this presentation covers about all the topics of nucleic acids.I made this presentation by combining too many presentations. and I also presented the same in the university and I got an A++ :).
this presentation covers about all the topics of nucleic acids.I made this presentation by combining too many presentations. and I also presented the same in the university and I got an A++ :).
best of luck!
Introduction: Frederic Miesher in 1869, isolated an acidic compound from the nuclear material of SALMON sperms, and named it as NUCLIEN which is now called NUCLEIC ACID. Jones in 1920 proved the fact there are two types of nucleic acids, i.e., Deoxyribo nucleic acid (DNA) and Ribonucleic acid (RNA). In 1935 J. D. Watson and F. H. C Crick, on the basis of information's available not only proposed the “Double helical” structure of DNA but also suggested what Crick termed “central dogma of molecular genetics”, which states that genetic information flows from DNA to RNA to protein.
Central Dogma DNA RNA amino acids proteins
CENTRAL DOGME : 1.Replication:The copying of the DNA to form identical daughter molecules. 2. Transcription :The process by which the genetic message in DNA is transcribed in the form of m RNA to be carried to the ribosome 3.Translation: The process by which the message is decode by the ribosome's, where m RNA is used as a template in directing the specific amino acids sequence during protein biosynthesis.
Nucleic acids Two types; DNA RNA The building blocks of nucleic acids are called NUCLEOTIDES
Nucleic Acids Chemical Composition Elements: C, H, O, N, and P. There are 2 types of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Nucleotide Nucleotides: monomers of nucleic acids. All nucleic acids consist of many nucleotides bonded together. Nucleic acids are polynucleotide. Their building blocks are nucleotides
Monomers nucleotides, are made up of three parts: (a) Phosphate (phosphoric acid) (b) N-base (Nitrogenous base) (c) Sugar ~ ribose or deoxyribose
Adenine Thymine Guanine Cytosine The bases always pair up in the same way A purine with a pyrimidine Adenine forms a bond with Thymine and Cytosine bonds with Guanine
DNA Structure Sugar= Deoxyribose Specific Base Pairing Adenine-Thymine Guanine-Cytosine Forms a double Helix Structure
RNA structure Sugar= Ribose Thymine gets replaced by Uracil Single stranded
Structural (and functional) Comparison of DNA & RNA Structural (and functional) Comparison of DNA & RNA
Functions DNA is used to store genetic information It is replicated before cell division DNA is very important so it is stored in the nucleus. It never leaves the nucleus Your DNA stores the code for your proteins, which exhibit your “traits” The DNA gets converted to RNA in order to move out into the cytoplasm
Functions In the cytoplasm it meets up with the ribosome, where it can synthesize proteins Stores genetic information. Maintains growth and repair. Controls all cellular activities. Contains protein codes. Ensures each daughter cell & gamete receives exact genetic information.
Nucleic Acid: Nucleic acids are non-proreinnirogeneous bases made up of Monomeric units called nucleotides. These are molecules through which organisms are described through their continuation. TYPESOFNUCLEICACIDS: DNA RNA
DNA : Abbreviation of deoxyribonucleic acid. It is a polymer of Deoxyribo nucleotide. This thread like structure is a combination of large number of nucleotide units joined together. This Polynucleotide contains genetic information that gives rise to chemical and physical properties of organisms.
Location and Isolation: LOCATION: It can be found in chromosomes (specifically nucleus), mitochondria and chloroplast of the cell. It is present in every living organism because it contains genetic material. ISOLATION: From viruses, bacteria, thymus gland, spleen, blood, hair, skin, etc
Size of DNA: Size shows great variation. Only 1.7µm long in simple structure of simian virus with 5 or 6 genes. and can also extend to 2M in Human DNA. The size of human DNA inside the chromosome is just 200 nm.
The sub-units are called nucleotides Each nucleotide is made up of a pentose sugar calleddeoxyribose a phosphate group -PO4 and Nitrogenous bases DNA is a very large molecule made up of a long chain of sub-units
Deoxyribose Deoxyriboseis almost the same as RNA but lacks one oxygen atom
Phosphate Group : Negatively charged Phosphate group is present to whole positively charged protein molecule. O P O O O
Structure of the DNA-continued c. Nitrogenous base: There are four different bases which are divided into two groups. i) Pyrimidines: These are single rings each with six sides. They are Cytosine and Thymine . ii) Purines: These are double rings comprising a six-sided and a five-sided ring. They are Adenine and Guanine.
