1. DNA Replication
How to make a functional protein
Transcription
Translation

2. DNA Replication Will occur during S phase of the cell cycle.
Needed for mitosis/meiosis/tissue repair
DNA can only be added by DNA Pol I in a 5’ to 3’ direction
Causes creation of unique situation in the replication fork

4. DNA Replication Main Players Helicase - untwists DNA
Primase - makes RNA primer
Primase is of key importance in DNA replication because no known DNA polymerases can initiate the synthesis of a DNA strand without initial RNA primers
DNA polymerase III - synthesizes new DNA strands 
DNA polymerase I - removes RNA primer
DNA ligase repairs Okazaki fragments (seals lagging strand holes) 
DNA Replication

5. Making a functional protein involves
two processes
Transcription
Translation

6. The genetic code: The Key To Life
DNA
RNA
Nature’s building blocks

7. Gene expression: The flow of genetic
information from DNA via RNA to protein

8. Transcription Process: Overview
RNA-like strand
RNA polymerase (RNAP)- enzyme which catalyzes
transcription
unwinding of DNA (transcription bubble) near gene
before transcription can begin
initiation
elongation
termination
Like Replication
3 stages:

9. RNA processing after transcription produces
a mature messenger RNA (mRNA)
5’ Capping
Addition of methylated cap at the 5’ end.
Added by a special capping enzyme,
Critical for efficient translation of mRNA.
Polyadenylation
Addition of poly-A tail to 3’ end
Thought to stabilize mRNA from degradation
Aids in efficiency of translation
RNA splicing – removal of intron sequences
Exons -- are the coding regions that are
used to make proteins amino acid
coding regions

10. Transcription as it happens

11. siRNA-short interfering RNA.
Small interfering RNA (siRNA) is a tool that is revolutionizing bioscience research.
Many diseases develop from the undesirable production of proteins. Sirna's technologies provide a way to halt this problem at the source. By utilizing the cellular mechanisms that already exist, there is the potential to create drugs that halt or even cure these diseases.

12. Translation Transfer RNAs (tRNAs)
The process by which the genetic information
carried by mRNA directs the synthesis of proteins
from amino acids
Process brought about by 2 important molecules:
tRNA
Ribosomes (rRNA)
Transfer RNAs (tRNAs)
Function:
adapter molecule - brings specific amino acid to ribosome:mRNA complex

13. So….3 nucleotides = 1 codon = 1 amino acid
Unit of information is CODON   =   triplets of nucleotides in mRNA that encode the information for a specific amino acid in a protein
So….3 nucleotides  =  1 codon   =  1 amino acid       
mRNA

14. The Steps of Translation
rRNA
Initiation
A mRNA molecule in the cytoplasm
binds to a small ribosomal subunit
It proceeds downstream (5' -> 3') until
it encounters the start codon AUG.
Here it is joined by the large subunit
and a special initiator tRNA.
In eukaryotes, initiator tRNA carries
methionine (Met).

15. The Steps of Translation
2. Elongation
A tRNA covalently bound to its amino acid is
able to base pair with the next codon on the
mRNA
The preceding amino acid (Met at the start of
translation) is covalently linked to the
incoming amino acid with a peptide bond
(shown in red).
The initiator tRNA is then released and the
ribosome moves one codon downstream.
This shifts the more recently-arrived tRNA,
with its attached peptide, allowing the addition
of a new tRNA and amino acid

16. The Steps of Translation
3. Termination
The end of translation occurs when
the ribosome reaches one or more
STOP codons (UAA, UAG, UGA).
There are no tRNA molecules with
anticodons for STOP codons.
This causes the release of the
polypeptide from the ribosome.
The ribosome splits into its subunits,
which can later be reassembled for
another round of protein synthesis.

17. More than one ribosome can translate mRNA
at one time, making it possible to produce
many polypeptides simultaneously from a single
mRNA .

18. Translation – as it happens

19. Levels of Structure in polypeptide chains (proteins)
Primary structure
The amino acid sequence of the polypeptide chain
Secondary structure
The pleated or helical structure brought about by the formation of bonds between amino acids
Tertiary structure
3 dimensional structure of a protein due to folding on itself
Quaternary structure
Structure formed by the interaction of two or more polypeptide chains in a protein

20. Proteins have multiple functions
Proteins are the most abundant type of molecules found in any cell
Structural – ex collagen (fibrous connective tissue)
Storage – ex ferritin (stores iron in the spleen)
Regulatory – ex insulin (regulates glucose)
Transport – ex Hemoglobin (transport of O2 in blood)
Protection – ex Antibodies (form complexes with foreign proteins)

21. Proteins have multiple functions
Enzymes are one of the most important groups of
proteins in the cell
Act as biochemical catalysts
The function of all proteins depends ultimately on
the amino acid sequence of the polypeptide
chain