1. Types of Mutations

3. Chromosome Mutations May Involve:
Changing the structure of a chromosome
The loss or gain of part of a chromosome
Ultimately they change either a gene or gene dosage

4. Chromosome Mutations Five types exist: Deletion Inversion
Translocation
Nondisjunction
Duplication

5. Deletion
Due to breakage
A piece of a chromosome is lost

6. Angelman Syndrome Caused by small deletion on Ch 15 inherited from mom
Paternal genes are normally suppressed
Developmental delay
Happy and excitable
Hand flapping

7. Inversion Chromosome segment breaks off Segment flips around backwards
Segment reattaches

8. Consequences of Inversions
Usually do not lead to abnormalities
Lead to decreased fertility

9. Duplication
Occurs when a gene sequence is repeated

10. Charcot-Marie-Tooth Syndrome
Chr 17 duplication
Inherited
Weakness of foot and lower leg muscles
High arches, hammertoes, and other deformities

11. Translocation Involves two chromosomes that aren’t homologous
Part of one chromosome is transferred to another chromosomes

12. Philadelphia Translocation
Individuals develop leukemia
Part of 8 and 22 go to Ch 9.
Fusion event leads to misexpression of one gene
Not inherited!
Philadelphia Chromosome

13. Translocation

14. Nondisjunction Failure of chromosomes to separate during meiosis
Causes gamete to have too many or too few chromosomes

16. Symptoms of Klinefelter Syndrome (XXY)
breast enlargement
lack of facial and body hair
likelihood to be overweight and taller than average males
Infertile (no sperm)

17. Chromosome Mutation Animation

18. Gene Mutations Change in the nucleotide sequence of a gene
May only involve a single nucleotide
May be due to copying errors, chemicals, viruses, etc. 18

19. Point Mutation Change of a single nucleotide
Includes the deletion, insertion, or substitution of ONE nucleotide in a gene 19

20. Point Mutation
Sickle Cell disease is the result of one nucleotide substitution
Occurs in the hemoglobin gene 20

21. Sickle Cell Disease Results from a Base Change in Beta Globin Gene
Figure 12.1

22. Frameshift Mutation Inserting or deleting one or more nucleotides
Changes the “reading frame” like changing a sentence
Proteins built incorrectly 22

23. Frameshift Mutation Original: The fat cat ate the wee rat.
Frame Shift (“a” added):
The fat caa tet hew eer at. 23

24. Amino Acid Sequence Changed24

25. Gene Mutation Animation25

26. Pedigree Analysis
figure out the genetic basis of a disease or trait from its inheritance pattern
predict the risk of disease in future offspring in a family (genetic counseling)

27. Basic patterns of inheritance
autosomal, recessive
autosomal, dominant
X-linked, recessive
X-linked, dominant (very rare)

28. Autosomal recessive traits
Trait is rare in pedigree
Trait often skips generations (hidden in heterozygous carriers)
Trait affects males and females equally

29. Autosomal Recessive mutations

30. Autosomal Dominant Trait is common in the pedigree
Trait is found in every generation
Affected individuals transmit the trait to ~1/2 of their children (regardless of sex)

31. Autosomal Dominant

32. X-linked recessive Trait is rare in pedigree Trait skips generations
Affected fathers DO NOT pass to their sons,
Males are more often affected than females

33. X-linked recessive

34. Pedigree Analysis in real life
Remember:
dominant traits may be rare in population
recessive traits may be common in population
alleles may come into the pedigree from 2 sources
mutation happens
often traits are more complex
affected by environment & other genes