BTY 100 Lec4 1 Genetic Basis of Life

BTY 100 -Lec#4. 1 Genetic Basis of Life Genetic Makeup © LPU: BTY 100

Outline Genetic Material DNA RNA Structure DNA and RNA comparison Central Dogma © LPU: BTY 100

Every human creation comes with some specifications which are found on a particular location. These specifications are basically information © LPU: BTY 100

All Information in ATGC…. . really Just like a computer stores How? ? ? all its information in 0 and 1 (Binary Language) all human information is stored in Genetic Language which is having only 4 alphabets (ATGC). These alphabets are stored in our Genetic Material © LPU: BTY 100 DNA and RNA

The Genetic Material DNA and RNA Genetic material refers to the material that determines the inherited characteristics of a functional organism. It plays a fundamental role in determining the nature and structure of a cell. It can either be DNA or RNA. © LPU: BTY 100

Blue Print of life Most stable structure Information Storage Unit of Life © LPU: BTY 100

Different features © LPU: BTY 100

All these difference are because of different information stored in your DNA. © LPU: BTY 100

• 99. 9% of all human DNA is the same; only 0. 1% is different in each person. • This 0. 1 % different makes us so different from other. • Observe your friends around you……. . © LPU: BTY 100

Where is DNA located? © LPU: BTY 100

DNA molecule DNA is a very large molecule made up of a long chain of sub-units The sub-units are called nucleotides Each nucleotide is made up of A sugar- Deoxyribose An nitrogenous base (A T G C ) A phosphate group -PO 4 and © LPU: BTY 100

4 THE SUGARS: RIBOSE & DEOXYRIBOSE Ribose is a sugar, with only five carbon atoms in its molecule Deoxyribose is almost the same but lacks one oxygen atom at C 2 Both molecules may be represented by the symbol © LPU: BTY 100

Organic Bases The nucleotide bases found in nucleic acids are related either to the purine or pyrimidine ring system. Both DNA and RNA contain two major purine bases, adenine (A) and guanine (G), and two major pyrimidines. In both DNA and RNA one of the pyrimidines is cytosine (C), but the second major pyrimidine is not the same in both: it is thymine (T) in DNA and uracil (U) in RNA.

Nitrogenous Bases of DNA Pyrimidines Single Ringed © LPU: BTY 100 Purines Double Ringed

Purines V/S Pyrimidines © LPU: BTY 100

Nucleoside and Nucleotide • Nucleotides Are the Monomeric Units of Nucleic Acids • A unit consisting of a base bonded to a sugar is referred to as a nucleoside. • A nucleotide is a nucleoside joined to one or more phosphate groups by an ester linkage

Nucleoside and Nucleotide © LPU: BTY 100

PHOSPHODIESTER LINKAGE • These nucleotides are joined together to form Chains of Nucleic acids. • This linkage between the nucleotides is known as Phosphodiester Linkage. • The successive nucleotides of both DNA and RNA are covalently linked through phosphate-group “bridges, ” in which the 5’-phosphate group of one nucleotide unit is joined to the 3 -hydroxyl group of the next nucleotide, creating a Phosphodiester linkage © LPU: BTY 100

Phosphodiester Linkage © LPU: BTY 100

The chain has a 5 end, which is usually attached to a phosphate, and a 3 end, which is usually a free hydroxyl group. This forms the sugarphosphate backbone of one DNA strand.

From Single Strand to Double Strand • DNA molecules are double stranded. • The sugar-phosphate chains are on the outside and the strands are held together by chemical bonds between the bases. • The formation of hydrogen bonds between the bases takes place according to Chargaff’s Rule. © LPU: BTY 100

CHARGAFFS RULE: • “It states that DNA from any cell of all organisms should have a 1: 1 ratio of pyrimidine and purine bases and more specifically that the amount of guanine is equal to amount of cytosine and amount of adenine is equal to amount of thymine” • %A=%T • %G=%C • %(A+G)= %(T+C)

Rule of Complementary Base pairing: • Adenine and Thymine always join together A T • Cytosine and Guanine always join together C G © LPU: BTY 100

COMPLEMENTARY NATURE OF DNA The two strands of DNA are complementary to one another because of the properties of base pairing: A will only pair with T by two hydrogen bonds G will only pair with C by three hydrogen bonds © LPU: BTY 100

Base pairing rules © LPU: BTY 100 A T G C

ANTIPARALLEL NATURE • The two strands of DNA are also antiparallel(run in opposite directions) to one another. • A strand of DNA can have the direction 5'-3' or 3'- 5'. • One strand in the DNA molecule is 5'-3' and the other strand is 3'-5'.

DNA Structure James Watson and Francis Crick worked out the 3 D structure of DNA, based on work by Rosalind Franklin. © LPU: BTY 100

DNA is Double Helical Structure © LPU: BTY 100

Watson and Crick Model of DNA Double Helix Draw the diagram © LPU: BTY

• The two strands run antiparallely and are complimentary to each other. • The coiling is right handed. • The major groove occurs where the backbones are far apart, the minor groove occurs where they are close together. • The sugar-phosphate backbones are on the outside and, therefore, the purine and pyrimidine bases lie on the inside of the helix. Adenine always pairs with Thymine, Guanine binds with Cytosine • The bases are nearly perpendicular to the helix axis, and adjacent bases are separated by 3. 4 Å. • The helical structure repeats every 34 Å, so there are 10 bases (= 34 Å per repeat/3. 4 Å per base) per turn of helix. • There is a rotation of 36 degrees per base (360 degrees per full turn/10 bases per turn). • The diameter of the helix is 20 Å.

RNA is also a nucleic acid The bridge between DNA and protein synthesis is the nucleic acid RNA. Different sugar, U instead of T, Single strand, usually Nitrogenous base (A, G, C, or U) Phosphate group RNA is made of ribonucleic acids instead of deoxyribonucleic acids • RNA is single-stranded • In RNA sequences, Thymine (T) is replaced by Uracil (U) m. RNA carries the message from genome to proteins © LPU: BTY 100 Sugar (ribose)

Character RNA DNA Nitrogenous bases RNA contains adenine, uracil, cytosine, and guanine. DNA contain adenine, thymine, cytosine, guanine; Strandedness RNA is single-stranded. DNA is double-stranded Location RNA can be found in both the nucleus and cytoplasm. DNA is only found in the nucleus Functions RNA carries out protein synthesis. RNA transfers the information to other places in the cell DNA contains the information for protein synthesis. DNA stores genetic information Pentose sugar Hydroxyl group present at Absence of hydroxyl 2 carbon of the pentose group at 2 C of the sugar pentose sugar