Adenine always pairs with Thymine, with the help of two hydrogen bonds and Guanine always pairs with Cytosine with the help of three hydrogen bonds. This makes the two chains complimentary to each other.
The bases Adenine (A) Thymine (T) Cytosine (C) (G) Guanine The most common organic bases are
Nucleotides The deoxyribose, the phosphate and one of the bases Combine to form a nucleotide PO4 adenine deoxyribose
Joined nucleotides PO4 PO4 PO4 PO4 A molecule of DNA (polymer) is formed by millions of nucleotides joined together by phospodiester bonds into a long chain by condensation reactions. sugar-phosphate backbone + bases
In fact, the DNA usually consists of a double strand of nucleotides The sugar-phosphate chains are on the outside and the strands are held together by hydrogen bonds between the bases
Types of DNA : Two types; Circular DNA Non-Circular DNA CIRCULAR DNA : In Eukaryotes: The ends of DNA are cohesive,so they join forming a circular DNA.eg.mitochondria,chloroplast,tec. In Prokaryotes: mostly it is in the form of PLASMID whose replication donot depends on genomic DNA.eg.bacteria.
NON-CIRCULAR DNA: The two anti parallel strands of DNA twist around each other to form helical structure of double helix.
FUNCTIONS OF DNA DNA has 2 major functions: 1. Replication in dividing cells, allowing accurate copying of DNA for cell division. 2. Carrying the information for protein synthesis in all cells.
Steps of DNA Replication 1) DNA must unwind and break the hydrogen bonds 2) Each strand is used as a template (blueprint) 3) Two new strands of DNA are formed from the original strand by the enzyme DNA Polymerase
During replication, an enzyme called helicase “unzips” the DNA molecule along the base pairing, straight down the middle. Another enzyme, called DNA polymerase, moves along the bases on each of the unzipped halves and connects complementary nucleotides. What do we mean by complementary nucleotides?
Original strand New strand DNA polymerase DNA polymerase Growth Growth Nitrogenous bases Replication fork Replication fork New strand Original strand
Because of Chargaff’s rule, only the correct, complementary bases will fit, so chances are good that the DNA polymerase will make a perfect copy. Mistakes happen! Mutation! Is this frog likely to survive long in the wild?
Transcription- how RNA is made Just as DNA polymerase makes new DNA, a similar enzyme called RNA polymerase makes new RNA. RNA polymerase temporarily separates the strands of a small section of the DNA molecule. This exposes some of the bases of the DNA molecule. Along one strand, the RNA polymerase binds complementary RNA nucleotides to the exposed DNA bases. An exposed thymine on the DNA strand hooks up with an RNA nucleotide with an adenine; an exposed cytosine on the DNA hooks up with an RNA nucleotide with a guanine base; an exposed adenine DNA base will hook up with URACIL!
As the RNA polymerase moves along, it makes a strand of messenger RNA (mRNA). It is called messenger RNA because it carries DNA’s message out of the nucleus and into the cytoplasm. mRNA is SINGLE STRANDED! When the RNA polymerase is done reading the gene in the DNA, it leaves. The separated DNA strands reconnect, ready to be read again when necessary. mRNA moves out of the nucleus and finds a ribosome On the ribosome, amino acids are assembled to form proteins in the process called translation.
HISTORY OF DNA : Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
Griffith’s Experiment Was trying to develop a vaccination for the pneumococcus bacteria. Vaccine- a prepared substance from killed or weakened disease causing agents used to prevent future infections He was working with two strains of bacteria. Rough - bacteria had a rough appearance in culture, non-virulent (doesn't kill) Smooth - bacteria had a smooth appearance in culture, virulent (kills)
Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control(no growth) Lives Dies of pneumonia Lives Dies of pneumonia Live, disease-causingbacteria (smooth colonies)
DNA as hereditary material The Genetic Material is DNA – Alfred Hershey and Martha Chase, 1952 Previously, scientists thought that proteins were the hereditary molecule Hershey and Chase worked with viruses that infect bacteria called bacteriophages Through a series of experiments, they were able to show that DNA, not protein, is the hereditary molecule.
Hershey – Chase Experiment – DNA in Viruses Radioactivity inside bacterium Phage infectsbacterium Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Bacteriophage with sulfur-35 in protein coat No radioactivity inside bacterium
Hershey & Chase Experiment Concluded that the DNA of viruses is injected into the bacterial cells, while the viral proteins remain outside The injected DNA molecules cause the bacterial cells to produce more viruses DNA is the hereditary material – not proteins.
