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Mutations

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Mutations, types , causes
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Mutations

  1. 1. •Mutations
  2. 2. Definition • Mutation is basically alteration of one or more nucleotides in an organism extra chromosomal DNA, virus or any material related to gene. • Mutations occur due to mutagens.
  3. 3. Generally: • Permanent change. • Vary in size from genome to genome. • Alteration may be single or large fragment containing one or more than one gene mutation is cause of dissimilarities between individuals of same species and different . • It may lead to evolution.
  4. 4. History: • Mutations idea extends from Darwin to modern genetics. • Since than there have been a lot of changes in the definition of the term • Today Mutations are important in order to differentiate between the individuals.
  5. 5. History: • Prof Sir Mike Stratton : • He was the first one who gave remarks on the mutations that occur in embryo. • Mutations can help in better understanding of human development.
  6. 6. Causes • DNA fails to copy accurately: Most mutation is naturally occurring .when cell devide it makes makes copy of DNA Some time copy not perfect. Small difference from original DNA is mutation. • External influences can create mutations Mutation can cause by specific chemicals or radiations. These cause to break DNA. When cell repair the DNA then it might not be a perfect job.
  7. 7. Types There are two types of mutations: • Gene Mutation • Chromosomal Mutation
  8. 8. Gene Mutation • Point Mutation: INDELL. • Frameshift: Substitution.
  9. 9. Gene Mutation • Gene mutation is describe as any change in the nucleotides sequence. • This change occur in single nucleotide base or large segment. • Due to this genetic variations occur. • Some variations may help for better survive. • Different mutagens which produce mutation.
  10. 10. Types • There are basic types 1. Point mutation i.) Insertion ii.) Deletion
  11. 11. Point mutation • Simple type of gene mutation. • Single base pair altered. • Mostly occur during DNA replication. • Caused by mutagens.
  12. 12. Insertion • One or more nucleotide base pair are added into a sequence of DNA.
  13. 13. Deletion • In which segment of DNA is removed which consist of one or more nucleotide.
  14. 14. • Point mutation on basis of protein structure: 1. Silent Mutation. 2. Missense Mutation. 3. Nonsense Mutation.
  15. 15. Frameshift Mutation • Frameshift mutation- Adding or deleting nucleotides to a DNA sequence. • A frameshift mutation is much worse than a point mutation because it causes the entire DNA sequence to be shifted over. Example: DNA: ATTAAACCG ATAAACCG
  16. 16. Frameshift Mutations: • Insertion: Nucleotide added – Entire DNA sequence changed • Deletion: Nucleotide missing – Entire DNA sequence changed
  17. 17. Tay-Sachs Disease: The absence of a vital enzyme called Hexosamindase A (Hex-A) Hex- A Accumulation of GM2 in nerve cells of the brain Normally However, in Tay-Sachs, there is no Hex-A so this process does not occur
  18. 18. Gene Location • Chromosome 15 showing location of the syndrome
  19. 19. Cystic Fibrosis • Inherited monogenic disorder presenting as a multisystem disease. • Typically presents in childhood ▫ 7% of CF patients diagnosed as adults • Most common life limiting recessive trait among whites
  20. 20. Cystic Fibrosis • Prognosis improving ▫ 38% of CF patients are older than 18 ▫ 13% of CF patients are older than 30 • Median survival: ▫ Males: 32 years ▫ Females: 29 years
  21. 21. Genetics of CF • Autosomal recessive. • Gene located on chromosome 7.
  22. 22. Genetics of CF • Most common mutation occurs in 70% of CF chromosomes 3 base pair deletion leading to absence of phenylalanine at position 508 (DF508) of the CF transmembrane conductance regulator (CFTR) • DF508 mutation leads to improper processing and intracellular degradation of the CFTR protein
  23. 23. Chromosomal Mutation • Deletion • Duplication • Tranlocation • Inversion
  24. 24. Deletion • Deletion is the lost of the nucleotides from the chromosomes the loss could be in larger number or in smaller number. • Deletion is actually when a base is deleted from the sequence. • Chromosomal fragment are lost due to deletion of a base. • There is no specific location for deletion, it can happens anywhere or everywhere.
  25. 25. • Sometimes the one copy of gene is lost from the organism which have two copies before or sometimes both the copies from an organism lost.
  26. 26. Duplication • Duplication is opposite to deletion. • A part is copied or replicated. • A sequence is repeated or may be a single base or two bases are repeated or duplicated. • This type of chromosome have an extra information or repeated information.
  27. 27. Mechanism of Duplication • There are following five mechanism of duplication that are defined below Ectopic recombination: • Duplication due to unequal crossing over occurs during meiosis in misaligned homologous chromosomes. • It occurs due to the replication of two elements of chromosome.
  28. 28. Replication Slippage • It is actually a error in the DNA due to which short sequences are repeated in the chromosomes. • DNA polymerases starts copiyng the DNA during replication process. • It place the Strand in wrong location and accidently copy the strand again due to which the duplication occurs. • Replication slippage is actually the repetitive sequences
  29. 29. Retrotransposition • Retrotransposons are genetic elements that can amplify themselves in a genome. • These DNA sequences use a "copy-and-paste" mechanism, whereby they are first transcribed into RNA, then converted back into identical DNA sequences using reverse transcription, and these sequences are then inserted into the genome at target sites.
