1. Introduction to Molecular Biology

2. MOLECULAR BIOLOGY

3. 1- Nucleotides 2- DNA 3- RNA

4. NUCLEOTIDES 1- NUCLEOTIDES 1- Importance of nucleotides 2- Structure of nucleotides 3- Metabolism of nucleotides i. synthesis ii. degradation

5. nucleotides Importance of nucleotides 1- Building units for nucleic acids (DNA & RNA) 2- Other roles in metabolism & energy storage (discussed later with metabolic pathways)

6. nucleotides Structure of nucleotides Nucleotides = nitrogenous base + sugar + phosphate (1,2 or 3) Nitrogenous base = Purine OR Pyrimidine Sugar = Ribose OR Deoxyribose Purine = Adenine OR Guanine Pyrimidine = Thymine, Cytosine OR Uracil

8. PURINE RING C6C6 C5C5 N3N3 N1N1 C2C2 C4C4 N7N7 C8C8 N9N9

9. Pyrimidine RING C4C4 C5C5 N1N1 N 3 C2C2 C6C6

10. b

11. Purines : Adenine & Guanine Pyrimidines: Cytosine, Thymine & Uracil DNA contains Adenine & Guanine (purines) Cytosine & Thymine (pyrimidines) RNA contains Adenine & Guanine (purines) Cytosine & Uracil (pyrimidines)

12. Metabolism of nucleotides 1- Synthesis (anabolism) i. sources of purine ring atoms ii. sources of pyrimidine ring atoms 2- Degradation (catabolism) i. end products of purine ring ii. end product of pyrimidine ring

13. Synthesis of purines: Synthesis of purines: Sources of atoms of purine ring

14. Synthesis of pyrimidines Synthesis of pyrimidines: Sources of atoms of pyrimidine ring

15. Degradation (catabolism) Degradation (catabolism): End products of purine ring degradation In human cells purine nucleotides is finally degraded to URIC ACID Uric acid is transported in blood to kidneys Finally, Uric acid is excreted in urine If uric acid is increased in blood --- HYPERURICEMIA (CAUSES??) Hyperuricemia may lead to --------- GOUT GOUT is a disease affects joints (arthritis) & kidneys (kidney stones) caused by deposition of uric acid in tissues

16. Pyrimidine nucleotides are degraded to highly soluble products : -alanine & -aminoisobutyrate Degradation (catabolism): End products of pyrimidine ring degradation

17. DNA 1- Importance of DNA 2- Location of DNA in human cells 3- Structure of DNA molecule - Structure of a single strand of DNA - Structure of double stranded DNA - Linear & circular DNA

18. DNA Importance of DNA 1- Storage of genetic material & information (material of GENES) 2- Transformation of genetic information to new cells (template for REPLICATION) i.e. synthesis of new DNA for new cells 3- Transformation of information for protein synthesis in cytosol (template for TRANSCRIPTION) i.e. synthesis of mRNA in nucleus

19. Structure of DNA molecule

20. Structure of Single strand of DNA Building Units: Polynucleotide sugar: deoxyribose Purine: A & G Pyrimidine: T & C Polynucleotides are bound together by phosphodiester bonds If linear DNA: two ends (5` = phosphate & 3` = OH of deoxyribose) If circular: no ends Sequence of DNA

21. Structure of double stranded DNA Two strands are anti-parallel (in opposite directions) Hydrogen bonds between bases of opposite strands (A & T, C & G) Denaturation = breakdown (loss) of hydrogen bonds between two strands (melting) leading to formation of two separate single strands) Causes of denaturation ?? IMPORTANCE ?? e.g. PCR heating or change of pH of DNA

22. Linear & Circular DNA 1- Linear DNA in nucleus of eukaryotes (include. Human cells) i.e. chromosomes 2- Circular DNA i. in eukaryotes: mitochondria ii. in prokaryotic chromosomes (nucleoid of bacteria) iii. in plasmids of bacteria (extrachromosomal element) IMPORTANCE ?? iv. in plant chroroplasts

23. Replication Semiconservative replication When the two strands of the DNA double helix are separated, each can serve as a template for the replication of a new complementary strand. Each of the individual parental strands remains intact in one of the two new Duplexes (i.e. one of the parental strands is conserved in each of the two new dublexes)

24. RNA Structure 1- Structure (differences from DNA) Types 3- Types Importance of each type 4- Importance of each type

25. RNA Structure of RNA Building units: Polynucleotides (bound together by PDE) Single strand Linear (but may fold into complex structure) with two ends: 5`(phosphate) & 3`(-OH end) Sugar: Ribose Purine bases: Adenine & Guanine Pyrimidine bases: Cytosine & Uracil

26. RNA Types & Functions of RNA

27. Ribosomal RNA (rRNA) 80% of total RNA in the cell (most abundant RNA) Location: cytosol Function : machine for protein biosynthesis Types:

28. Transfer RNA (tRNA) Smallest of RNAs in cell: 4S Location: cytosol At least one specific tRNA for each of the 20 amino acids found in proteins with some unusual bases with intrachain base-pairing (to provide the folding structure of tRNA) Function: 1- recognizes genetic code word on mRNA 2- then, carries its specific amino acid for protein biosynthesis

29. synthesized in the nucleus (by transcription): DNA (the gene) is used a template for mRNA synthesis mRNA is synthesized complementary to DNA but in RNA language i.e. U instead of T So, if A in DNA it will be U in RNA, if T in DNA it will be A in mRNA….etc Carries the genetic information from the nuclear DNA (gene) to the cytosol In the cytosol, mRNA is used as a template for protein biosynthesis by ribosomes (with help of tRNA)…. This is called Translation or Protein Biosynthesis) Transcription + Translation = GENE EXPRESSION Messenger RNA (mRNA)

30. complementary base-pair between DNA & RNA in transcription

31. Types of mRNA Polycistronic mRNA:Polycistronic mRNA: One single mRNA strand carries information from more than one gene (in prokaryotes) Monocistronic mRNA:Monocistronic mRNA: one single mRNA strand carries information from only one gene (in eukaryotes)

32. Eukaryotic mRNA 5`-end: cap of 7-methylguanosine 3`-end: poly-A tail

33. The Genetic Code is a dictionary that identifies the correspondence between a sequence of nucleotide bases & a sequence of amino acids Each individual word of the code is called a codon a codon is composed three nucleotide bases in mRNA language (A, G, C & U) in 5`-3` direction e.g. 5`-AUG-3` The four bases are used by three at a time to produce 64 different combinations of bases 61 codons: code for the 20 common amino acids 3 codons UAG, UGA & UAA: do not code for amino acids but are termination (stop) codons

34. Genetic Code Table