Wilkins and Rosalind Franklin M.H.F. Wilkins and Rosalind Franklin, early 50’s Wilkins and Franklin studied the structure of DNA crystals using X-rays. They found that the crystals contain regularly repeating subunits. The X pattern produced by DNA suggested that DNA contains structures with dimensions of 2 nm, 0.34 nm, and 3.4 nm. The dark structures at the top and bottom indicate that some structure was repeated, suggesting a helix.
Rosalind Franklin X-ray diffraction image of DNA
Watson and Crick James Watson and Francis H.C. Crick, 1953 Watson and Crick used Chargaff's base data and Franklin’s X-ray diffraction data to construct a model of DNA. The model showed that DNA is a double helix with sugar-phosphate backbones on the outside and the paired nucleotide bases on the inside, in a structure that fit the spacing estimates from the X-ray diffraction data. Chargaff's rules showed that A = T and G = C, so there was complementary base pairing of a purine with a pyrimidine, giving the correct width for the helix. The paired bases can occur in any order, giving an overwhelming diversity of sequences.
Chargaff’s rules: Base pairing rule is A-T and G-C Thymine is replaced by Uracil in RNA Bases are bonded to each other by Hydrogen bonds Discovered because of the relative percent of each base; (notice that A-T is similar and C-G are similar)
Nucleosome Chromosome DNA double helix Coils Supercoils Histones
FUNCTIONS OF DNA : -Stores genetic information. -Maintains growth and repair. -Controls all cellular activities. -Contains protein codes. -Ensures each daughter cell & gamete receives exact genetic information.
INTRODUCTION: Ribonucleic acid usually called as RNA, is a biologically important type of molecule that consists of a long chain of nucleotide units. It is a single stranded chain of nucleotides that contains genetic information and it functions for the synthesis of proteins and also to transfer genetic information from one generation to the next.
HISTORY OF RNA : Nucleic acids were discovered in 1868 by Friedrich Miescher, who called the material 'nuclein' since it was found in the Nucleus. Nuclein was shown to have acidic properties, hence it became called nucleic acid The role of RNA in protein synthesis was suspected already in 1939.
Severo Ochoa won the 1959 Nobel Prize in Medicine after he discovered how RNA is synthesized. Carl Woese realized RNA can be catalytic in 1967 and proposed that the earliest forms of life relied on RNA both to carry genetic information and to catalyze biochemical reactions—an RNA world. In 1990 it was found that introduced genes can silence homologous endogenous genes in plants, now known to be a result of RNA interference. In same year, the discovery of gene regulatory RNAs has led to attempts to develop drugs made of RNA, like siRNA, to silence genes.
STRUCTURE OF RNA : Found in the nucleus and cytoplasm. Linear, single strandof nucleotides. Contains the sugar, ribose. N-bases include adenine, uracil, cytosine and guanine. Backbone is of ribose sugar-phosphate.
The sub-units are called nucleotides Each nucleotide is made up of a pentose sugar called ribose a phosphate group -PO4 and anitrogenous base RNA is a large molecule made up of a long chain of sub-units *RNA structure: single-strand molecule Note: Backbone consists of alternating P-S-P-S-P- etc…
Ribose Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule
The bases Adenine (A) Uracil (U) Cytosine (C) (G) Guanine The most common organic bases are
Nucleotides The deoxyribose, the phosphate and one of the bases Combine to form a nucleotide PO4 adenine ribose
PO4 PO4 PO4 PO4 Joined nucleotides A molecule of RNA is formed by millions of nucleotides joined together into a long chain . sugar-phosphate backbone + bases
Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes RNA can be also called which functions to also called also called which functions to from to to make up
Messenger RNA : Also known as mRNA. Messenger RNA is a single long chain of nucleotides It is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA istranscribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes.
WORKING OF MRNA : In mRNA as in DNA, genetic information is encoded in the sequence of nucleotides arranged into codons consisting of three bases each. Each codon encodes for a specific amino acid, except the stop codons that terminate protein synthesis.
RIBOSOMAL RNA : It is also known as rRna. Ribosomal RNA is the central component of the ribosome, the protein manufacturing machinery of all living cells.
