NUCLEIC ACIDSHISTORY: Friedrich Miescher in 1869:

isolated what he called nuclein from the nuclei of pus cells

Richard Altmann in 1889:

Nuclein was shown to have acidic properties, hence it became called nucleic acid

The Tetranucleotide hypothesis:

Up to 1940 researchers were convinced that hydrolysis of nucleic acids yielded the four bases in equal amounts.

Nucleic acid was postulated to contain one of each of the four nucleotides, the tetranucleotide hypothesis.

Takahashi (1932) proposed a structure of nucleotide bases connected by phosphodiester linkages.

X-ray diffraction of DNA

NUCLEIC ACIDS:• Nucleic Acids are very long, thread-like polymers, made up of a linear array of monomers called

nucleotides.

• Nucleic acids vary in size in nature

• tRNA molecules contain as few as 80 nucleotides

• Eukaryotic chromosomes contain as many as 100,000,000 nucleotides.

Nucleic acids are molecules that store information for cellular growth and reproduction

DNA and RNA are nucleic acids, long, thread-like polymers made up of a linear array of monomers called nucleotides

Nucleic acids are biopolymers, or large biomolecules, essential for all known forms of life. Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides. Each nucleotide has three components: a 5-carbon sugar, a phosphate group, and a nitrogenous base. If the sugar is deoxyribose, the polymer is DNA. If the sugar is ribose, the polymer is RNA.

Nucleic acid sequences:

One DNA or RNA molecule differs from another primarily in the sequence of nucleotides. Nucleotide sequences are of great importance in biology since they carry the ultimate instructions that encode all biological molecules, molecular assemblies, subcellular and cellular structures, organs and organisms, and directly enable cognition, memory and behavior Enormous efforts have gone into the development of experimental methods to determine the nucleotide sequence of biological DNA and RNA molecules, and today hundreds of millions of nucleotides are sequenced daily at genome centers and smaller laboratories worldwide. In addition to maintaining the GenBank nucleic acid sequence database, the National Center for Biotechnology Information (NCBI, provides analysis and retrieval resources for the data in GenBank and other biological data made available through the NCBI Web site

TYPES OF NUCLEIC ACIDS There are two types of nucleic acids:

1. deoxyribonucleic acid (DNA) and 2. ribonucleic acid (RNA)

These are polymers consisting of long chains of monomers called nucleotides

A nucleotide consists of a nitrogenous base, pentose sugar and a phosphate group.

All nucleotides contain three components:

A nitrogen heterocyclic base A pentose sugar A phosphate residue

DNA: deoxyribonucleic acid nucleic acid that stores genetic information found in the nucleus of a mammalian cell.

DNA as genetic material: The circumstantial evidence

1. Present in all cells and virtually restricted to the nucleus

2. The amount of DNA in somatic cells (body cells) of any given species is constant (like the number of chromosomes)

3. The DNA content of gametes (sex cells) is half that of somatic cells. In cases of polyploidy (multiple sets of chromosomes) the DNA content increases by a proportional factor

4. The mutagenic effect of UV light peaks at 253.7nm. The peak for the absorption of UV light by DNA

Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms . The DNA segments carrying this genetic information are called genes. Likewise, other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life. DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are, therefore, anti-parallel. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription.

Within cells DNA is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.

TYPES OF DNA:Have three Types

A-DNA B-DNA Z-DNA

1) A- DNA: Right-handed helix Widest planes of the base pairs inclined to the helix axis 6A hole along helix axis narrow + deep major groove Wide + shallow minor groove

2) B-DNA:

i. Right-handed helix

ii. intermediate

iii. planes of the base pairs nearly perpendicular to the helix axis

iv. tiny central axis

v. wide + deep major groove

vi. narrow + deep minor groove

3) Z-DNA:

i. Left-handed helix

ii. Narrowest

iii. planes of the base pairs nearly perpendicular to the helix axis

iv. no internal spaces

v. no major groove

vi. narrow + deep minor groove

RNA ribonucleic acid

Ribonucleic acid (RNA) functions in converting genetic information from genes into the amino acid sequences of proteins. The three universal types of RNA include transfer RNA (tRNA), messenger RNA (mRNA), and ribosomal RNA (rRNA). Messenger RNA acts to carry genetic sequence information between DNA and ribosomes, directing protein synthesis. Ribosomal RNA is a major component of the ribosome, and catalyzes peptide bond formation. Transfer RNA serves as the carrier molecule for amino acids to be used in protein synthesis, and is responsible for decoding the mRNA. In addition, many other classes of RNA are now known.

