Mutations for ap bio

Genetic mutations, chromosomal and point mutations

1. Mutations all AP Students need to know

2. Mutations caused by whole/part chromosomes

3. Chromosomal mutations In nondisjunction , pairs of homologous chromosomes do not separate normally during meiosis As a result, one gamete receives two of the same type of chromosome, and another gamete receives no copy

4. Having an abnormal number of chromosomes is a condition known as aneuploidy Having 3 copies of a particular chromosome is called a trisomy Having 1 copy of a particular chromosome is called a monosomy

5. Polyploidy is a condition in which an organism has more than two complete sets of chromosomes Recent research has shown that this Chilean rodent is a tetraploid Very rare among animals Common in plants, some fish, some amphibians

6. Polyploidy - having more than two complete chromosome sets The normal state is having 2 of each chromosome (homologous pairs) When organisms have 3 or 4 of each chromosome, that is called polyploidy Triploidy (3n), tetraloidy (4n), hexploid (6n), octapolid (8n) Very uncommon in animals Some fish and amphibians, mostly Quite common in plants

7. Down Syndrome Caused by a trisomy of chromosome 21 1/700 births in US The result of nondisjunction during meiosis I Risk increases with the age of the mother Mental retardation, increased risk of other diseases, shortened life span, underdeveloped and likely sterile

8. Trisomy 18 – Edward’s syndrome low birth weight, mental retardation, extra fingers and toes

9. Trisomy of sex chromosomes Klinefelter syndrome is the result of an extra chromosome in a male, producing XXY individuals Monosomy X , called Turner syndrome, produces X0 females, who are sterile; it is the only known viable monosomy in humans

10. Quick Think Gene dosage, the number of active copies of a gene, is important to proper development. Identify and describe two disorders that are the result of improper gene dosage

11. Alterations of Chromosome Structure Chromosomal mutations include Deletion Inversion Duplication Translocation Often occur during meiosis Chromosomes break & rejoin incorrectly

12. Deletion mutations A piece of chromosome is lost during meiosis Cri du chat is one condition that results - distinctive cry, severe retardation, shortened life span

13. Inversion Mutations A double break where the piece reattaches, but backwards Hemophilia is a inversion on the X chromosome

14. Duplication mutation A piece breaks off from one chromosome and reattaches to the sister chromatid Fragile X syndrome is caused by this, 2nd most common form of mental retardation after Downs syndrome

15. Translocation mutation A piece breaks off one chromosome and reattaches to a different chromosome Burkitt’s lymphoma is caused by this

16. Sex-linked mutations in humans

17. Colorblindness Colorblindness Recessive X chromosome Men are more likely to be colorblind than women…WHY

18. Hemophilia Recessive, X-linked Prolonged bleeding when injured Clots slow to form Caused by a mutation for a gene on the X chromosome that codes for a blood clotting protein Can be treated but not cured Bleeding (bruising) after an injection

19. Duchenne muscular dystrophy Recessive, X-linked 1 /3500 males in US Progressive weakening of muscles Loss of coordination Death by early 20s Mutation in the gene that codes for a muscle protein ( dystrophin )

20. Point Mutations Small changes in the DNA sequence

21. Point Mutations point mutation = a change in a single base pair in a gene They can have catastrophic consequences, or none at all 3 main types: Substitution Insertion Deletion

22. Substitution mutations A base pair is replaced with a different base pair

23. Substitution Think of it like a sentence: Normal sentence would read THE DOG BIT THE CAT A point mutation might make the sentence read: THE DOG BIT THE CA R This changes the meaning of the sentence, but not dramatically.

24. Example: sickle cell anemia

25. Advantages of sickle cell AA – no sickle cell, susceptible to the worst effects of malaria Aa – no sickle cell, but call pass recessive allele to offspring, some protection from malaria aa – sickle cell disease This is called The Heterozygote Advantage

26. Changing a single base may not cause any change at all: The changed base may still code for the same amino acid Proline is coded for by CCC, CCA, CCG, and CCU, This is called a silent mutation

27. Insertions & Deletions Insertion - add extra letters Deletions – delete letters called frameshift mutations The 3 letter reading frame is shifted

28. Frameshift Mutations Think of it as a sentence again: THE DOG BIT THE CAT Adding an extra letter makes it: TH H EDO GBI TTH ECA T It changes the entire sentence to nonsense. This kind of mutation has a more dramatic effect on the DNA sequence and is usually lethal

29. 1. 2. 3. What kind of mutation is represented by 1, 2, and 3? Will mutation 1 affect the resulting protein?

30. Tay -Sachs Frame shift mutation – 4 added nucleotides (insertion) Autosomal, recessive

31. Cystic Fibrosis Deletion frameshift mutation – 3 missing letters, autosomal recessive

32. Breast/Ovarian Cancer BRCA I and BRCA II – usually a deletion mutation Autosomal dominant

33. Huntington’s Disease Autosomal dominant >37 CAG repeats on the short arm of chromosome 4