1. The Structure of DNA and RNA Replication, Transcription, Translation

2. DNA & RNA are polymers of nucleotides
There are three types of nucleic acids in nature.
Adenosine triphosphate (ATP)
Energy Storage
Deoxyribonucleic Acid (DNA)
Ribonucleic Acid (RNA)
DNA and RNA are involved with the genetic aspects of the cell
DNA and RNA are polymers of nucleotides

3. The Building Blocks of DNA
Nucleic Acids
The Building Blocks of DNA
Deoxiribonucleic Acid – this where genetic
information is stored
DNA is a kind of nucleic acid, a polymer built from monomers called nucleotides
Ribonucleic Acid (RNA) – another group of
nucleotides, plays a role
in protein synthesis.
Nucleotides – are the building blocks (monomer) of
nucleic acid polymer
Only 4 types of nucleotides make – up DNA

4. DNA - Nucleotides
Each DNA molecule has three parts:

5. DNA - Nucleotides
The chemical bonds occur at specific locations in order to produce a functional unit.
Be able to draw this!!!!
All bonds within the nucleotide involve sharing electrons and are therefore COVALENT BONDS! (test question)

6. DNA - Nucleotides Nitrogenous Base – 4 nucleotides found in DNA
differ only in their nitrogenous
bases
Pyrimidines: single ring structure
Thymine (T)
Cytosine (C)
Purines: double ring structure
Adenine (A)
Guanine (G)

7. DNA - Nucleotides
AT CG At Coral Gables

8. Monomers to Polymers
The pattern (Pentose (sugar) - Phosphate- Pentose (sugar) -Phosphate)
This is called – Pentose Phosphate Backbone
Nitrogenous bases (AG ; CT) line – up along this backbone
Nucleotides of a nucleic acid polymer can combine in many different sequences
Sequences are essentially unlimited

9. Monomers to Polymers

10. The Double Helix Double Helix – Model created by Watson and
Crick; in which two strands of
nucleotides wound about each
other
Sugar phosphate backbones on the outside; Nitrogenous base on the inside.
Electrical charges related to the molecules of the two strands cause the twisting action of the DNA model

11. The Double Helix

12. Complementary Base Pairs
Base Pairing Rules
A with T (2 hydrogen bonds)
C with G (3 hydrogen bonds)
AT CG (Coral Gables)
Bonded by weak Hydrogen Bonds

13. Antiparallel
The 2 single strands that make up the double-stranded molecule run in opposite directions to each other.

14. DNA Replication
DNA replication occurs before cell division This ensures that cells carry the same genetic information This is also the method for inheritance.

15. DNA Replication
When a cell divides; a complete set of genetic instructions are created for each cell
Genetic material uses the template principle to make more DNA
There are 2 types of molecules important for the process of DNA replication:
Enzymes: helicase and a group of enzymes called DNA polymerase
Free nucleotides found free floating in the nucleoplasm (A,T,C,G)

16. Called Daughter Strands
DNA Replication
During DNA copying:
Two strands of the double helix separate
Each strand acts like a picture negative
Nucleotides line up one at a time across the existing strand (as per base pairing rule)
Enzymes link the nucleotides together to form two new DNA strands
Called Daughter Strands

17. DNA Replication
Helicase – the enzyme that initiates the separation of DNA into 2 single strands by breaking the hydrogen bonds
Helicase begins at a point or at an end of DNA molecule, and moves on complementary base pair at a time
Unpaired nucleotides on each of these single strands can now be used to create 2 double stranded DNA molecules identical to the original

18. DNA Replication

19. DNA Replication
DNA Polymerases – Catalyze covalent bonds between nucleotides of the new DNA strand
This happens really fast and it is really accurate
An error occurs in only one of a billion nucleotides
As this happens on one side the other strand goes through the same process in the opposite direction
DNA replication is described as a semi-conservative process because half of the pre-existing DNA molecule is always conserved (saved).
DNA Polymerases

20. Protein Synthesis DNA controls the proteins produced in a cell.
Some proteins are enzymes
The production of enzymes can have a dramatic effect on the biochemistry of the cell
Protein synthesis involves 2 major reactions:
Transcription
Translation

