Basic Genetics  INDIAN DENTAL ACADEMY  Leader in Continuing Dental Education     www.indiandentalacademy.com
IntroductionGenetics is the study of genes This talk is intended to be an introduction to the principles and language of h...
Scope of Genetics Barely   40 years ago Genetics was just a  fanciful branch of Medicine without much  clinical significa...
Scope of GeneticsFor a clinician, genetics plays role in,1) Analysis, prediction and prevention of   disease and the days ...
Chromosomal Basis of Basic Heredity Nuclear material – normally homogeneous During    cell   division-Loses   homogeneit...
Chromosomal Basis of Basic Heredity The  chromosomal constitution of a person is  known as Karyotype (Chr Nos and  morpho...
Chromosomal Basis of Basic Heredity Genotype-    Genetic constitution of a person Phenotype -expression    of the genoty...
Chromosomal basis of basic heredity Human chromosomes     46 chromosomes of normal human somatic cells  constitute 23 hom...
Chromosomal Techniques Cellsfor chromosomal analysis must be capable of  growth and rapid division in culture So WBCs ar...
Chromosomal Techniques When    the cells are multiplying rapidly a dilute  solution of Colchicin is added which interfere...
Chromosomal Techniques The    cells are fixed on slides & stained by various  techniques. This    is now ready for micro...
A chromosome spread prepared from a lymphocyte culture. The same   cell is shown with solid staining (left) and giemso bon...
Chromosomal Techniques The   chromosome spread is photographed & chromosomes       are   cutout    from   the photograph ...
A human male Karyotype with Giemsa banding (G bonding). Thechromosomes are individually labeled and the seven groups A to ...
Denver classification Based  on overall length and centromere  position Depending on centromere Seven groups  from A to ...
Molecular structure &Function of chromosomes and            genes    Nucleus    Chromosomes    Segments of DNA with geneti...
DNA Two    polynucleotide chains, twisted to  form a double helix-Watson Crick  Double helix Rope ladder analogy Nucleo...
DNA   Each side is made up of    chains    of sugar  and    phosphate   The ‘step’ of the ladder is    made up of 2 nitr...
DNA The pairing always follows a fixed pattern,   1 purine pairs with 1 pyrimidine Adenine always pairs with Thymine -AT ...
DNA contd At nuclear division the two strands separate &  then each build its complement. So the genetic  information is ...
RNA DNA is mainly found in the chromosomes. RNA   is found mainly in the nucleolus and cytoplasm. RNA   has same struct...
Genes & Genetic information All   genetic material (DNA) contained in a  single cell is known as human genome It contain...
Genes & Genetic information Only 5% of DNA forms coding area. The   coding area of human genome is called gene 95%   of...
Genes & Genetic informationGenetic information is stored in DNA by meansof a code.A Code is a triplet of three adjacent ba...
Genes & Genetic           information At  5` end are promoter regions like ‘TATA  BOX’, ‘CCAT BOX’, Enhancer These     a...
How genes work? One   strand of gene forms a template for the synthesis of a RNA known as messenger RNA (mRNA)-Transcript...
How genes work? At3` end sequence AATTAA-gives signal for polyadenylation of RNA (poly`A` tail), after which it exits fro...
How genes work? Specific amino acids , delivered by tRNA, is added till the stop codon is reached, forming the desired pe...
Transcription & translation   www.indiandentalacademy.com
Formation of mRNATranscription and processing of a globin gene to form               mature messenger RNA        www.india...
Classification of genetic disorders1) Single gene disorder: By mutant gene.   Mutation in only one or both chromosomes,   ...
Symbols commonly used in pedigree chart      www.indiandentalacademy.com
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Patterns of single gene inheritance    Single gene traits depend on 2 factors    1)Whether gene responsible is an     aut...
Patterns of Single Gene      Inheritance       AUTOSOMAL Dominant         Recessive    X-LINKED( SEX LINKED) Dominant     ...
Patterns of Single Gene              Inheritance The   person who first brings a family to the  attention of the investig...
Patterns of Single Gene             Inheritance Allele   that is expressed whether hetero or  homozygous is DOMINANT All...
Patterns of Single Gene              InheritanceAutosomal dominant inheritance- Manifests in heterozygotes- Person possess...
