1. Mutations

2. Mutations
A mutations are a change in the sequence of bases in DNA or RNA
Mutations are essential for evolution to occur
Mutations are the ultimate source of all new
genetic material within a species
Most have no effect at all
Some are beneficial
Some are harmful

3. Causes Some happen spontaneously
Due to mistakes in DNA replication or in the
process of transcription
Others are caused by environmental factors
These factors are called mutagens
Germline mutations
Occur in gametes
Can be transmitted to offspring and will
be in every cell in the offspring

4. Causes Somatic mutations Occur in other cells of the body
Have little effect because these are
confined to one cell and its daughter cells
Can't be passed on to the offspring

5. Mutagens

6. Chromosomal Alterations
Changes in the structure of the chromosome(s)

7. Chromosomal Alterations
These tend to be very serious
Often result in the death of the organism in which they occur
If the organism survives it may be affected in multiple ways
Human example - Down Syndrome
A duplication mutation
3 #21 chromosomes

8. Point Mutations Type Description Example Effect Silent
Mutated codon codes for the same amino acid
CAA (Glutamine)
CAG Glutamine)
None
Missense
Mutated codon coes for a different amino acid
CCA (Proline)
Variable
Nonsense
Mutated codon is a premature stop codon
UAA (Stop)
Usually serious

9. Frameshift Mutations
A deletion or insertion of one or more nucleotides that changes the reading frame of the base sequence
Deletions take away nucleotides
Insertions add nucleotides
AUG-AAU-ACG-GUU = Start-Asp-Thre-Ala
AUG-AAA-UAC-GGU-U = Start - Lys-Tyr-Gly

10. Effects of Mutations May be positive, negative, or neutral
Cells also have repair mechanisms to fix errors
If the damage is permanent it can't be fixed
Beneficial Mutations
Essential for evolution to occur
Increase chances of surviving or reproducing
Antibiotic resistance in bacteria
Town in Italy
protects from atherosclerosis

11. Harmful Mutations Proteins that don't function properly
May cause genetic disorder or cancer
Genetic disorder
in one or a few genes
Cystic fibrosis
in a single gene
Cancer - uncontrolled cell growth
Some cancer genes can be inherited

12. Regulation of Gene Expression
Not all cells make or need the same proteins
Using a gene to make a protein is called gene expression
This needs to be regulated
When, Where and How much
We will look at regulation during transcription
Controlled by regulatory proteins
Bind to the DNA at places called regulatory
elements, which are near regions called
promoters

13. Regulation of Gene Expression
Regulatory proteins bind to these elements
Activators or Repressors
Interact with RNA polymerase which
transcribes DNA into mRNA
Activators promote transcription
Repressors prevent or inhibit transcription

14. Regulation of Initiation

15. Prokaryotic Gene Expression
It is much simpler
Regulation involves something called operons
A region of DNA that consists of one or more
genes that encode the proteins needed for
a specific function
The operator is the region of the operon
where regulatory proteins bind

16. Eukaryotic Gene Expression
Very complicated
Many regulatory proteins and regulatory elements involved
Involved enhancers
Regions of DNA that can loop back and
interact with a gene's promoter

17. The TATA Box
Some patterns of regulatory elements are present in all genes
The TATA box is part of the promoter of most eukaryotic genes
Regulatory proteins bind here
When they are done binding RNA
polymerase recognized the complex and
goes to work transcribing the gene

18. Regulation during Development
Regulation is very important when an organism is developing
Genes need to be turned on and off in just
the right sequence and time
Homeobox genes are examples of genes that
regulate development
The switch on whole series of major
developmental genes
In insects the hox genes insure that
body parts develop in the right place.

19. Homeobox Genes

20. Gene Expression and Cancer
Mutations that cause cancer generally occur in two types of regulatory genes
Tumor-suppressor genes
Proto-Oncogenes
These genes produce regulatory proteins
that control the cell cycle
When these genes mutate - cells with
mutations divide rapidly and without limits

21. How Cancer Develops Mutation inactivates Tumor suppressor
Cells proliferate
Mutation inactivates DNA repair gene
Mutation of proto-oncogene creates an oncogene
Mutation inactivates several more tumor suppressor genes
Cancer