Nucleic AcidsDNA and RNA

Hundreds of thousands of proteins exist inside each one of us to help carry out our daily functions. These proteins are produced locally, assembled piece-by-piece to exact specifications

This information, detailing the specific structure of the proteins inside of our bodies, is stored in a set of molecules called nucleic acids.

Nucleic Acids DNA and RNADNA - deoxyribonucleic acidRNA - ribonucleic acid

DNA- stores genetic informationRNA - use in protein synthesis for putting genetic information

COMPOSITION OF NUCLEIC ACIDSNucleic Acids are POLYMERS

Proteins are polypeptides, Carbohydrates are polysaccharides Nucleic acid is polynucleotide- made of NUCLEOTIDES

Structure of NUCLEOTIDE

The deoxyribonucleic acid, DNA, is a long chain of nucleotides which consist ofDeoxyribose (a pentose = sugar with 5 carbons) Phosphoric Acid Organic (nitrogenous) bases (Purines - Adenine and Guanine, or Pyrimidines -Cytosine and Thymine

*The Structure of Nucleic AcidNucleic Acid is a polymer of nucleotides It is a very large molecule that have two main parts. The backbone of a nucleic acid is made of alternating sugar and phosphate molecules bonded together in a long chain phosphodiester bonds. Each of the sugar groups in the backbone is attached (via the bond shown in blue) to a third type of molecule called a nucleotide base.

The Structure of Nucleic AcidsThe phosphodiester bonds link the 3' carbon in the sugar ring of one nucleotide to the 5' carbon on the next nucleotide

sequence of bases constitutes the genetic information

Different pentose sugars in RNA & DNARNADNASugar carbonshave primenumbers, todistinguish themfrom atoms inbases

Nucleotides Deoxyribonucleotides

Ribonucleotides

Heterocyclic Nitrogen BasesRNADNA

DNA - POLYNUCLEOTIDE NUCLEOTIDENUCLEOSIDE PHOSPHATE

DEOXYRIBOSE GETEROCYCLIC NITROGEN BASE

ADENIN CYTOSIN GUANIN THYMINE

RNA - POLYNUCLEOTIDE NUCLEOTIDENUCLEOSIDE PHOSPHATE

RIBOSE GETEROCYCLIC NITROGEN BASE

ADENIN CYTOSIN GUANIN URACIL

Structure of Nucleic AcidOnly 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 appear in the nucleic is the coding for the information carried in the molecule. In other words, the nucleotide serve as a sort of genetic alphabet on which the structure of each protein in our bodies is encoded.

DNAIn the early 1950s, four scientists, James Watson and Francis Crick at Cambridge University and Maurice Wilkins and Rosalind Franklin at King's College, determined the true structure of DNA from data and X-ray pictures of the molecule that Franklin had taken. In 1953, Watson and Crick published a paper in the scientific journal Nature describing this research. Watson, Crick, Wilkins and Franklin had shown that not only is the DNA molecule double-stranded, but the two strands wrap around each other forming a coil, or helix.

WATSON-CRICK MODELCombination of two single strandsThe Double HelixSugar-phosphate backbone outside, bases inside1953

WATSON-CRICK MODELBases form specific base pairs, held together by hydrogen bondsStructure compatible with any sequence of bases

WATSON-CRICK MODELThe nucleotide bases of the DNA molecule form complementary pairs: adenine always bonds to thymine (and vice versa) and guanine always bonds to cytosine (and vice versa). This bonding occurs across the molecule, leading to a double-stranded system

The base pairing is the key to understanding how DNA functions As a trick for remembering how the bases pair up (if symbols are arranged in alphabetical order): A C G T Adenine Cytosine Guanine Thymine

Watson-Crick base pairsHydrogen bonds are weaker than covalent bonds (eg. C-C or C-N)Covalent bonds determine structure,Weak hydrogen bonds - Stabilize double helix

Base Pairing in DNADNA samples from different cells of the same species have the same proportions of the four heterocyclic basesDNA samples from different species have different proportions of basesHuman DNA contains:30% - Adenine equal amounts 30% - Thymine A = T20% - Guanine equal amounts 20% - CytosineG = C The bases occur in pairs!!!

