the stop codon, whichinstructs the ribosome that the manufactureof the protein is finished.


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10. P rotein F ormation C omplete

Released from the ribosome, the newly

formed protein is an exact replica of thestructure encoded in the original DNA strand.

The G enetic C ode

S econd P osition of C odon

T C A G

F ir st

P osition

T

TTT Phe [F]TTC Phe [F]TTA Leu [L]TTG Leu [L]

TCT Ser [S]TCC Ser [S]TCA Ser [S]TCG Ser [S]

TAT Tyr [Y]TAC Tyr [Y]TAA Te r [end]TAG Te r [end]

TGT Cys [C]TGC Cys [C]TGA Te r [end]TGG Trp [W]

T C A G T

hir d

P osition

C

CTT Leu [L]CTC Leu [L]CTA Leu [L]

CTG Leu [L]

CCT Pro [P]CCC Pro [P]CCA Pro [P]

CCG Pro [P]

CAT His [H]CAC His [H]CAA Gln [Q]

CAG Gln [Q]

CGT Arg [R]CGC Arg [R]CGA Arg [R]

CGG Arg [R]

T C A G

A

ATT Ile [I] ATC Ile [I] ATA Ile [I] ATG Met [M]

ACT Thr [T] ACC Thr [T] ACA Thr [T] ACG Thr [T]

AAT Asn [N] AAC Asn [N] AAA Lys [K] AAG Lys [K]

AGT Ser [S] AGC Ser [S] AGA Arg [R] AGG Arg [R]

T C A G

G

GTT Val [V]GTC Val [V]GTA Val [V]

GTG Val [V]

GCT Ala [A]GCC Ala [A]GCA Ala [A]

GCG Ala [A]

GAT Asp [D]GAC Asp [D]GAA Glu [E]

GAG Glu [E]

GGT Gly [G]GGC Gly [G]GGA Gly [G]

GGG Gly [G]

T C A G

An explanation of the G enetic C ode: DNA is a two-stranded molecule. Eachstrand is a polynucleotide composed of A (adenosine), T (thymidine), C (cytidine),


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and G (guanosine) residues polymerized by "dehydration" synthesis in linear chainswith specific sequences. Each strand has polarity, such that the 5'-hydroxyl (or 5'-phospho) group of the first nucleotide begins the strand and the 3'-hydroxyl group of the final nucleotide ends the strand; accordingly, we say that this strand runs 5' to 3'("F iv e p ri me to th r ee p ri me ") . It is also essential to know that the two strands of DNA

runan

t i p

arall e

l such that one strand runs 5' -> 3' while the other one runs 3' -> 5'. Ateach nucleotide residue along the double-stranded DNA molecule, the nucleotides

are complementary. That is, A forms two hydrogen-bonds with T; C forms threehydrogen bonds with G . In most cases the two-stranded, antiparallel,complementary DNA molecule folds to form a helical structure which resembles aspiral staircase. This is the reason why DNA has been referred to as the "DoubleHelix".

One strand of DNA holds the information that codes for various genes; this strand isoften called the template strand or antisense strand (containing anticodons). Theother, and complementary, strand is called the coding strand or sense strand

(containing codons). Since mRNA is made from the template strand, it has the sameinformation as the coding strand. The table above refers to triplet nucleotide codonsalong the sequence of the coding or sense strand of DNA as it runs 5' -> 3'; the codefor the mRNA would be identical but for the fact that RNA contains U (uridine) rather than T.

An example of two complementary strands of DNA would be:

(5' -> 3') AT GG AATT C TC G C TC (Coding, sense strand)(3' 3') AUGG

AAUUC

UC G C

UC

(mRNA made from Template strand)Since amino acid residues of proteins are specified as triplet codons, the proteinsequence made from the above example would be Met-Glu-Phe-Ser-Leu...(MEFSL...).

Practically, codons are "decoded" by transfer RNAs (tRNA) which interact with aribosome-bound messenger RNA (mRNA) containing the coding sequence. Thereare 64 different tRNAs, each of which has an anticodon loop (used to recognizecodons in the mRNA). 61 of these have a bound amino acyl residue; the appropriate"charged" tRNA binds to the respective next codon in the mRNA and the ribosomecatalyzes the transfer of the amino acid from the tRNA to the growing (nascent)protein/polypeptide chain. The remaining 3 codons are used for "punctuation"; thatis, they signal the termination (the end) of the growing polypeptide chain.

Lastly, the Genetic Code in the table above has also been called "The UniversalGenetic Code". It is known as "universal", because it is used by all known organismsas a code for DNA, mRNA, and tRNA. The universality of the genetic codeencompases animals (including humans), plants, fungi, archaea, bacteria, and


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viruses. However, all rules have their exceptions, and such is the case with theGenetic Code; small variations in the code exist in mitochondria and certainmicrobes. Nonetheless, it should be emphasized that these variances represent onlya small fraction of known cases, and that the Genetic Code applies quite broadly,certainly to all known nuclear genes.