21. Protein Synthesis
As we know a gene is a sequence of bases along DNA chain
A gene is like a sentence; it’s a section of DNA that codes for a polypeptides
Specific strings of nitrogenous bases make-up a gene

22. RNA (ribonucleic acids)
Any nucleic acid whose sugar is ribose rather than deoxyribose (DNA)
Another difference is that the Nitrogenous Base Thymine is replaced by Uracil (U)
Similar to thymine
Also Pair with Adenine
RNA forms single strands NOT a double helix (like DNA)
RNA can twist

23. Messenger RNA (mRNA) Transcription – The process of converting a DNA
sequence to a form a single
stranded mRNA molecule.
mRNA molecule leaves the nucleus and is involved with the making of protein

24. Messenger RNA (mRNA)
Remember the nucleoplasm contains free nucleotides for DNA replication and for creating RNA
Each of the RNA nucleotides contain the sugar ribose not deoxyribose
Also the nucleotide thymine is replaced by uracil

25. The Transcription Process
Messenger RNA (mRNA)
The Transcription Process
Begins with an area of DNA of one gene becoming unzipped
Like DNA replication but only the section of the gene get unzipped
Only one of the 2 strands of DNA will be used to create the mRNA molecule
Enzyme RNA polymerase catalyzes the reaction
As RNA polymerase moves along the DNA starnd is acting like a template
RNA nucleotides float into place using the RNA base pairing rules

26. The Transcription Process

27. The Transcription Process
Triplet – any set of 3 bases that determine the identity of one amino acid
The genetic code for an amino acid is written in a language of 3 bases
A set of 3 bases contains enough information to code for one of the 20 amino acids
When the triplet is found in a mRNA molecule its called a codon (codon triplet)

28. Translation
There are three different kinds of RNA molecules and all are transcribed from a gene
mRNA
Ribosomal RNA (rRNA) – each ribosome is composed of rRNA and ribosomal protein
Transfer RNA (tRNA) – each type of tRNA transfers one of the 20 amino acids to the ribosome

29. Translation
Genetic Translation – the synthesis of polypeptides on ribosomes
This is how the flow of information from gene to protein is based on
Several codons form a sentence – that translates into polypeptide

30. Translation Anticodon Located at one end of the folded tRNA molecule
It is a specific triplet of bases
Are complementary (or matched up with) a specific codon in mRNA
Recognition follows base pair rules (AU / CG)
At the other end is the site where a particular amino acid recognizes both tRNA and its amino acid partner and links both together.
Requires

31. Translation
Ribosomes bind to mRNA in the cytoplasm and move along the molecule in a 5’ – 3’ direction until it reaches a start codon (AUG)
Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing
Each tRNA molecule carries a specific amino acid (according to the genetic code)
Ribosomes catalyze the formation of peptide bonds between adjacent amino acids (condensation reactions)
The ribosome moves along the mRNA molecule synthesizing a polypeptide chain until it reaches a stop codon
At this point translation ceases and the polypeptide chain is released

32. Translation

33. Triplet Code There are specific codons to represent amino acid
Some amino acids are coded by more than one codon
But no codon represents more than one amino acid

34. Triplet Code

35. This coding is shared by ALL organisms (almost all)
Triplet Code
There is also a code for stop
These come at the end of a sequence
There are sequence that do not code form an amino acids
This coding is shared by ALL organisms (almost all)
Production of human insulin in bacteria is an example of the universality of the genetic code allowing gene transfer between species

36. Polymerase Chain Reaction (PCR)
PCR is a means by which DNA replication can be carried out artificially in a lab setting.
Developed in the 1970’s
Only replicate short segments
Used to study and analyze DNA
Used in crime scenes (forensic situations)

37. Thermus Aquaticus (Taq)
A bacteria enzyme that is used in PCR that is stable at high temperatures
Bacteria occurs in hot springs
In addition the bacteria’s polymerase is also resistant to high temperatures
Taq polymerase
The use of Taq polymerase has allowed scientist to produce multiple copies of DNA quickly using the PCR technique