DNA replicationThe double-stranded DNA molecule has the unique ability that it can make exact copies of itself, or self-replicate. When more DNA is required by an organism (such as during reproduction or cell growth) the hydrogen bonds between the nucleotide bases break and the two single strands of DNA separate. New complementary bases are brought in by the cell and paired up with each of the two separate strands, thus forming two new, identical, double-stranded DNA molecules.

DNA The blueprint for the structure and functioning of our bodies is contained in the genetic material found in the nucleus. The total number of base pairs in a human cell the HUMAN GENOME is 3 billion base pairsThe genetic material (chromatin) is composed of DNA (Deoxyribonucleic acid) and proteinWhen a cell is not actively dividing, its nucleus is occupied by CROMATIN

*CHROMATIN

DNA HISTONE

Chromatin is DNA wound tightly around proteins called histones. During cell division, chromatin organizes itself into CHROMOSOMESEach chromosome contain a different DNA molecule!!!

It is a linear strand of DNA in combination with nuclear proteins

We refer to this complex of DNA and proteins as chromatin It is a linear array of genes

As a set - they are our genome

What is a chromosome?

CHROMOSOMEOrganisms differ in their number of chromosomes

64 chromosomes - 32 pairs

38 chromosomes - 19 pairs 6 chromosomes - 3 pairs

46 chromosomes - 23 pairsHeredity is encoded in DNA within the chromosomes

During cell division the DNA is duplicated so that each new cell receives a complete copyEach DNA molecule is made up of many GENESGENE is individual segment of DNA that contains the instructions that direct the synthesis of a single polypeptideWhat is a GENE?

RNARibonucleic acid, or RNA, gets its name from the sugar group in the molecule's backbone - ribose. Several important similarities and differences exist between RNA and DNA.

*DNA vs RNA DNA consists of two associated polynucleotide strands that wind together in a helical fashion. It is often described as a double helix

Most RNA is single stranded and does not form a double helix

DNA vs RNADNA CompositionDeoxyribose (a pentose = sugar with 5 carbons) Phosphoric Acid Organic (nitrogenous) bases: (Purines - Adenine and Guanine, or Pyrimidines -Cytosine and Thymine)

RNA CompositionRibose (a pentose = sugar with 5 carbons) Phosphoric Acid Organic (nitrogenous) bases:

Purines (Adenine and Guanine) and Pyrimidines (Cytosine and Uracil)

*DNA vs RNADNA CompositionThe base composition is variable, but in all cases the amount of adenine is equal to the amount of thymine (A=T). In the same manner, C=G. Consequently A+C = T+G

RNA CompositionThe rule A+C=U+G CAN'T BE APPLIED THERE because most RNA is single stranded and does not form a double helix

RNA RNA (ribonucleic acid) is the messenger of DNA within the cell.Forms of RNA direct the cell to manufacture specific enzymes and other proteinsThere are several different kinds of RNA made by the cell:mRNA - messenger RNAtRNA - transfer RNArRNA - ribosomal RNA

Central DogmaHow does the sequence of a strand of DNA correspond to the amino acid sequence of a protein? This concept is explained by the central dogma of molecular biology that deals with the detailed residue-by-residue transfer of sequential information, and states that:information cannot be transferred back from protein to either protein or nucleic acid.

In other words, 'once information gets into protein, it can't flow back to nucleic acid.'

Central DogmaEvery time a cell divides, three fundamental processes known as:ReplicationTranscriptionTranslationRNA take place in the duplication, transfer, and use of genetic information

ReplicationProcess by which copies of DNA are made when a cell divides (each of two daughter cells has the same DNA)

TranscriptionProcess by which copies the genetic information in DNA is read and used to synthesize RNACODON - in the mRNA is a series of three ribonucleotides that is a code for a specific amino acid. Example: GGU on mRNA - codon for GLYCINE

TranslationProcess by which the genetic message is decoded and used to make proteinsEvery cell contains 20 or more different tRNAs, each designed to carry a specific amino acid.A tRNA molecule is L-shaped and it is a sequence of three nucleotides called ANTICODONThe Anticodon of each tRNA is complementary to mRNA codonEx: mRNA CODON CUG tRNA ANTICODON GAC

Points to rememberNucleic Acids and their structure Nucleotide vs NucleosideDNA and RNA compositionWatson-Crick model of DNAWhat is a chromosome?What is a GENE?DNA vs RNAReplication, Transcription, Translation

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