  30. 30. Polyploid • Poliploid cells and organisms are those containing more than two paired (homologous) sets of chromosomes. • Most species whose cells have nuclei (Eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent.
  31. 31. Aneuploidy • Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. • It does not include a difference of one or more complete sets of chromosome.
  32. 32. Inversions: • An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. • Breakage and rearrangement within a chromosome. • Inversions do not change the overall amount of the genetic material. • Show no particular abnormalities at the phenotypic level.
  33. 33. • Inversions usually do not cause any abnormalities. • In individuals which are heterozygous for an inversion, there is an increased production of abnormal chromatids. • This leads to lowered fertility due to production of unbalanced gametes
  34. 34. Types: There are two types of Inversion mutation in chromosomes: • Pericentric Inversions. • Paracentric Inversions.
  35. 35. Pericentric Inversions: • Pericentric inversions include the centromere and there is a break point in each arm. • Chromosome can be elongated or shorted after the inversions have taken place.
  36. 36. Paracentric Inversions: • Paracentric inversions do not include the centromere and both breaks occur in one arm of the chromosome. • A reversal of the normal order of genes in a chromosome segment involving only the part of a chromosome at one side of the centromere.
  37. 37. Detection: • Cytogenetic techniques may be able to detect inversions, or inversions may be inferred from genetic analysis. In most species small inversions go undetected.
  38. 38. Example: • The most common inversion seen in humans is on chromosome 9, at inv(9)(p12q13). • No harmful effects. • Suspicion it could lead to an increased risk for miscarriage or infertility for some affected individuals.
  39. 39. Translocation: • A chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. • Translocations can be balanced or unbalanced.
  40. 40. Types: • Balanced: in an even exchange of material with no genetic information extra or missing, and ideally full functionality • Unbalanced: Where the exchange of chromosome material is unequal resulting in extra or missing genes.
  41. 41. Diseases Caused: • Some human diseases caused by translocations are: • Cancer: Described mainly in leukemia. Translocations have also been described in solid malignancies such as Ewing's sarcoma. • Infertility: If parent is a carrier of balanced then chances of an offspring being infertile are increased. • Down syndrome: Caused by Translocation between chromosome 21 and chromosome 14
  42. 42. Harmful Mutation • In which organism fitness is decreased and produced a diseases. • Sickle cell anemia, color blindness etc Are all mutations harmful? • Change the codes for protein synthesis. • Single mutation or more than 10 mutation.
  43. 43. Harmful Mutation Neutral Mutation: • Also called silent point mutation. • Eye color. Germ-Line Mutation: • Inherited. • Wilms Tumor.
  44. 44. Harmful Mutation Explanation: • Most inherited genetic diseases are recessive. • Some disease caused by one copy of defective gene. • Rare (Huntington’s Disease) • 5-10 deadly mutation in our body
  45. 45. Harmful Mutation Causes: i. Radiation (UV Radiation, X-rays) ii. Chemicals Also called mutagens. (Benzoyl peroxide, cigarette smoke) iii. Infectious Agents. (Human papillomavirus)
  46. 46. Harmful Mutation Chemicals Contaminations: • 28 April, 1986 • Chernobyl Disaster • 985,000 excess cancers occurred between 1986 and 2004. (Russian Publication) • 1.4 million excess cancers occurred (2001, European Committee on Radiation Risk)
  47. 47. Examples Sickle cell Anemia: • Hemoglobin-Beta gene found on chromosome 11. • Sickle shaped red blood cells. • Type of point mutation. • Two copies of the mutated genes cause sickle cell anemia.
  48. 48. Examples Huntington’s disease: • Mutation in chromosome number 4.(HD gene) • Basal ganglia cells are destroyed. • 50% chance. • Symptoms appear between 30 to 50 ages.
  49. 49. Examples Cancer: • Mutation in p53, BRCA1, BRCA2 • BRCA1 = breast cancer 1 • BRCA2 = Breast cancer 2
  50. 50. Beneficial mutation Beneficial Mutation: • Which are helpful for humans. • EXAMPLES i. Apolipoprotein AL Milano ii. Increased bone density iii. Malaria resistance iv. Tetrachromatic vision
  51. 51. Beneficial mutation Apo lipoprotein: • All humans have a gene which are said to be apolipoprotein. • The function of this gene is to transport cholesterol via the process of bloodstream. • It is considered more beneficially due to the removal of cholestrol from arteries.
  52. 52. Beneficial mutation Increased bone density: • The gene which caused bone density in human being are said to be low lipoprotein related to protein 5 (LRP5).
  53. 53. Beneficial mutation Malaria Resistance: • These variations occur in humans due to the hemoglobin variation that make it like sickle shape • The missing of one copy of that gene in human causes 29% chances to get malaria. On the other hand people with two copies of this gene respond to 93% of that disease
  54. 54. Tetra chromatic vision: • Different genes present in humans shows different color vision of light. • The gene which has one kind of cone show blue color at chromosome at 7.
  55. 55. Beneficial mutation in organisms: 1. Nylonase: nylon bacteria • Nylonase are the most authentic example of beneficial mutation in bacteria. • Nylonase eat the short molecule of nylon 6.
  56. 56. Gene mutation: Almond Trees: • The species which have almond contain amygdalin. • Amygdalin is a chemical that convert the cyanide into human body.

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