1. Mutations

2. What is a mutation?
A mutation is a permanent change in the genetic material (DNA) of an organism
Can involve an entire chromosome or a single segment of DNA.
There are mutations in two types of cells:
Sex cells (or germ-line cells)
Body cells (or somatic cells)

3. Sex-Cell Mutation Body-Cell Mutation
Mutations of the sex cells or germ-line cells do not affect the organism itself, but can be passed onto offspring
Body-Cell Mutation
Mutations of body cells or somatic cells in the body.
Affect the organism, but are not passed onto offspring
Example: Skin cancer

4. Types of Mutations
There are chromosomal mutations, which affect the chromosomes
There are point mutations that affect only a single nucleotide

5. Chromosome Mutation
Either a change in the structure of a chromosome or the loss of an entire chromosome
Always affects the genes
Types of chromosomal mutations:
Translocation
Deletion
Inversion
Duplication

7. Deletion
When the end of the chromosome breaks off or two simultaneous breaks lead to the removal of a segment
Example: Cri du Chat syndrome is when part of chromosome 5 is missing.
Results in a small head, delayed development, and intellectual disabilities. The infants cry sounds like a cat

8. Duplication
The presence of extra copies of genes in the same chromosome
This occurs when a segment of DNA attaches to its homologous chromosome or is made by unequal crossing over
Ex: Huntington’s Disease

9. Inversion
Occurs when a segment of genetic material is broken away from the chromosome and is re-inserted in reverse back into the chromosome.
It leads to the rearrangement of the gene sequence

10. Translocation
The movement of a chromosome segment to another location or different chromosome
Example: Translocation between chromosome 14 and 21 can lead to Down syndrome

11. Aneuploidy
When chromosomes fail to separate during meiosis, it causes problems such as nondisjunction

12. Point Mutation
Substitution, addition, or removal of a single nucleotide
Types of point mutations:
Substitution
Addition (insertion)
Deletion
They are chemical changes in just one base pair

13. Substitution
When one nucleotide is exchanged for another. The wrong nucleotide is placed.
Does not always affect the gene
If substitution results in the same amino acid, then the gene is not affected
If substitution results in a different amino acid, then the gene changes

14. Substitution Example of substituting a nucleotide:
Original codon: AUGGCCTGCAAA
Substituted codon: AUGGCCGGCAAA
Affected
Makes a different amino acid
Substituted codon: AUGGCTTGCAAA
Not affected
Makes the same amino acid

15. Addition (Insertion) An additional nucleotide is incorrectly added
Example of adding a nucleotide:
Original DNA: CGAATACAG
Amino Acids: Ala-Tyr-Val
New DNA: CCGAATACAG
Amino Acids: Gly-Leu-Cys

16. Deletion A nucleotide is left out Example of removing a nucleotide:
Original DNA: CGAATACAG
Amino Acids: Ala-Tyr-Val
New DNA: C_AATACAG
Amino Acids: Val-Met-?

17. Silent Mutation
A mutation is silent when the base substitution does not result in a change of the amino acid
There can be mutations in noncoding DNA or they can be in the coding portion of DNA, but not have any affect on the protein function
It is silent because of this

18. Missense Mutation This is also called a substitution
An amino acid is changed when one nucleotide is replaced by another, so a different protein is produced

19. Frameshift Mutation
One or two base pairs are inserted or deleted, causing a change in the reading frame. This results in a completely different protein.