1. Nucleic Acids

2. Nucleic acids
DNA and RNA are chemical carriers of a cell’s genetic information
Coded in a cell’s DNA is the information that determines the nature of the cell, controls cell growth, division
Nucleic acid derivatives are involved as phosphorylating agents in biochemical pathways

3. Ribose is a sugar, like glucose, but with only five
Ribose & deoxyribose 4
Ribose is a sugar, like glucose, but with only five
carbon atoms in its molecule
Deoxyribose is almost the same but lacks one
oxygen atom
Both molecules may be represented by the symbol

4. 5 The bases The most common organic bases are Adenine (A) Thymine (T)
Cytosine
(C)
Guanine
(G)

5. Combine to form a nucleotide
Nucleotides 6
The ribose, the phosphate and
one of the bases
Combine to form a nucleotide
bases
ribose
PO4
It is the phosphate group which gives DNA its acidic properties

6. Heterocycles in DNA and RNA
Adenine, guanine, cytosine and thymine are in DNA
RNA contains uracil rather than thymine

7. Nucleotides and Nucleic Acids
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are the chemical carriers of genetic information
Nucleic acids are biopolymers made of nucleotides, aldopentoses linked to a purine or pyrimidine and a phosphate
RNA is derived from ribose
DNA is from 2-deoxyribose
(the ' is used to refer to positions on the sugar portion of a nucleotide)

8. Nucleosides in DNA Base Sugar Nucleoside
Adenine (A) Deoxyribose Adenosine
Guanine (G) Deoxyribose Guanosine
Cytosine (C) Deoxyribose Cytidine
Thymine (T) Deoxyribose Thymidine

9. Nucleosides in RNA Base Sugar Nucleoside Adenine (A) ribose Adenosine
Guanine (G) ribose Guanosine
Cytosine (C) ribose Cytidine
Uracil (U) ribose Uridine

10. Nucleotides
Nucleic acids consist of nucleotides that have a sugar, nitrogen base, and phosphate
nucleoside
Base
PO4
Sugar

11. Example of a Nucleoside

12. Nucleotides
In DNA and RNA the heterocycle is bonded to C1 of the sugar and the phosphate is bonded to C5 (and connected to 3’ of the next unit)

14. Nucleotides join together in DNA and RNA by as phosphate between the 5’-on one nucleotide and the 3 on another
One end of the nucleic acid polymer has a free hydroxyl at C3 (the 3 end), and the other end has a phosphate at C5 (the 5 end).

15. Nucleotides in DNA and RNA
dAMP Deoxyadenosine monophosphate
dGMP Deoxyguanosine monophosphate
dCMP Deoxycytidine monophosphate
dTMP Deoxythymidine monophosphate
RNA
AMP adenosine monophosphate
GMP guanosine monophosphate
CMP cytidine monophosphate
UMP uridine monophosphate

16. Structure of Nucleic Acids
Polymers of four nucleotides
Linked by alternating sugar-phosphate bonds
RNA: ribose and A, G, C, U
DNA: deoxyribose and A,G,C,T
nucleotide nucleotide nucleotide nucleotide
base
base
base
base
sugar
sugar P
sugar P
sugar P P

17. Nucleic Acid Structure
3,5-phosphodiester bond 3 5

18. Base Pairing in DNA: The Watson–Crick Model
In 1953 Watson and Crick noted that DNA consists of two polynucleotide strands, running in opposite directions and coiled around each other in a double helix
Strands are held together by hydrogen bonds between specific pairs of bases
Adenine (A) and thymine (T) form strong hydrogen bonds to each other but not to C or G
Guanine (G) and cytosine (C) form strong hydrogen bonds to each other but not to A or T

19. DNA stands for deoxyribose nucleic acid2
DNA stands for deoxyribose nucleic acid
This chemical substance is present in the nucleus
of all cells in all living organisms
DNA controls all the chemical changes which
take place in cells
The kind of cell which is formed, (muscle, blood,
nerve etc) is controlled by DNA
The kind of organism which is produced (buttercup,
giraffe, herring, human etc) is controlled by DNA

20. 3 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 called deoxyribose
a phosphate group -PO4 and
an organic base

21. or adenine deoxyribose 6 Nucleotides PO4 Thymine (T) Cytosine (C)
It is the phosphate group which gives DNA its acidic properties
Guanine
(G)

22. Joined nucleotides 7 sugar-phosphate + bases backbone PO4
A molecule of DNA is formed by millions of nucleotides joined together in a long chain

23. 8 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 chemical
bonds between the bases

24. Hydrogen Bonds in DNA The G-C base pair involves three H-bonds
The A-T base pair involves two H-bonds

25. Complementary Base Pairs
Two H bonds for A-T
Three H bonds for G-C

26. Replication of DNA
Begins with a partial unwinding of the double helix, exposing the recognition site on the bases
Activated forms of the complementary nucleotides (A with T and G with C) associate two new strands begin to grow

27. The Replication Process
Addition takes place 5  3, catalyzed by DNA polymerase
Each nucleotide is joined as a 5-nucleoside triphosphate that adds a nucleotide to the free 3-hydroxyl group of the growing chain

28. Transcription of DNA
RNA contains ribose rather than deoxyribose and uracil rather than thymine
There are three major kinds of RNA - each of which serves a specific function
They are much smaller molecules than DNA and are usually single-stranded

29. Messenger RNA (mRNA) Its sequence is copied from genetic DNA
It travels to ribsosomes, small granular particles in the cytoplasm of a cell where protein synthesis takes place

30. Ribosomal RNA (rRNA) Ribosomes are a complex of proteins and rRNA
The synthesis of proteins from amino acids and ATP occurs in the ribosome
The rRNA provides both structure and catalysis

31. Transfer RNA (tRNA)
Transports amino acids to the ribosomes where they are joined together to make proteins
There is a specific tRNA for each amino acid
Recognition of the tRNA at the anti-codon communicates which amino acid is attached

32. The Structure of tRNA

33. Transcription Process
Several turns of the DNA double helix unwind, exposing the bases of the two strands
Ribonucleotides line up in the proper order by hydrogen bonding to their complementary bases on DNA
Bonds form in the 5  3 direction,

34. Transcription of RNA from DNA
Only one of the two DNA strands is transcribed into mRNA
The strand that contains the gene is the coding or sense strand
The strand that gets transcribed is the template or antisense strand
The RNA molecule produced during transcription is a copy of the coding strand (with U in place of T)

35. Mechanism of Transcription
DNA contains promoter sites that are 10 to 35 base pairs upstream from the beginning of the coding region and signal the beginning of a gene
There are other base sequences near the end of the gene that signal a stop
Genes are not necessarily continuous, beginning gene in a section of DNA (an exon) and then resume farther down the chain in another exon, with an intron between that is removed from the mRNA