1. Gene and Chromosomal Mutations

2. What is a mutation?
Mutations are changes made to an organism’s genetic material.
These changes may be due to errors in replication, errors during transcription , radiation, viruses and many other things.
Mutations can occur within a specific gene (small scale), as well as to the chromosome as a whole (large scale).

3. Are mutations always bad?
Favorable mutations present organisms with an advantage over others and ensure their survival. These mutations will accumulate in a population.
Less favorable mutations are removed from the gene pool through natural selection.
Organisms with these mutations will not survive.

4. Small Scale Mutations Large Scale Mutations

5. Small Scale Mutations: Gene Mutations
There are three main types of gene mutations:
Point Mutations
Deletions (Frame shift mutations)
Insertions (Frame shift mutations)

6. Point Mutations
Point mutations occur when a single nucleotide in a gene is exchanged for another nucleotide.
For example, an A could be exchanged for a T or a C could be exchanged for a G.
These mutations have an effect on protein synthesis. One DNA triplet is altered, therefore one mRNA codon is altered, therefore one amino acid is affected

7. Examples of Point Mutations
Sickle cell anemia
Lactose intolerance

8. Insertions
Insertions occur when one or more new nucleotides are inserted into the DNA sequence.
When this occurs, there is a shift in the reading sequence of DNA during protein synthesis and a completely different protein strand may be formed.

9. Deletions
Deletions are when one or more nucleotides are removed from the DNA sequence.
As with insertions, this causes a shift in the reading sequence of DNA and can produce a completely different protein strand than the original.
Deletions are irreversible mutations.

10. Video Animation
Frame Shift Mutations

11. Large Scale Mutations: Chromosomal Mutations
There are three major chromosomal mutations that can occur:
Duplications
Inversions
Deletions

12. Duplication
Duplication occurs when a segment of a chromosome is doubled.
The segment of DNA that is doubled may contain many genes.

13. Inversions
Inversions occur when a piece of DNA is removed from the chromosome, inverted, and then placed back into the chromosome.
When it is re-inserted,
the genes are in reverse
order.
There is no loss of genetic material, however gene interactions may be altered and phenotypes may change.

14. Deletions Deletions occur when a whole chunk
of the chromosome goes missing.
Breaks in chromosomes can be caused by radiation, heat, viruses, chemicals, and other environmental causes.
Consequences of these mutations will depend on what part of the chromosome has been deleted.

15. Deletions Examples of disorders caused by deletions:
Prader-Willi Syndrome
Deletion of the long arm on chromosome 15
Characterized by compulsive eating

16. Deletions Cri-du-chat syndrome
Deletion of the short arm of chromosome 5