1. From DNA to Protein
Chapter 8
Mr. Scott

2. DNA Griffith and transformation Griffith experiment Transformation
Mice injected with pneumonia
Transformation
The process by which one strain of bacteria is changed by a gene or genes from another strain of bacteria
In 1928, Griffith was actually looking for something else – looking for how bacteria make people sick.
He had two strains, both of which grew well in his lab, but only one caused the infection.
When he injected the mice with the smooth type, the mice developed the infection and died.
He then decided to heat the harmful strain and then inject it into the mice – the mice survived.
This suggested that what was killing the mice was not chemically a poison released by the bacteria.
He then mixed the heat treated virus with the harmless virus and injected the mice.
Amazingly, the injection killed the mice
Upon examination of the mice he found neither the heat treated virus nor the harmless virus, but the disease causing virus.
He then hypothesized that the heat killed bacteria must have transferred some information to the harmless bacteria

3. DNA
Avery and DNA
DNA or nucleic acid inside is the material that is transferred during transformation
In 1944, Avery decided to repeat Griffith’s experiment.
They were trying to figure out which molecule in the heat killed bacteria was most important in transformation.
The treated the heat killed bacteria with enzymes that destroyed proteins, lipids, carbohydrates, and other molecules including nucleic acids
Transformation still occurred.
They repeated the experiment except this time they used enzymes that would destroy DNA
This time transformation did not occur

4. DNA The Hershey-Chase experiment Bacteriophage Radioactive markers
Virus that infects bacteria
Radioactive markers
1952 – Hershey and Chase used viruses (smaller than a cell that can infect a human).
Bacteriophage means bacteria eater.
Composed of DNA and RNA and a protein coat
When it enters an area it attaches to a cell and injects its genetic information into the cell.
Hershey and Chase attached radioactive markers to the protein coat and the DNA inside (each different) with the purpose of identifying which was entering the cell and causing the infection – protein or DNA
Markers – 32P DNA, 35S – Protein

5. DNA The components and structure of DNA Chargaff’s Rules Base pairing
A pairs with T
G pairs with C
DNA is a long molecule made up of necleotides
Each nucleotide is made up of 3 basic components
A 5 carbon sugar
A phosphate group
A nitrogenous base
Two of the nitrogenous bases are purines – adenine and guanine
Two are pyrimidines – cytosine and thymine
Backbone of DNA is composed of sugar and phosphate groups with the nitrogenous base sticking out sideways
Initially, scientists thought DNA was just a string of nucleotides.
Chargaff uncovered the percentages of bases in DNA – he discovered that the amount of guanine was nearly equal to the amount of cytosineand the same for the other two.
This became Chargaff’s rules.
The base units are held together in the middle by hydrogen bonds

6. DNA

7. DNA X-Ray evidence The double helix Watson and Crick
Two strands wrapped around each other
Rosalind Franklin then used a technique called x-ray diffraction.
She was able to get an xray of the DNA molecule
Combined with Chargaff’s work and Franklins image, Watson and Crick were able to make what became known as the Double helix

8. Replication DNA and Chromosomes Prokaryote Eukaryote
One circular DNA molecule
Eukaryote
1000 times the DNA
Prokaryotes lack the nucleus to contain the DNA and the DNA is thus referred to as the cell’s chromosome.
Euk. Contain a nucleus for housing the DNA and the number of chromosomes varies widely from species to species.

9. Replication DNA length
Roughly 1000 times the length of the cell it is in.
E. coli (bacteria) can contain over 4 million base pairs
Think of bowl, now try to pack 300 meters of spaghetti into the bowl with a lid.

10. Replication Chromosome structure DNA can be 1 meter in length
Chromatin
DNA and protein
Histones
Proteins that DNA wraps around
Nucleosomes
DNA and histones
A human cell contains as many as 1000 times the number of base pairs as a bacteria
Nucleosome – has a beadlike appearance due to the DNA wrapped around the histones.
The nucleosome begins to coil to take up the distance of the DNA
Most of the time the fibers of the nucleosome are dispersed throughout the nucleus, but during mitosis they begin to bunch together.
This packing of the chromosomes during mitosis helps to keep the chromosomes separate
Nucleosomes ultimately seem to be able to pack large lengths of DNA into small spaces.

11. Replication DNA replication Copying genetic information
Complimentary bases
Replication fork
Site where the chromosome seperates, and replication occurs
Watson and Crick also discovered when they found the shape how DNA replication would take place.
Each half is complimentary to the other half, so a new half could be generated from each half and is complimentary
In prokaryotes, replication begins at a single point and proceeds in two directions until the entire chromosome is replicated
In eukaryotes, DNA replication begins at several hundred different points. Replication will continue until the entire chromosome is replicated.

12. Replication Duplicating DNA Copying DNA
This is called replication
Makes two new identical strands
Replication insures that each cell will have a complete set of chromosmes.
During replication, the DNA strand seperates into two strands and then produces two identical strands
Each strand serves as the template for the two copy.

13. Replication How replication occurs Enzymes unzip the DNA strand
DNA polymerase
Proofreads the new strands
The unzipping occurs between the hydrogen bonds between the base pairs
Replication involves a bunch of enzymes
Remember that enzymes are very specific in the substance where their activity takes place.
DNA polymerase joins the individual nucleotides and also proofreads the new strands.

14. RNA and Protein Synthesis
Structure of RNA
Long chain of nucleotides
Differences from DNA
Sugar is ribose
RNA is single-stranded
RNA contains uracil instead of thymine
Think of RNA as a disposable copy of a segment of DNA
In many cases, the RNA strand is a working copy of a single gene.

