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Mutations

Mutations. A. What Are Mutations?. Changes in the nucleotide sequence of DNA May occur in somatic cells – (aka. Body cells) - aren’t passed to offspring May occur in gametes - (aka. eggs & sperm) can be passed to offspring. B. Are Mutations Helpful or Harmful?.

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Mutations

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  1. Mutations

  2. A. What Are Mutations? • Changes in the nucleotide sequence of DNA • May occur in somatic cells – (aka. Body cells) - aren’t passed to offspring • May occur in gametes- (aka. eggs & sperm) can be passed to offspring

  3. B. Are Mutations Helpful or Harmful? • Mutations happen regularly • Mostmutations are neutral and have no major impact • Chemicals & UV radiation cause mutations • Many mutations are repaired by enzymes

  4. Are Mutations Helpful or Harmful? • Some type of skin cancers and leukemia result from somatic mutations • Some mutations may improve an organism’s survival (beneficial); mutations influence evolution by natural selection

  5. C. Types of Mutations

  6. 1. 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.

  7. Types of Gene Mutations • Include: • Point Mutations • Substitutions • Insertions • Deletions • Frameshift

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

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

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

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

  12. Amino Acid Sequence Changed

  13. Cystic Fibrosis (CF) • Monogenic • Cause: deletion of only 3 bases on chromosome 7 • Fluid in lungs, potential respiratory failure • Common among Caucasians…1 in 20 are carriers • Both parents have to be carriers of the mutated gene.

  14. Gene Mutation Animation

  15. Chromosome Mutations • May Involve: • Changing the structureof a chromosome • The loss or gain of part of a CHROMOSOME, not a gene

  16. 2. Chromosome Mutations • Five types exist: • Deletion • Inversion • Translocation • Nondisjunction • Duplication

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

  18. Inversion • Chromosome segment breaks off • Segment flips around backwards • Segment reattaches

  19. Duplication • Occurs when a gene sequence is repeated

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

  21. Translocation

  22. Nondisjunction • Failure of chromosomes to separate during meiosis • Causes gamete to have too many or too few chromosomes • Disorders: • DownSyndrome – three 21st chromosomes • Turner Syndrome – single X chromosome • Klinefelter’s Syndrome – XXY chromosomes

  23. Chromosome Mutation Animation

  24. Types of Gene Mutations A B C D E A C D E A B B C D E A C B D E A B H I J F G C D E • Original • Deletion • Duplication • Inversion • Translocation

  25. Karyotype – Used to identify gender and chromosomal genetic disorders

  26. Normal Male 2n = 46

  27. Karyotype Song – To the tune of I wish I had an oscarmeyerwienner. • A karyotype is a picture of condensed chromosomes. • The homologs are paired up and there are 22 autosomes. • Add in a pair of sex chromosomes and take a careful look. • If there is one too many or one too short, a nondisjunction happened and a disorder took.

  28. Normal Female 2n = 46

  29. Down’s Syndromeor Trisomy 21

  30. Male, Trisomy 21 (Down’s) 2n = 47

  31. Symptoms of Down Syndrome • Upward slant to eyes. • Small ears that fold over at the top. • Small, flattened nose. • Small mouth, making tongue appear large. • Short neck. • Small hands with short fingers.

  32. Symptoms of Down Syndrome • Low muscle tone. • Single deep crease across center of palm. • Looseness of joints. • Small skin folds at the inner corners of the eyes. • Excessive space between first and second toe. • In addition, down syndrome always involves some degree of mental retardation, from mild to severe. In most cases, the mental retardation is mild to moderate.

  33. Klinefelter’s Syndrome 2n = 47

  34. Kleinfelter’s syndrome(or Klinefleter’s) • Disorder occurring due to nondisjunction of the X chromosome. • The Sperm containing both X and Y combines with an egg containing the X, results in a male child. • The egg may contribute the extra X chromosome.

  35. XXY • Males with some development of breast tissue normally seen in females. • Little body hair is present, and such person are typically tall, have small testes. • Infertility results from absent sperm. • Evidence of mental retardation may or may not be present.

  36. Klinefleter’s

  37. Turner’s Syndrome 2n = 45

  38. Turner’s • Turner syndrome is associated with underdeveloped ovaries, short stature, webbed, and is only in women. • Bull neck, and broad chest. Individuals are sterile, and lack expected secondary sexual characteristics. • Mental retardation typically not evident. • Chromosomal or monogenic?

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