3 types of RNA in a cell

I. Ribosomal RNAs (rRNA) are components of ribosomes II. Messenger RNAs (mRNA) carry genetic information

III. Transfer RNAs (tRNA) are adapter molecules in translation

1: Ribosomal RNA: Ribosomes are the sites of protein synthesis

- they consist of ribosomal DNA (65%) and proteins (35%)

- they have two subunits, a large one and a small one

2: Messenger RNA: Messenger RNA carries the genetic code to the ribosomes

- they are strands of RNA that are complementary to the DNA of the gene for the protein to be synthesized

3: Transfer RNA: Transfer RNA translates the genetic code from the messenger RNA and brings specific amino

acids to the ribosome for protein synthesis

Each amino acid is recognized by one or more specific tRNA

tRNA has a tertiary structure that is L-shaped

- one end attaches to the amino acid and the other binds to the mRNA by a 3-base complimentary sequence

RNA and Transcription:

DNA is in the nucleus

Proteins are synthesized on ribosomes in the cytoplasm

RNA carries the genetic information from the nucleus to the cytoplasm

This RNA is called messenger RNA (mRNA)

RNA StructureTranscription of a DNA molecule results in a mRNA

molecule that is single-stranded.

RNA molecules do not have a regular structure like DNA.

The structures of RNA molecules are complex and unique.

RNA molecules can base pair with complementary DNA

or RNA sequences.

G pairs with C, A pairs with U, and G pairs with U.

STRUCTURE OF NUCLEIC ACID

Nucleic acid structure refers to the structure of nucleic acids such as DNA and RNA. Chemically speaking, DNA and RNA are very similar. Nucleic acid structure is often divided into four different levels: primary, secondary, tertiary and quaternary

1: Primary structure:

Primary structure consists of a linear sequence of nucleotides that are linked together by phosphodiester bonds. It is this linear sequence of nucleotides that make up the primary structure of DNA or RNA. Nucleotides consist of 3 components:

1. Nitrogenous base1. Adenine2. Guanine3. Cytosine4. Thymine (present in DNA only)5. Uracil (present in RNA only)

2. 5-carbon sugar which is called deoxyribose (found in DNA) and ribose (found in RNA).

3. One or more phosphate groupsThe nitrogen bases adenine and guanine are purine in structure and form a glycosidic bond between their 9' nitrogen and the 1' -OH group of the deoxyribose. Cytosine, thymine and uracil are pyrimidines, hence the glycosidic bonds forms between their 1' nitrogen and the 1' -OH of the deoxyribose. For both the purine and pyrimidine bases, the phosphate group forms a bond with the deoxyribose sugar through an ester bond between one of its negatively charged oxygen groups and the 5' -OH of the sugar. The polarity in DNA and RNA is derived from the oxygen and nitrogen atoms in the backbone. Nucleic acids are formed when nucleotides come together through phosphodiester linkages between the 5' and 3' carbon atoms. A Nucleic acid sequence is the order of nucleotides within a DNA (GACT) or RNA (GACU) molecule that is determined by a series of letters. Sequences are presented from the 5' to 3' end and determine the covalent structure of the entire molecule. Sequences can be complementary to another sequence in that the base on each position is complementary as well as in the reverse order. An example of a complementary sequence to AGCT is TCGA. DNA is double-stranded containing both a sense strand and an antisense strand. Therefore, the complementary sequence will be to the sense strand.

2: Secondary structureSecondary structure is the set of interactions between bases, i.e., which parts of strands are bound to each other. In DNA double helix, the two strands of DNA are held together by hydrogen bonds. The nucleotides on one strand base pairs with the nucleotide on the other strand. The secondary structure is responsible for the shape that the nucleic acid assumes. The bases in the DNA are classified as Purines and Pyrimidines.

The purines are Adenine and Guanine. Purines consist of a double ring structure, a six membered and a five membered ring containing nitrogen. The pyrimidines are Cytosine and Thymine. It has a single ringed structure, a six membered ring containing nitrogen. A purine base always pairs with a pyrimidine base (Guanosine (G) pairs with Cytosine(C) and Adenine(A) pairs with Thymine (T) or Uracil (U)). DNA's secondary structure is predominantly determined by base-pairing of the two polynucleotide strands wrapped around each other to form a double helix. There is also a major groove and a minor groove on the double helix.

3: Tertiary structure:

Tertiary structure refers to the locations of the atoms in three-dimensional space, taking into consideration geometrical andsteric constraints. It is a higher order than the secondary structure, in which large-scale folding in a linear polymer occurs and the entire chain is folded into a specific 3-dimensional shape. There are 4 areas in which the structural forms of DNA can differ.

1. Handedness - right or left2. Length of the helix turn3. Number of base pairs per turn4. Difference in size between the major and minor grooves.

THANK You