Ribosomal RNA - continued Ribosomal RNA has two units, one large and the other small. . Ribosomal RNA Large subunit (rRNA) Small subunit
The function of the rRNA is to provide a mechanism for decoding mRNA into amino acids and to interact with the tRNAs during translation. The tRNA then brings the necessary amino acids corresponding to the appropriate mRNA codon.
Working mRNA is sandwiched between the small and large subunits and the ribosome catalyzes the formation of a peptide bond between the 2 amino acids that are contained in the rRNA. The ribosome also has 3 binding sites called A, P, and E. The A site in the ribosome binds to an aminoacyl-tRNA (a tRNA bound to an amino acid).
The amino (NH2) group of the aminoacyl-tRNA, which contains the new amino acid, attacks the ester linkage of peptidyl-tRNA (contained within the P site), which contains the last amino acid of the growing chain, forming a new peptide bond. The tRNA that was holding on the last amino acid is moved to the E site, and what used to be the aminoacyl-tRNA is now the peptidyl-tRNA. A single mRNA can be translated simultaneously by multiple ribosomes.
TRANSFER RNA : Transfer RNA (abbreviated tRNA) is a small RNA molecule (usually about 74-95 nucleotides) that transfers a specific active amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. act as adapter between nucleotides codons and amino acids. They pick up free amino acids in cytoplasm and carry them into the ribosomes where polypeptide chain is elongated.
Transfer RNA Each tRNA carries an amino acid As each codon of the mRNA molecule moves through the ribosome, the corresponding amino acid is brought into the ribosome by the tRNA. Each tRNA molecule has three unpaired bases (anticodons)which are complimentary to mRNA codons
There are 20 different tRNAs, for the different aminoacids.
Differences between DNA and RNA DNA RNA Structure: Double stranded Sugar: Deoxyribose Bases: Adenine Guanine Cytosine Thymine Structure: Single-stranded Sugar: Ribose Bases: Adenine Guanine Cytosine Uracil
Why are proteins needed? Immune system Muscles move bones Cell membranes Enzymes For repair of broken cells Growth of organisms
Decoding the Information in DNA How does DNA (a twisted latter of atoms) control everything in a cell and ultimately an organism? DNA controls the manufacture of all cellular proteins including enzymes A gene is a region of DNA that contains the instructions for the manufacture of on particular polypeptide chain (chain of amino acids) DNA is a set of blueprints or code from making proteins
How do you get from DNA to Proteins? TRANSCRIPTION – the synthesis of RNA under the direction of DNA TRANSLATION – the actual synthesis of a protein, which occurs under the direction of mRNA
Where does this happen? Where is the DNA? Protein synthesis – the manufacture of proteins Where are proteins made in the cell?
Translation: Protein Synthesis mRNA combines with a ribosome and tRNA and makes a protein Remember: mRNA carries the codon (three base sequence that codes for an amino acid) tRNA carries the anticodon which pairs up with the codon tRNA brings the correct amino acid by reading the genetic code
tRNA (transfer RNA) tRNA carries (or transfers) the correct amino acid to the codon on the mRNA. tRNA has an ANTICODON that can attach to mRNA’s codon.
SO: Say the mRNA strand reads: mRNA (codon) AUG–GAC–CAG-UGA tRNA (anticodon) UAC-CUG-GUC-ACU tRNA would bring the amino acids: Methionine-Aspartic acid-Glutamine-stop
1)mRNA is transcribed in the nucleus and leaves the nucleus to the cytoplasm 2) mRNA attaches to the ribosome 3)The codon on the mRNA is read by the anticodon on the tRNA 4) tRNA brings the amino acid as it reads mRNA 5) The amino acids are joined together to form a polypeptide (protein) 6) When a stop codon is reached (UAA, UAG, UGA) protein synthesis stops
What if things go wrong? MUTATION!!! If transcription or translation were to copy the wrong sequence, the incorrect amino acid could be added This would change the overall protein structure and could make the protein ineffective Sickle cell anemiais caused by a single amino acid difference in the hemoglobin protein sequence
Gene Mutations Point Mutations – only occur at a single point in the DNA sequence – only changes a few amino acids Frameshift Mutations – shift the entire “reading frame” – change ALL the amino acids
Mutations Substitution – one base replaces another Insertion – an extra base is inserted Deletion – loss of a single letter (makes entire base disappear!)
Chromosomal Mutations Change in the number or structure of chromosomes Ex. – Deletion, Duplication, Inversion, and Translocation