15. RNA and Protein Synthesis
Types of RNA
mRNA
Messenger RNA
Carry instructions for putting amino acids together to make proteins
rRNA
Ribosomal RNA
Ribosomes put amino acids together
Ribosomes are also made of RNA (60%) and protein (40%)
tRNA
Transfer RNA
Transports amino acids to the ribosome
RNA molecules serve many functions – but for the most part they serve one function and that is code for proteins.
It is in the ribosome that the amino acids are also made into proteins.

16. RNA and Protein Synthesis
Transcription
RNA polymerase
binds to DNA at a promoter site
separates the two strands
One of the DNA strands is used to make a copy or RNA strand
Transcription is the process of copying the nucleotide sequence of DNA into a complimentary strand of RNA
This requires RNA polymerase
A promoter is the site on the DNA where the RNA polymerase attaches.
Promote5rs have certain base sequences which are the signals in the DNA
There are similar signals DNA to cause the transcription to stop

17. RNA and Protein Synthesis
RNA editing
Introns
Parts of the DNA that are not used to make proteins
Exons
Parts of the DNA that are used to make proteins
Gene splicing
Removing introns from the sequence
When the copy of RNA is made, it contains both the introns and exons in its sequence.

18. RNA and Protein Synthesis
The genetic code
Polypeptide
Chains of amino acids
Codon
Three nucleotide bases that represent an amino acid
64 possible codons from four letters
Start codon
Stop codon
There are 20 different amino acids
The property of the proteins are determined by the order in which the amino acids are assembled
How can you possibly get 64 combinations?
Only one codon codes for methionine which is the start code

20. RNA and Protein Synthesis
Translation
Ribosome reads the instructions found on the mRNA for making polypeptide chains or proteins
4 step process
Can you find them?
Translation is the process of decoding the mRNA into a polypeptide chain
Step 1 – Transcribe the RNA from DNA and release it into the cytoplasm
Step 2 – mRNA in the cytoplasm attaches to the ribosome.
As the mRNA moves through the ribosome the proper amino acid is brought into the ribosome by the tRNA.
Each tRNA carries only one type of amino acid and three unpaired bases which are called the anticodon
The anticodon pairs with the codon of mRNA and the amino acid is released from the tRNA
In the ribosome, the amino acid is added to the growing chain.
Step 3 – The amino acids form peptide bonds and the ribosome releases the tRNA so another tRNA can move in with its amino acid.
Step 4 – This continues until a stop codon is made and the polypeptide is released.

22. RNA and Protein Synthesis
Roles of DNA and RNA
DNA is the master copy
RNA is the blueprint or copy of the master plan
Why do we need a blueprint?
The blueprint is the copy, not the original. If the original is destroyed, you have a problem.

23. RNA and Protein Synthesis
Genes and Proteins
Genes contain instructions for making proteins
Proteins can be enzymes which control chemical reactions
Determine hair color, height, blood type, etc…

24. Mutations
Kinds of mutations
Mutations
Changes in genetic material

25. Mutations Gene mutations Point mutations Frameshift mutations
Changes in one or some nucleotides
Substitution – not so serious
Insertion or Deletion
Frameshift mutations
Insertions or deletions which can be very serious
A substitution usually affects no more than one amino acid

26. Mutations Chromosomal mutations
Changes in the number or structure of chromosomes
Deletions – loss of all or part of a chromosome
Duplications – extra copies of parts of chromosomes
Translocations – part of a chromosome breaks off and attaches to another
Inversions – reverse the direction of all or part of a chromosome

28. Mutations Significance of mutations Most mutations are neutral
Means they have little to no effect
Mutations can cause disruptions
Disorders
Cancer
Mutations can cause successful variations
Polyploidy
An organism has extra sets of chromosomes
In polyploidy, you may have triploid or tetraploid organisms.
Polyploidy plants are usually larger and plants have been produced purposely to exhibit this condition.

29. Gene Regulations Prokaryote gene regulation Operon
A group of genes that operate together
Two regulatory parts
Promoter
Binds RNA polymerase
Operator
Repressors attach to the operator and block transcription
Presence of some substance causes the repressor to be to busy to lock the operator
Using E. coli as an example for gene regulation – contains 4288 proteins in this bacteria
Three of the genes work together – operon
In E. coli, these three specific genes we are talking about must work together for the bacteria to us lactose as a food.
Therefore, these three proteins are called the lac operon.
Lactose is made of two simple sugars – galactose and glucose.
If we were to grow the bacteria on a plate and it contained lactose in the medium, it would have to transcribe the genes and produce the proteins necessary to break apart lactose.
If glucose were the only food in the medium, it would not need to code for these proteins.
The bacteria almost seems to known when to turn on the lac operon – it is turned off by a repressor and turned on by the presence of lactose
On one side of the operon’s three genes are two regulatory regions – promoter and operator
The promoter is where RNA polymerase binds and transcription begins
The operator is a site where a repressor molecule may attach and in effect turn off the lac operon.

30. Gene Regulations

31. Gene Regulations Eukaryotic Gene Regulation
Genes are usually controlled individually
Enhancers
Draw many proteins that can bind to these enhancers
TATA box
TATATA
TATAAA
Operons are not usually found in eukaryotes.
They have regulatory sequences that are much more complex than those of the lac operon
TATA box is an example of an enhancer – it serves as a marking point for RNA polymerase to begin transcription
The process of gene regulation in eukaryotes needs to be more complex because eukaryotes are more complex.
Even though a skin cell contains all the genetic information needed for everything in the body, it only uses a portion of the code to perform its essential functions, just as a liver, spleen, kidney cell does the same.

32. Gene Regulations Development and differentiation Differentiation
Cells become specialized in structure and function
Hox genes
Control the differentiation of cells and tissues in the embryo