Autosomal dominant and recessive      www.indiandentalacademy.com
Patterns of Single Gene                 Inheritance    Autosomal dominant inheritance(contd )-    Trait transmitted from o...
Patterns of Single Gene            InheritanceAutosomal dominant inheritance(contd ) Some      autosomal dominant traits ...
Autosomal dominant disorders Achondroplasia         Neurofibromatosis Huntington`s chorea    Tuberous sclerosis Marfa...
Patterns of Single Gene               InheritanceAutosomal recessive inheritance- Trait only in sibs (brothers & sisters) ...
Patterns of Single Gene             InheritanceAutosomal recessive inheritance- Heterozygotes with only one affected gene ...
Autosomal recessive disorderes  Congenital adrenal hyperplasia  Cystic fibrosis  Galactesemia  Sickle cell disease  P...
Sex linked inheritance Due to the situation on either X or Y chromosomes(sex chromosomes) Genes   on X chr are X-linked ...
Patterns of Single Gene InheritanceX-linked recessive trait    Ex: Hemophilia-   X-linked recessive trait is expressed by ...
www.indiandentalacademy.com
Patterns of Single Gene InheritanceX-linked recessive trait- Expression in female theoretically possible if  they are homo...
www.indiandentalacademy.com
X-Linked recessive Hemophilia A & B        Lesch-Nyhan Duschenne muscular       syndrome  dystrophy               Ocul...
Patterns of Single Gene            InheritanceX-linked dominant- Manifest in both in males who carry mutant  gene on X chr...
CHROMOSOMAL DISORDERS Lejeune   in 1959 demonstrated that children with Down`s syndrome had 47 chromosomes When to suspe...
CHROMOSOMAL DISORDERS When to suspect a chromosomal disorder?....contd  3)  Odd facies  4)  Abnormal ears  5)  Heart and ...
CHROMOSOMAL DISORDERS Chromosomal abnormalities can be    1) Numerical    2) Structural    NUMERICAL ABNORMALITIES:-   A ...
CHROMOSOMAL DISORDERS NUMERICAL ABNORMALITIES        contd - Monosomy is lack of a chromosome - Trisomy is due to non- di...
Disjunctionwww.indiandentalacademy.com
CHROMOSOMAL DISORDERS- Commonest type of aneuploidy is Trisomy-3  homologous instead of the normal pair- Lack of a chromos...
CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIESNOMENCLATURE:- Short arm of a chromosome-p- Long arm-q- Any addition or loss ...
CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-cond-These abnormalities result from chromosomebreaks and rearrangements-All...
CHROMOSOMAL DISORDERS- STRUCTURAL ABNORMALITIES-cond- The breakage may be :    1.Stable: Capable of passing through cell  ...
CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-cond- Deletion: Loss of a portion of chromosome- Deleted portion if it lacks...
CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-condDuplication :Presence of extra segment of chromosome-Morecommon, less ha...
CHROMOSOMAL DISORDERSInversion contd;If single arm is involved-paracentricIf involves centromere-pericentricInversion  ...
Structural disorderswww.indiandentalacademy.com
CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-cond Translocation: Exchange of segments between two non-homologous chromoso...
CHROMOSOMAL DISORDERSIsochromosomes:  During cell division the centromere of a chromosome sometimes mistakenly divides so ...
Translocation and isochromosome         www.indiandentalacademy.com
CHROMOSOMAL DISORDERSMosaicism:  If non-disjunction occurs at an early cleavage division(mitotic division) of the zygote r...
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Transcription and processing of a β globin gene       to form mature messenger RNA.         www.indiandentalacademy.com
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A diagrammatic representation of ultrastructure of a chromosome and the relationship between     DNA, histones and the chr...
Classification of chromosomes based on the positionof the centromere, and how they appear at anaphase                stage...
The structure of nucleosomes: DNA is wound round a     histone octamer to produce a nucleosome.           www.indiandental...
James D.Watson, F.H.C. Crick and M.F.H. Wilkins:           Nobel Laureates of 1962.         www.indiandentalacademy.com
Formation of nucleotide and the formation of a polynucleotide www.indiandentalacademy.com           strand.
Semiconservative method     The process of DNA replication. Both parental of DNA replication: One                         ...
The process of RNA synthesis or transcription,wher RNA is synthesized on one of the strands ofDNA. There are different sit...
