1. Mutations Introduction
GTCHS Biology
J.H. Howard

2. 1. Mutation Basics Mutations:
Genetic mutant: an individual whose DNA or chromosomes differ from previous generations
Genetic changes among organisms always originate as some type of genetic mutation….what does this mean??

3. Causes of Mutations 1. Spontaneous mutations: 2. Induced mutations:
Example: DNA fails to copy correctly
2. Induced mutations:
Example: Environmental influences like chemicals
Carcinogen:

4. 2. Base Pairing Rules – Review
DNA – DeoxyriboNucleic Acid
Adenine, Thymine
Guanine, Cytosine
RNA – Ribonucleic Acid
Adenine, Uracil
If a mutation occurs in a region of DNA that codes for a specific amino acid needed in gene expression, there could be problems in the organism

5. Mutation and Evolutionary Development
Mutations are the basis of genetic changes and they allow for ___________________________....these occur BECAUSE of mutations in an individual’s genes…
Some mutations can help…
Silent mutation
Deleterious mutation
Recessive mutation

6. Mutations: large versus small-scale ‘mistakes’
Point mutations:
Chromosome mutation:

7. Types of DNA Mutations Substitution (Point Mutation) Insertion
Deletion
Frameshift

8. Results of DNA Mutations
Missense mutation:
Nonsense mutation:
Missense: Alters a nucleotide sequence so that a different amino acid is produced
Nonsense: alters a stop codon so that translation ends prematurely

9. Substitution (Point Mutation) – Sickle Cell Anemia

10. Chromosomal Mutations
Most often brought about by:
Translocation:
Deletion:
Duplication:
Inversion:
Translocation: The joining of a fragmented chromosome to a non-homologous chromosome is a translocation. The piece of chromosome detaches from one chromosome and moves to a new position on another chromosome
Deletion: This mutation results from the breakage of a chromosome in which the genetic material becomes lost during cell division. The genetic material can break off from anywhere on the chromosome.
Duplication: Duplications are produced when extra copies of genes are generated on a chromosome.
Inversion: In an inversion, the broken chromosome segment is reversed and inserted back into the chromosome.

11. Translocation

12. Deletion

13. Duplication

14. Inversion

15. Chromosomal Mutations
Chromosome number changes:
Aneuploidy:
Triploidy:
Tetraploidy:
Aneuploidy: A chromosome mutation that causes individuals to have an abnormal number of chromosomes is termed
Triploidy: extremely rare condition in whith the fetus has an extra set of 23 chromosomes; infants with this condition; typically do not come to full term…infants are usually small and have many birth defects
Tetraploidy: Where an organism has four complete sets of chromosomes….so 92 chromosomes per cell…most pregnancies result in miscarriages or infant dies shortly after birth

16. Triploidy

17. Tetraploidy

18. Repairing Mutations
Many organisms have evolved the abilities to fix mistakes made during DNA replication – Proofreading mechanisms
1. Mismatch repair
2. Excision repair

19. Effects of Mutation 1. No change in phenotype
2. Small change in phenotype
3. Big change in phenotype

20. Effects of Mutations – Control Genes

21. Control Gene – Hox gene “Master switches:”
Hox genes are a series of closely related genes that control embryonic development in animals…they are the ‘master switches’ meaning that the proteins they code for actually coordinate the activity of OTHER genes

22. Tumor Suppressor Genes and Oncogenes
Driver mutation:
Tumor suppressor gene:
Oncogene:

23. Mutation and Evolution
Mutation is the driving force behind:
Important to understand that mutations are _________________ (or have been for most of the history of life on earth…)
Mutations that occur in _____________________ can be inherited from one generation to the next
Occasionally, a mutation will give some sort of benefit or advantage to the organism that carries it….

24. Mutation and Evolution
Mutations allow for: Adaptation Environmental Change Natural Selection Species changes More evolution…

25. Mutation and Evolution
Discussion: How do you think current climate change will impact polar bears?
What are the polar bear’s options?

26. Mutation and Evolution
Example: Moths in Industrial England
During the onset of the industrial age in England, entire cities were covered with smog, ash, and soot – all this caused trees and forests to blacken
19th century naturalists noticed that the moths started to change….
The darkening of their wings allowed them to blend in better to the grimy background of the trees and could more easily avoid predators….By the mid 19th century, the dark peppered moths made up 90% or more of populations in the local area….this is an example of an ADAPTATION

27. Mutation and Evolution