1. DNA and RNA structure
The painting “Dawn of the Double Helix” composes the DNA duplex as human figures. The theme in this painting is “Life forms: The basic structures that make our existence possible”.

2. Two types of nucleic acids – DNA and RNA
Genome - the genetic information of an organism. The genomes of all cells are composed of DNA.
Nucleic acids are biopolymers consisting of nucleotides
Nucleotides have three components: (1) A weakly basic nitrogen base (2) A five-carbon sugar (3) Phosphate

3. Ribose and Deoxyribose
Рибоза
Дезоксірибоза
Ribose is the constituent of RNA
Deoxyribose is the constituent of DNA

4. Nitrogen Bases of Nucleic Acids
Adenine
Guanine
Cytosine
Thymine
Uracil
The nitrogen bases are derivatives of either pyrimidine or purine.

5. Nucleosides
Nucleosides are composed of ribose or deoxyribose and a heterocyclic base.

6. Structure of mononucleotide
Adenosine mononucleotide

7. Formation of DNA chain (5’-3’ direction)

8. Nucleotides joined by 3’-5’ phosphodi-ester linkages
One end of the polynucleotide chain is said to be 5’ (no residues are attached to 5’-carbon) and other is said to be 3’. Direction from the top to bottom is called 5’→3’, from bottom to top – 3’→5.

9. Primary structure of nucleic acids

10. Two Antiparallel Strands Form a Double Helix
DNA is Double-Stranded
Two Antiparallel Strands Form a Double Helix
Two strands run in opposite directions
Bases in opposite strands pair by complementary hydrogen bonding
Adenine (A) Thymine (T)
Guanine (G) Cytosine (C)
Crick Francis
Watson James
The double helix of DNA was discovered in by Crick F. and Watson J. Nobel prize in 1962.

11. Chemical structure of double-stranded DNA
Chemical structure of double-stranded DNA. The two strands run in opposite directions. Adenine in one strand pairs with thymine in the opposite strand, and guanine pairs with cytosine

12. Comple-mentary base pairing and stacking in DNA

13. Two-stranded struc-ture of DNA

14. DNA in cells is a constituent of chromatin
Chromatin – DNA plus different proteins
Histones – main proteins of chromatin

15. Chromatin structure
DNA is packaged by coiling into a solenoid (helix) structure

16. Types of RNA (1) Transfer RNA (tRNA)
Carries amino acids to translation machinery
Very stable molecules
(2) Ribosomal RNA (rRNA)
Makes up much of the ribosome
Very stable, majority of cellular RNA
(3) Messenger RNA (mRNA)
Encodes message from DNA to ribosomes
Rapidly degraded by nucleases

17. DNA Replication

18. The flow of genetic information in a typical cell
The main postulate of molecular biology
DNA 
RNA
protein

19. Replication – synthesis of DNA on the DNA template
Semiconservative mechanism of DNA replication
The two strands separate, and each strand is copied to generate a comple-mentary strand Each parental strand remains associated with its newly synthesized complement, so each DNA duplex contains one parental strand and one new strand.

20. A model for DNA replication

21. Components which are necessary for replication
Enzymes (most important – DNA-dependent DNA polymerase)
Protein factors
Parental DNA
ATP, GTP, ТТP, CТP
Ions Mg і Zn

22. DNA replication
In eukaryotes the replication begins in many points simultaneously
V-shape – replication forks - the point of the beginning of replication
Helicase – enzyme untwisting the double strand 5’ 3’
Helicase
Primase 5’
Okazaki fragments 3’
Primer
Leading strand
Lagging strand 5’ 3’

23. Replisome - protein machinery for replication
Replisome contains: primosome, DNA polymerase III, proteins
Helicase is a constituent of primosome

24. Bidirectional DNA replication in E. coli
New strands of DNA are synthesized at the two replication forks where replisomes are located

25. DNA polymerase
DNA polymerase III – the main enzyme of replication responsible for the chain elongation
Appropriate nucleotides are inserted in the correct positions according to the complementary principle
DNA polymerases only synthesize new strand in the 5’-3’ direction.

27. Direction of synthesis 5’-3’, antiparalelly to matrix chain

28. DNA polymerase synthesizes two strands simultaneously
Because DNA polymerases only polymerize nucleotides 5 ’3’, both strands must be synthesized in the 5’3’ direction. Thus, the copy of the parental 3’5’ strand is synthesized continuously; this newly made strand is designated the leading strand. As the helix unwinds, the other parental strand (the 5’3’, strand) is copied in a discontinuous fashion through synthesis of a series of fragments - Okazaki fragments; the strand constructed from the Okazaki fragments is called the lagging strands

29. Синтез відстаючого ланцюга відбувається дискретно
Lagging strand is copied in a discontinuous fashion (Okazaki fragments)
The formation of a phosphodi-ester linkage between of adjacent Okazaki fragments is catalized by ligase

30. Okazaki Model
Reiji Okazaki provided experimental evidence for discontinuous DNA synthesis

31. RNA Primer Begins Each Okazaki Fragment
Primosome is a complex containing primase enzyme which synthesizes short pieces of RNA at the replication fork - primer
DNA pol III uses the RNA primer to start the lagging-strand DNA synthesis
Replisome - includes primosome, DNA pol III
Each Okazaki fragment has the primer

32. DNA polymerase I activities
Okazaki Fragments Are Joined by Action of DNA Polymerase I and DNA Ligase
DNA polymerase I activities
DNA pol I removes the RNA primer at the beginning of each Okazaki fragment
Synthesizes DNA in place of RNA
DNA ligase
Catalyzes the formation of a phosphodiester linkage between of adjacent Okazaki fragments

33. Repair of Damaged DNA
DNA is the only cellular macromolecule that can be repaired
DNA damage includes: -base modifications -nucleotide deletions or insertions -cross-linking of DNA strands -breakage of phosphodiester backbone

34. Reparation – enzymatic deletion and synthesis of the damaged DNA fragments
Recombination - exchange or transfer of pieces of DNA from one chromosome to another or within a chromosome
Transposition – dislocation of gene or group of genes from one place to another