How to C rack the C ode

DNA - the Blueprint of Life

Every living organism contains within itself theinformation it needs to build a new organism. Thisinformation, you could think of it as a blueprint of life, isstored in the organism's genome. The genome is made upof a material called DNA, which stands for

deoxyribonucleic acid. If you take a really, really close look at the DNA molecule youwill see that it looks like an ordinary ladder, although somewhat twisted. The stepsthat connect the two strands in this ladder are composed of four different moleculesof the same type, called nucleotides. In DNA they are A, T, C and G; where A standsfor adenine, T for thymine, C for cytosine and finally G for guanine.

RNA - a Blueprint C opy

When an organism needs to use the data stored inthe genome, e.g. to build components of a new cell, a copyof the required DNA part is made. This copy is called RNAand is almost identical to DNA. Just like DNA, RNA is an

abbreviated form of a chemical name which in the case of RNA is ribonucleic acid.Unlike the double stranded DNA, RNA is only made up of a single strand.Furthermore, the base T, thymine, is replaced by U, uracil in RNA. This RNA stringis used by the organism as a template when it builds protein molecules, sometimescalled the building blocks of the body. For example, your muscles and hair aremostly made up of proteins.

Amino Acids Make Up the P rotein

Proteins can vary in length and size and look very different, but they are allcomposed of smaller units, i.e. molecules called amino acids. Inside our body thereare 20 amino acids all with different chemical and physical properties. In the tablebelow their names and abbreviations can be found.


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Name Abbrev. S hort Abbrev.

Alanine Ala A Arginine Arg R

Asparagine Asn Naspartic acid Asp DCysteine Cys CGlutamine Gln Qglutamic acid Glu EGlycine Gly GHistidine His HIsoleucine Ile I

Leucine Leu LLysine Lys KMethionine Met MPhenylalanine Phe FPraline Pro PSerine Ser SThreonine Thr TTryptophan Trp WTyrosine Tyr YValine Val V

But how does the organism know how to assemble these proteinscompromising of the different amino acids? How can the organism "read" the RNA,the blueprint copy, and how is the information written in the RNA?

The RNA Message

The alphabet in the RNA molecule contains 4 letters,i.e. A, U, C, G as previously mentioned. To construct aword in the RNA language, three of these letters aregrouped together. This three-letter word are often referred

to as a triplet or a codon. An example of such a codon is ACG. The letters don't haveto be of different kinds, so UUU is also a valid codon. These codons are placed after


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each other in the RNA molecule, to construct a message, a RNA sequence. Thismessage will later be read by the protein producing machinery in the body.

The RNA part to the left contains 39 letters and since each codon contains 3letters, 13 codons are present (39 letters divided by 3 letters equals 13 words or

codons.)

But how does these RNA words get interpreted by the organism into the finalproduct, the protein?

Interpreting the Message

Every organism has an almost identical system that is able to read the RNA,interpret the different codons and construct a protein with various combinations of the amino acids mentioned previously. In fact every RNA word or codon,corresponds to one single amino acid. These codons and their correlation with theamino acids in a protein sequence is what defines the genetic code. Below is aschematic animation of this process displayed.

Visualizing the C ode

One way to visualize the genetic code, the connection between a codon andan amino acid, is with a table. In the example below, the letter in the outermost left

column represents the first letter in the codon. The letters in the top row representsthe second codon letter and finally the letters in the outermost right columnrepresents the third codon letter.


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U C A G

U Phe Ser Tyr Cys U

Phe Ser Tyr Cys C Leu Ser STOP STOP A

Leu Ser STOP Trp G C Leu Pro His Arg U

Leu Pro His Arg C

Leu Pro Gln Arg A

Leu Pro Gln Arg G

A Ile Thr Asn Ser U Ile Thr Asn Ser C

Ile Thr Lys Arg A

Met Thr Lys Arg G G Val Ala Asp Gly U

Val Ala Asp Gly C

Val Ala Glu Gly A

Val Ala Glu Gly G

The genetic code is an important key in the understanding of the process in the bodywhen the DNA copy - RNA, is translated into the functional molecules, the proteins.


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TE C HNOLO G IC AL IN S TITUTE O F THE P HILIPP INES Department of Chemical Engineering363 P. Casal St. Quiapo, Manila

Biochemical Engineering

Presented by:

Bernardo, ArpelioCordova, Jhoanna RoseFontillas, FatimaLim, YvettePlata, Cherry Ann

Presented to:Engr. F. Magnaye(Professor)

February 20, 2008

Nucleic Acid Written Report

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