Download Name of structure?

Structure and Function
of DNA
4
3
5
9
2
7
1
8
6
10
RNA, what’s different from DNA?
RNA has the base uracil (U)
(Instead of thymine (T) in DNA)
The RNA sugar has 2 OH groups vs 1 in DNA
(Ribose vs deoxyribose)
Names of structures?
2
1
4
3
5
Complementary = DNA: A-T, C-G; RNA: A-U, C-G
What are the structures?
And, which is which?
Name of structure?
What type of bond is this?
Complementary = DNA: A-T, C-G; RNA: A-U, C-G
Learning check
1. Along one strand of a DNA double helix is the
nucleotide sequence GGCATAGGT.
Want is the sequence for the other DNA strand?
___ ___ ___ ___ ___ ___ ___ ___ ___
2. A molecule of DNA contains 2 polymer strands called
_________ made by bonding many monomers called
____________ together. Each monomer contains 3
parts: __________, _________ and _________.
3. DNA and RNA are polymers of _______ monomers.
4. What type of bond joins the bases of complementary
DNA strands?
What is the flow of Genetic
Information?
From DNA
1
To RNA
To Protein
In 2 stages
2
DNA is transcribed
The result is mRNA
mRNA is then translated
The result is a sequence of
amino acids in a polypeptide
But, what is the correspondence…
Between nucleotides of an
RNA
And the amino acids of a
polypeptide
What are the 4 types of nucleotides?
DNA: ATCG
RNA: AUCG
How do we get to protein?
There are 20 amino acids in protein
Each designated by a single letter
How do the 4 nucleotides specify 20 amino acids?
Amino acids are identified by triplets of bases which
Specify all the amino acids
What are the triplets of bases called?
Cod
ons
The genetic code is
The relationship between
nucleotide sequence
And amino acid sequence
One DNA codon (3 nt) => one RNA codon (3 nt) => one amino acid
How is this read?
Learning check
1. How many nucleotides are necessary to code for a
polypeptide that is 100 amino acids long?
2. An organism’s genetic information is stored within the
sequence of ___________.
3. The genetic information is transcribed into a sequence
of ____________.
4. (the answer to #3) are then translated into a sequence
of ______________.
5. The nucleotide sequence of a DNA codon is GTA. The
mRNA complementary sequence codon is _____.
6. The above codon codes for the _________ amino acid.
Did you know that the genetic code is
shared by all organisms?
All 20 amino acids are common to all living systems
The code is the same in different species
After genes have been
transferred,
(one species to another)
They can be transcribed and
translated
What does this allow for?
Mixing genes from various species
Tobacco plant
expressing firefly gene
Overview:
What is the flow of genetic information?
DNA RNA Protein
In eukaryotic cells where does transcription
occur?
The nucleus
Where is mRNA synthesized?
The nucleus
Where does translation occur?
The cytoplasm
What happens to protein as it is made?
It coils
It folds
It forms a 3-D shape
And, several polypeptide chains bind together
What are each of these shapes called?
How do genes control structures and activities
of cells?
Via transcription & translation processes
Learning check
1. Information in a gene is a specific linear sequence of
____________ in DNA.
2. The gene serves as a template in ____________.
3. The gene produces a ___________ strand of mRNA.
4. mRNA specifies a linear sequence of ___________.
The Genetic Basis of Cancer
In recent years, scientists have learned
more about the genetics of cancer
What have they identified?
That cells escape from control mechanisms
This causes changes in some of the cells genes
Or changes in the way certain genes are expressed
Cancer causing genes
First discovered in a chicken virus
What is a (chicken) virus?
Molecules of DNA or RNA
Surrounded by protein
How do they work?
Become a permanent resident in host cells
And, insert their nucleic acid into DNA
Of host chromosomes
What happens when they insert into a host cell?
They make the host cell cancerous
Is there something unique about the virus
nucleic acids?
They contain a gene that causes cancer
Called an oncogene (tumor gene)
In many cases we all have some of these genes…
They are called ‘proto-oncogenes’
They are normal genes that can become oncogenes
They are found in many animals
They code for growth factors
What do these growth factors do??
They are proteins that stimulate cell division
Or, are others that affect the cell cycle
What happens when these proteins malfunction?
Uncontrolled cell growth - cancer
What causes the proto-oncogene to malfunction?
A mutation must occur
Several types of mutations can occur
A mutation within a gene
An error in DNA replication = many gene copies
The normal location of the gene is changed
Proto-oncogene
Gene mutation
oncogene
Hyperactive! Growth
stimulating protein
Multiple gene
copies
Gene location
moved
New promoter
Normal growth stimulating
protein, but in excess!
In all cases, normal gene expression is changed =>
cell division
Which cancer is one of the best understood?
Colon cancer
What is the progression of colon cancer?
Begins as an unusually frequent division of
normal-looking cells in the colon lining
Several (4 or more) mutations are needed
Activation of cellular oncogene
And inactivation of 2 tumor-suppressor genes
These mutations result in altered signal transduction pathways
Then see full-fledged cancer cells
Typical colon cancer progression - mutations
Count the mutations…
Normal
cell
Malignant
cell
What do the mutations lead to?
Increased cell division
And, structure of cell grossly altered
Typical colon cancer progression – oncogene & TSG
What are the
cellular
changes?
DNA
changes?
Increased
cell
division
Growth of
benign
tumor
Growth of
malignant
tumor
Oncogene
activated
Tumorsuppressor
gene
inactivated
2nd Tumorsuppressor
gene
inactivated
What are cancer causing agents called?
Carcinogens
What is the carcinogen for these cancers?
1
Tobacco
2
UV radiation
Microscopic changes that happen when a person smokes
Normal lung tissue
Abnormal lung tissue
• Ciliated columnar
epithelia
• H = cilia sweep mucus
• J = goblet cell produces
mucus
• L = basal layer of cells
• Columnar cells
becoming crowded out
• Displaced by basal cells
• Fewer cilia, reduced
capability
• Chemicals in tobacco
toxic to cilia, paralyzing
• Smokers cough
Exam 3
Next Tuesday, 11/20/07
The exam covers:
Chapter 8, Mitosis & Meiosis
Chapter 10 Structure / Function of DNA
Some cancer:
Pages 128-129 & 211-215