The mRNA Codons Adenine (A):Guanine (G): Cytosine (C ) : www.indiandentalacademy.com          Uracil (U)
The code-codon-polypeptide relationship in      transcription and translation.      www.indiandentalacademy.com
Genetic engineering or            Bio-engineering It is modification of genetic structure of an  organism at the molecula...
Recombinant DNA technology It consists of* Inserting, foreign DNA, carrying genes for   valuable enzymes, hormones or othe...
Applications of genetic engineered                  bacteria1)    Human insulin2)    Human growth hormone3)    Gene therap...
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Basic genetics /certified fixed orthodontic courses by Indian dental academy

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Basic genetics /certified fixed orthodontic courses by Indian dental academy

  1. 1. Basic Genetics INDIAN DENTAL ACADEMY Leader in Continuing Dental Education www.indiandentalacademy.com
  2. 2. IntroductionGenetics is the study of genes This talk is intended to be an introduction to the principles and language of human genetics. It was Gregor Mendel, the Austrian monk who introduced us to the concept of heredity in 1860s www.indiandentalacademy.com
  3. 3. Scope of Genetics Barely 40 years ago Genetics was just a fanciful branch of Medicine without much clinical significance(of pure academic interest) Today genetics occupies a very important place in medicine www.indiandentalacademy.com
  4. 4. Scope of GeneticsFor a clinician, genetics plays role in,1) Analysis, prediction and prevention of disease and the days are not far off when it will play a very important role in treating the diseases. Already we are using many genetically engineered products like insulin and vaccines.2) Today genetics occupies the most important role in the diagnosis of diseases. Ex, presence of even a small sequence of DNA is enough to diagnose a disease( by PCR) www.indiandentalacademy.com
  5. 5. Chromosomal Basis of Basic Heredity Nuclear material – normally homogeneous During cell division-Loses homogeneity. Number of rod shaped organelle called chromosomes appear. Chromosomes contain DNA, in which units of genetic information or genes are present www.indiandentalacademy.com
  6. 6. Chromosomal Basis of Basic Heredity The chromosomal constitution of a person is known as Karyotype (Chr Nos and morphology) The genes are arranged along the chromosomes in linear pattern. Each gene has a precise position or locus Allele- alternative forms of a gene that can occupy the same locus www.indiandentalacademy.com
  7. 7. Chromosomal Basis of Basic Heredity Genotype- Genetic constitution of a person Phenotype -expression of the genotype as morphological, biochemical and physiological trait. Genome: Full DNA content of a chromosome set www.indiandentalacademy.com
  8. 8. Chromosomal basis of basic heredity Human chromosomes 46 chromosomes of normal human somatic cells constitute 23 homologous pairs (same gene loci in the same sequence), one from the father and one from the mother 22 pairs are alike in males and females-autosomes The remaining pair , the sex chromosomes differ in males and females, males-XY & females XX www.indiandentalacademy.com
  9. 9. Chromosomal Techniques Cellsfor chromosomal analysis must be capable of growth and rapid division in culture So WBCs are used ( RBCs are non nucleated) Heparinised blood is centrifuged to separate WBCS Cells are collected & placed in suitable tissue culture medium stimulated to divide by a mitogenic agent- phytohemagglutin Culture incubated for72 hrs www.indiandentalacademy.com
  10. 10. Chromosomal Techniques When the cells are multiplying rapidly a dilute solution of Colchicin is added which interferes with the action of the spindle by binding to tubulin of spindle microtubules and also prevents centromeres from dividing. Colchicin arrests mitosis at metaphaseA hypotonic solution is then added to swell the cells and separate chromatids known as Metaphase spread www.indiandentalacademy.com
  11. 11. Chromosomal Techniques The cells are fixed on slides & stained by various techniques. This is now ready for microscopic examination, photography and karyotyping WBCs are short lived. So for long-term culture studies, fibroblasts from dermis of the skin are used www.indiandentalacademy.com
  12. 12. A chromosome spread prepared from a lymphocyte culture. The same cell is shown with solid staining (left) and giemso bonding (right). www.indiandentalacademy.com
