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Chapter 14 Sec 1: Genes in Action

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1 Chapter 14 Sec 1: Genes in Action

2 Mutation: The Basis of Genetic Change
The change in the structure or amount of the genetic material of an organism

3 Mutant An individual whose DNA or chromosomes differ from a previous or normal state.

4 Evolution Genetic differences among organisms originate as some kind of genetic mutation

5 Causes of Mutation Occur naturally as accidental changes to DNA or to chromosomes during the cell cycle Mutagens: environmental factors like radiation & some chemicals

6 Effects of Mutation A small change in the DNA can affect one amino acid in a protein Only noticed if they cause a disease

7 Kinds of Mutations Different kinds of mutations are recognized as either changes in DNA or changes in the results of genes

8 Mutations as Changes in DNA

9 Point Mutation Change of a single nucleotide in a sequence from one kind of base to another

10 Insertion or Deletion Errors in replication can cause the deletion or insertion of a nucleotide

11 Mutations as Changes in Results of Genes

12 Silent Mutation It has no effect on a gene’s function Point mutation

13 Missense Mutation Results when a codon is changed such that the new codon codes for a different amino acid

14 Frameshift Mutation Causes the starting point of “reading” the gene to change which translates to different codons

15 Nonsense Mutation Results when a codon is changed to a STOP signal
Protein may fail to function

16 More or Fewer Amino Acids
If the insertion or deletion is a multiple of 3, reading will be preserved Protein will have fewer amino acids

17 Chromosomal Mutations

18 At a chromosome level In eukaryotic cells, the process of meiosis creates the chance of mutations at the chromosome level

19 Deletion Occurs when a piece of chromosome is lost

20 Duplication Occurs when a piece remains attached to its homologous chromosome after meiosis

21 Inversion Occurs when a piece reattaches to its original chromosome, but in a reverse direction

22 Translocation Occurs when a chromosome piece ends up in a completely different, nonhomologous chromosome

23 Gene Rearrangement Chromosomal mutation can move an entire gene to a new location Likely to disrupt the gene’s function

24 Effects of Genetic Change

25 Germ Cell Mutations in germ cells can be passed on to the next generation

26 Sickle Cell Anemia Recessive trait
Poor blood circulation, pain, organ damage

27 Tay-Sachs Disease Recessive trait
Deterioration of central nervous system Death in early childhood Caused by defective form of an enzyme

28 Cystic Fibrosis Recessive trait Mucus buildup in organs
Difficulty breathing and digesting

29 Hemophilia Recessive, sex linked
Failure of blood to clot, excessive bleeding and bruising

30 Romanoffs - Hemophilia

31 Pedigree for Hemophilia

32 Huntington Disease Dominant trait
Gradual deterioration of brain tissue in middle age Shorter life expectancy

33 Achondroplasia Homozygous Dominant – Don’t survive
Heterozygous Dominant – Lead normal lives and can reproduce

34 Camptodactyly Genetic abnormality that affects the shape and movement of fingers Variation in the phenotype of the trait

35 Examples:

36 Cri-du-chat Deletion from chromosome 5 resulting in mental retardation and the development of an abnormally shaped larynx

37 Progeria Syndrome A set of symptoms that characterize a disorder
Hutchinson-Gilford Progeria syndrome: mutated gene that leads to premature aging and reduced life expectancy

38 Progeria Syndrome Gene mutates at random
Dominant over its normal partner on the homologous chromosome

39 Progeria Syndrome

40 Large-scale genetic change
Can occur by misplacement, recombination, or multiplication of entire chromosomes

41 Nondisjunction When pairs of chromosomes fail to separate properly

42 Down Syndrome Extra chromosome 21 Mental retardation
Congenital heart defects Shorter limbs

43 Karyotype

44 Turner Syndrome (XO) Missing one X chromosome
Female in appearance but their sex organs do not develop at puberty and they are sterile Short stature, broad based neck

45 Turner Syndrome

46 Klinefelters Syndrome (XXY)
Male in appearance and sterile Taller than average Usually notice when males don’t develop at puberty

47 Karyotype

48 XYY Individuals are somewhat taller than average and often have below normal intelligence Used to think they were prone to violence

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