1. MUTATIONS
Chapter 12: pages 345 – 349

2. Mutation Goals
Explain the difference between chromosomal and gene mutations 2

3. Mutations MUTATION: an inheritable change in genetic information.
Can be spontaneous or caused by x-rays, ultraviolet light, or radioactive substances.
Gene mutations:
any chemical change that affects the DNA molecule 3

4. Gene Mutations
Point Mutation – involves a single nucleotide; such as the substitution of one nucleotide for another.
Can change one amino acid for which the gene codes
Sickle Cell Anemia 4

5. Gene Mutations
Frameshift Mutations – when a nucleotide is inserted or deleted resulting in the grouping of nucleotides being shifted.
Can cause tremendous changes to a polypeptide chain.
Mutation Repair 5

6. Gene Mutations 6

7. Chromosomal Mutations
involve a change in the structure of a chromosome
normal chromosome
one segment
repeated
three repeats

8. Duplication
Gene sequence that is repeated several to hundreds of times
Duplications occur in normal chromosomes
May have adaptive advantage
Useful mutations may occur

9. Deletion Loss of some segment of a chromosome
Most are lethal or cause serious disorder

10. Deletion
Cru-Du-Chat
Cru-Da-Chat Cry

11. Inversion A linear stretch of DNA is reversed within the chromosome
segments
G, H, I become inverted

12. Translocation
A piece of one chromosome becomes attached to another nonhomologous chromosome
Philadelphia chromosome arose from a reciprocal translocation between chromosomes 9 and 22

13. Translocation one chromosome a nonhomologous chromosome
nonreciprocal translocation

14. Chromosomal Mutations14

15. Chromosomal Mutations
Non-disjunction
occurs when chromosomes fail to separate properly during meiosis.
missing chromosomes (Monosomy)
too many chromosomes (Polyploidy).
Usually fatal in animals and therefore humans, although some like trisomy 21, are not fatal, but result in serious abnormalities.
Can result in hardier varieties in plants. 15

16. alignments at metaphase II nondisjunction at anaphase I
gametes
anaphase II
alignments at metaphase II
nondisjunction at anaphase I
chromosome alignments at metaphase I

18. Autosomal Nondisjunction

19. Downs Syndrome

20. Patau Syndrome Trisomy 13
Serious eye, brain, circulatory defects as well as cleft palate
1:5000 live births

22. Edwards Syndrome Trisomy 18 Every organ is affected 1:10,000 births
Life expectancy few months (full trisomy 18)

24. Sex Nondisjunction

25. Sex Nondisjunction Turner Syndrome Inheritance of only one X (XO)
98% spontaneously aborted
Survivors are short, infertile females
No functional ovaries
Secondary sexual traits reduced
May be treated with hormones, surgery

27. Sex Nondisjunction

28. Sex Nondisjunction Klinefelter Syndrome XXY condition
Results mainly from nondisjunction in mother (67%)
Phenotype is tall males
Sterile or nearly so
Feminized traits (sparse facial hair, somewhat enlarged breasts)
Treated with testosterone injections

30. Sex Nondisjunction

31. Sex Nondisjunction XYY Condition Taller than average males
Most otherwise phenotypically normal
Some mentally impaired
Once thought to be predisposed to criminal behavior, but studies now discredit