  13. 13. Chromosomal Techniques The chromosome spread is photographed & chromosomes are cutout from the photograph and arranged in pairs – This is karyotyping and the complete picture is the Karyotype www.indiandentalacademy.com
  14. 14. A human male Karyotype with Giemsa banding (G bonding). Thechromosomes are individually labeled and the seven groups A to G are indicated. www.indiandentalacademy.com
  15. 15. Denver classification Based on overall length and centromere position Depending on centromere Seven groups from A to G based on position, Metacentric- Cm central Submetacentric-Cm somewhat off centre Acrocentric- Cm near the end* Banding is done by staining www.indiandentalacademy.com
  16. 16. Molecular structure &Function of chromosomes and genes Nucleus Chromosomes Segments of DNA with genetic information www.indiandentalacademy.com
  17. 17. DNA Two polynucleotide chains, twisted to form a double helix-Watson Crick Double helix Rope ladder analogy Nucleotide is the unit of DNA composed of 1) Nitrogenous base 2) Sugar-Deoxyribose 3) Phosphate molecule www.indiandentalacademy.com
  18. 18. DNA Each side is made up of chains of sugar and phosphate The ‘step’ of the ladder is made up of 2 nitrogenous bases from 2 poles projecting inwards & the bases are joined by hydrogen bond. Nitrogenous bases are Purines-Adenine & Guanine Pyrimidines-Thymine & Cytosine www.indiandentalacademy.com
  19. 19. DNA The pairing always follows a fixed pattern, 1 purine pairs with 1 pyrimidine Adenine always pairs with Thymine -AT & Guanine with Cytosine-GC Each pair of complementary nitrogenous base is termed as a ‘ base pair’ ( bp) E.g. AT, CG, TA, GC • Length of DNA is expressed as base pairs. • 1000 bps =1 kilo base (kb) www.indiandentalacademy.com
  20. 20. DNA contd At nuclear division the two strands separate & then each build its complement. So the genetic information is conserved & transmitted to the daughter cell www.indiandentalacademy.com
  21. 21. RNA DNA is mainly found in the chromosomes. RNA is found mainly in the nucleolus and cytoplasm. RNA has same structure as DNA but in place of Thymine there is Uracil and the sugar is Ribose www.indiandentalacademy.com
  22. 22. Genes & Genetic information All genetic material (DNA) contained in a single cell is known as human genome It contains all the information of life Human genome contains about 3 billion base pairs(bp) www.indiandentalacademy.com
  23. 23. Genes & Genetic information Only 5% of DNA forms coding area. The coding area of human genome is called gene 95% of DNA contains stretches of non-coding areas referred to as ‘junk’ or ‘redundant’ or ‘selfish DNA’ www.indiandentalacademy.com
  24. 24. Genes & Genetic informationGenetic information is stored in DNA by meansof a code.A Code is a triplet of three adjacent bases.CODON is a coding for amino acidE.g.-UUU,AGA etcThere are 64 such possibilities www.indiandentalacademy.com
  25. 25. Genes & Genetic information At 5` end are promoter regions like ‘TATA BOX’, ‘CCAT BOX’, Enhancer These are important in transcription, controlling quantity of RNA & determining the site of transcription At 3` end the sequence AATTAA provides a signal for polyadenylation of RNA (poly ‘A’ tail) Poly A tail is essential for RNA to exit from the nucleus for translation www.indiandentalacademy.com
  26. 26. How genes work? One strand of gene forms a template for the synthesis of a RNA known as messenger RNA (mRNA)-Transcription In the nucleus the introns are excised & the exons are joined together & cap and tail are added to signify the start and end of code www.indiandentalacademy.com
  27. 27. How genes work? At3` end sequence AATTAA-gives signal for polyadenylation of RNA (poly`A` tail), after which it exits from nucleus, for translation( for protein synthesis) The mRNAin cytoplasm becomes a template in the ribosome for translation ThetRNA contains anticodons complementary to RNA codon for specific amino acid it carries. www.indiandentalacademy.com
  28. 28. How genes work? Specific amino acids , delivered by tRNA, is added till the stop codon is reached, forming the desired peptide, which is released from ribosome and used by the cell. www.indiandentalacademy.com
  29. 29. Transcription & translation www.indiandentalacademy.com
  30. 30. Formation of mRNATranscription and processing of a globin gene to form mature messenger RNA www.indiandentalacademy.com
  31. 31. Classification of genetic disorders1) Single gene disorder: By mutant gene. Mutation in only one or both chromosomes, 1: 2000 or less 2) Chromosomal disorders: Due to excess or deficiency of whole chromosome or chr. Segments. These can be i. Structural ii. Numerical 7:1000, ½ of all spontaneous Ist term abortions 3) Multifactorial:No characteristic pedigree pattern of single gene traits. May occur in families www.indiandentalacademy.com
  32. 32. Symbols commonly used in pedigree chart www.indiandentalacademy.com
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  34. 34. Patterns of single gene inheritance Single gene traits depend on 2 factors 1)Whether gene responsible is an autosome or a sex chromosome 2)Whether it is dominant, i.e.expressed even when present on only one chromosome of a pair, OR 3) Recessive- expressed only when present on both chromosome www.indiandentalacademy.com
  35. 35. Patterns of Single Gene Inheritance AUTOSOMAL Dominant Recessive X-LINKED( SEX LINKED) Dominant Recessive www.indiandentalacademy.com
  36. 36. Patterns of Single Gene Inheritance The person who first brings a family to the attention of the investigator is a Proband (Index case) Sibs or siblings- brothers or the sisters of the proband Alleles-Genes at the same locus on a pair of homologous chromosomes When a person has - A pair of identical alleles-Homozygous, - Different alleles-------------Heterozygous www.indiandentalacademy.com
  37. 37. Patterns of Single Gene Inheritance Allele that is expressed whether hetero or homozygous is DOMINANT Allele that is expressed only when homozygous is RECESSIVE www.indiandentalacademy.com
  38. 38. Patterns of Single Gene InheritanceAutosomal dominant inheritance- Manifests in heterozygotes- Person possesses both normal and mutant gene- Presence of any one mutant gene is enough for the disease- Homozygosity is rare-i.e..2 abn genes- Normal and abn genes are alleles www.indiandentalacademy.com
  39. 39. Autosomal dominant and recessive www.indiandentalacademy.com
  40. 40. Patterns of Single Gene Inheritance Autosomal dominant inheritance(contd )- Trait transmitted from one generation to the next i.e., trait in every generation - Both males and females are affected - Risk is 50% that is, affected person has 50% chance of transmitting. - Unaffected members do not transmit to children - Occurrence and transmission not affected by sex Ex: -Achondroplasia, Adult form of polycystic kidney www.indiandentalacademy.com
  41. 41. Patterns of Single Gene InheritanceAutosomal dominant inheritance(contd ) Some autosomal dominant traits are extremely variable in severity-the variability is referred to as expressivity. Ex- Osteogenisis imperfecta can vary from just blue sclera to full blown syndrome with deafness & multiple fractures.Penetrance: A person may carry a mutant gene & yet not exhibit any of its effects; the gene is then said to be non-penetrant. The degree of expression depends on penetrance www.indiandentalacademy.com
  42. 42. Autosomal dominant disorders Achondroplasia  Neurofibromatosis Huntington`s chorea  Tuberous sclerosis Marfan`s syndrome  Osteogenesis Acute intermittant imperfecta(some porphyria forms) Myotonic dystrophy  Fascio-scapulo- Adult polycystic humoral dystrophy  Familial kidney disease Noonan`s syndrome hypercholesterolemi a www.indiandentalacademy.com
  43. 43. Patterns of Single Gene InheritanceAutosomal recessive inheritance- Trait only in sibs (brothers & sisters) & not in their parents, offspring or other relatives- On an average ¼ th of the siblings of the proband are affected- Males & females are equally affected, but only in homozygotes-those with double dose of mutant gene.- Inbreeding increases the risk of this inheritance www.indiandentalacademy.com
  44. 44. Patterns of Single Gene InheritanceAutosomal recessive inheritance- Heterozygotes with only one affected gene are healthy- Offsprings of affected people are usually normal as it is less likely that an affected person marries another heterozygote for the same mutant gene- Generally affected individuals cannot be traced from one generation to next Ex; Cystic fibrosis www.indiandentalacademy.com
  45. 45. Autosomal recessive disorderes  Congenital adrenal hyperplasia  Cystic fibrosis  Galactesemia  Sickle cell disease  Phenyl ketonuria www.indiandentalacademy.com
  46. 46. Sex linked inheritance Due to the situation on either X or Y chromosomes(sex chromosomes) Genes on X chr are X-linked and Y are Y- linked There are no examples of Y-linked single gene disease. Sopractically all sex –linked disorders are X-linked www.indiandentalacademy.com
  47. 47. Patterns of Single Gene InheritanceX-linked recessive trait Ex: Hemophilia- X-linked recessive trait is expressed by all males who carry the gene- A mutant gene present on the single X is always manifest because it is unopposed by the modifying effect of a normal gene on the second X chromosome as happens in a female www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. Patterns of Single Gene InheritanceX-linked recessive trait- Expression in female theoretically possible if they are homozygous- Practically restricted to males- Heterozygous carrier is usually healthy- Affect males &transmitted by healthy female carriers- Never transmitted from father to son but his daughters will be carriers www.indiandentalacademy.com
  50. 50. www.indiandentalacademy.com
  51. 51. X-Linked recessive Hemophilia A & B  Lesch-Nyhan Duschenne muscular syndrome dystrophy  Ocular albinism Anhydrotic  Menke`s syndrome ectodermal dysplasia  Fabry`s disease Colour blindness Hunter`s syndrome G6PD deficiency www.indiandentalacademy.com
  52. 52. Patterns of Single Gene InheritanceX-linked dominant- Manifest in both in males who carry mutant gene on X chromosome and females who are heterozygous for the mutant gene- More common in females-twice- Affected male transmits the gene to all his daughters and none to his sons.- Affected female will transmit to half her offsprings of either sex. Ex: Vit D Res Rick www.indiandentalacademy.com
  53. 53. CHROMOSOMAL DISORDERS Lejeune in 1959 demonstrated that children with Down`s syndrome had 47 chromosomes When to suspect a chromosomal disorder? 1) Congenital malformations, esp. if more than one system is involved 2) Mental retardation of unknown origin www.indiandentalacademy.com
  54. 54. CHROMOSOMAL DISORDERS When to suspect a chromosomal disorder?....contd 3) Odd facies 4) Abnormal ears 5) Heart and kidney malformation 6) Abnormalities of hand and feet 7) Simian crease and single crease on the 5th finger 8) LBW1:150 newborn infants have chromosomal abnormalities www.indiandentalacademy.com
  55. 55. CHROMOSOMAL DISORDERS Chromosomal abnormalities can be 1) Numerical 2) Structural NUMERICAL ABNORMALITIES:- A cell withy exact multiples of haploid number(46,69,92) is known as euploid- Euploid with more than normal diploid numbers are polyploid- Other than euploid number-aneuploid- Ex of aneuploidy-trisomy 21, monosomy etc www.indiandentalacademy.com
  56. 56. CHROMOSOMAL DISORDERS NUMERICAL ABNORMALITIES contd - Monosomy is lack of a chromosome - Trisomy is due to non- disjunction of chromosomes in meiosis - Polyploidy is lethal in human beings i.e.. fertilization of one ova by two sperms www.indiandentalacademy.com
  57. 57. Disjunctionwww.indiandentalacademy.com
  58. 58. CHROMOSOMAL DISORDERS- Commonest type of aneuploidy is Trisomy-3 homologous instead of the normal pair- Lack of a chromosome –monosomy- During meiosis synapses occurs between each chromosome and its homologue. After separation each proceeds to an opp. Pole of the dividing cell. Failure of synapses or failure to separate (non-disjunction) may result in aneuploidy www.indiandentalacademy.com
  59. 59. CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIESNOMENCLATURE:- Short arm of a chromosome-p- Long arm-q- Any addition or loss of chromosomal material is denoted by + or – sign placed before the chromosome number, if a whole chromosome is involved Ex. +21- After a no. if any increase or decrease in length is involved Ex. Cri-du-chat(5p-) www.indiandentalacademy.com
  60. 60. CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-cond-These abnormalities result from chromosomebreaks and rearrangements-All structural abnormalities require at leasttwo chromosomal breaks followed by reunionof the broken ends www.indiandentalacademy.com
  61. 61. CHROMOSOMAL DISORDERS- STRUCTURAL ABNORMALITIES-cond- The breakage may be : 1.Stable: Capable of passing through cell divisions unaltered Ex:Deletions, duplications, inversions, translocations, insertions and isochromosomes 2.Unstable –Not capable of passing through the cell division unaltered. Ex. Dicentric, accentric rings www.indiandentalacademy.com
  62. 62. CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-cond- Deletion: Loss of a portion of chromosome- Deleted portion if it lacks centromere- acrocentric fraction. This fragment fails to move on the spindle in cell division due to the absence of centromere and is lost n subsequent cell divisions. This structurally abn chr lacks whatever genetic information was present in the lost segment. EX- Cri-du-chat syndrome in which part of the short arm of chromosome is deleted 46XXorXY, 5p- www.indiandentalacademy.com
  63. 63. CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-condDuplication :Presence of extra segment of chromosome-Morecommon, less harmfulInversion:Inversion involves fragmentation of achromosome by two breaks , followed byreconstruction with inversion of a section of thechromosomes between the breaks www.indiandentalacademy.com
  64. 64. CHROMOSOMAL DISORDERSInversion contd;If single arm is involved-paracentricIf involves centromere-pericentricInversion alone may not lead to an abn. phenotype, more true of paracentric as there is no change in arm ratio, whereas in pericentric there will/may be change of proportion of chromosomal arms www.indiandentalacademy.com
  65. 65. Structural disorderswww.indiandentalacademy.com
  66. 66. CHROMOSOMAL DISORDERSSTRUCTURAL ABNORMALITIES-cond Translocation: Exchange of segments between two non-homologous chromosomes-reciprocal or balanced translocation diagram www.indiandentalacademy.com
  67. 67. CHROMOSOMAL DISORDERSIsochromosomes: During cell division the centromere of a chromosome sometimes mistakenly divides so that it separates the two arms rather than the two chromatids diagram www.indiandentalacademy.com
  68. 68. Translocation and isochromosome www.indiandentalacademy.com
  69. 69. CHROMOSOMAL DISORDERSMosaicism: If non-disjunction occurs at an early cleavage division(mitotic division) of the zygote rather than during gametogenesis, an individual with 2 or more cell lines with different chromosome numbers, in the same individual is produced giving rise to a mosaic. www.indiandentalacademy.com
  70. 70. www.indiandentalacademy.com
  71. 71. www.indiandentalacademy.com
  72. 72. www.indiandentalacademy.com
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  88. 88. A diagrammatic representation of ultrastructure of a chromosome and the relationship between DNA, histones and the chromatin fibre. www.indiandentalacademy.com
  89. 89. Classification of chromosomes based on the positionof the centromere, and how they appear at anaphase stage of cell division. www.indiandentalacademy.com
  90. 90. The structure of nucleosomes: DNA is wound round a histone octamer to produce a nucleosome. www.indiandentalacademy.com
  91. 91. James D.Watson, F.H.C. Crick and M.F.H. Wilkins: Nobel Laureates of 1962. www.indiandentalacademy.com
  92. 92. Formation of nucleotide and the formation of a polynucleotide www.indiandentalacademy.com strand.
  93. 93. Semiconservative method The process of DNA replication. Both parental of DNA replication: One strands act as templates. While on the leading original strand is conserved and a new strand the replication is continuous, on the strand is synthesized. lagging strand it is synthesized in short pieces. www.indiandentalacademy.com
  94. 94. The process of RNA synthesis or transcription,wher RNA is synthesized on one of the strands ofDNA. There are different sites for synthesizing diferent types of RNAs. www.indiandentalacademy.com
  95. 95. The mRNA Codons Adenine (A):Guanine (G): Cytosine (C ) : www.indiandentalacademy.com Uracil (U)
  96. 96. The code-codon-polypeptide relationship in transcription and translation. www.indiandentalacademy.com
  97. 97. Genetic engineering or Bio-engineering It is modification of genetic structure of an organism at the molecular level to alter its characteristics The basic process of genetic engineering is called recombinant DNA technology www.indiandentalacademy.com
  98. 98. Recombinant DNA technology It consists of* Inserting, foreign DNA, carrying genes for valuable enzymes, hormones or other proteins, into DNA of some other organism so that it makes the desired product. *The essences of rDNA technology is process called gene cloning. *Cloning is a method of obtaining identical copies & cloning aims at obtaining identical copies of a desired gene www.indiandentalacademy.com
  99. 99. Applications of genetic engineered bacteria1) Human insulin2) Human growth hormone3) Gene therapy-Persons genes are altered to combat a disease by inserting gene into a cell or into a germ cell.-Somatic cell gene therapy is being tried in cystic fibrosis4) Genetic or DNA finger printing in dispute arising out of babies, parents etc5) Polymerase chain reaction www.indiandentalacademy.com

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