genetics in periodontal disease

2. Genetics is the science of heredity and variation in living
organisms.
Basic units of inheritance are called
GENES combination of DNA segments which together constitute an expressible unit
.
Modern genetics has expanded beyond inheritance to study the
functions and behaviour of genes.
Genetic epidemiology is the study of the role of genes and their
interaction with environmental factors in the occurrence of disease in human
populations .
The objectives of epidemiological studies in genetic science are to determine the
risks related to allelic variants of candidate genes, to map more accurately
regions of the genome for which there is evidence of linkage to disease
susceptibility, and to contribute cases to a genome wide search for susceptibility
genes .

3. Father of genetics-Gregor
Mendel

4. Autosome – chromosomes other than sex
chromosomes.
Autosomal dominant – the dominant effect of
one gene located on an autosome regardless of
the presence of the other, normal copy.
Autosomal recessive – A gene on an autosome
that is required in two copies to be active in an
individual. An individual who carries two such
copies of the same abnormal gene will be
subjected to effects from that gene.
TERMINOLOGY

5. Complementary DNA (cDNA) – the DNA sequence produced by the
enzyme called reverse transcriptase from messenger RNA. Very
frequently used in cloning experiments.
Chromosome – a nuclear structure carrying genetic information arranged
in a linear sequence. Humans have 23 pairs (including a pair of sex
chromosomes XX or XY).
Chromatin : Condensation of the DNA with histones and other
chromosomal proteins.Chromatin is further organized into chromosomes.
Cloning – the generation of sufficient copies of a target DNA sequence
that allows it to be sequenced or studied further.
Exon – the expressed portion of DNA or RNA that will ultimately be
translated into protein. Multiple exons are spliced together to remove
introns during RNA processing.

6. Gene expression – the process involving use of the information in a gene
via transcription and translation leading to production of a protein affecting
the phenotype of the organism determined by that gene.
Genetic code – in RNA and DNA, the consecutive nucleotide triplets (codon)
that specify the sequence of amino acids for protein synthesis (translation).
Genome – a term used to refer to all the genes carried by an individual or
cell.
Genotype – the genetic makeup of an organism or cell distinct from its
expressed features or phenotype.

7. Homozygous – the presence of identical alleles of one or more
specific genes (e.g. A/A).
Heterozygous – the presence of differing alleles of one or more
specific genes (e.g. A/B).
Intron – the intervening (non-coding) portion of DNA or RNA that is
removed during RNA processing.
Isoforms – a protein with equivalent function and similar or identical
sequence but derived from a different and usually tissue-specific
gene.
Linkage – the tendency for certain genes to be inherited together due
to their presence on the same chromosome.
.

8. Monozygotic twin – identical twins having identical sets of nuclear genes
as a result of separation of blastomeres.
Dizygotic twin – fraternal twins as a result of fertilization of two separate
eggs. They are no more similar genetically than are siblings.
Mutation – alteration of the genomic sequence compared to a reference
state. Not all mutations have harmful events (silent mutation).
Phenotype – the observable characteristics displayed by an organism as
influenced by environmental factors and independent of the genotype of
the organism.
Polymorphism – a region on the genome that varies between individual
members of a population present in a significant number of individuals.

9. Splicing – the removal of introns from transcribed RNAs. The removal of
exons results in the formation of ‘splice variants’ or ‘alternatively spliced’
protein isoforms allowing different proteins to be produced from the same
initial RNA or gene.
Alternative splicing – the generation of multiple protein isoforms from a
single gene via the splicing together of nonconsecutive exons during RNA
processing of some but not all of RNA transcripts. Believed to the
mechanism involved with the high number of proteins produced from a
smaller number of genes in humans.
X-linked disease – a disease of genetic origin as a result of a mutation on
the X-chromosome.
Diseases with etiologies that include both genetic and environmental
factors are refferred to as multifactorial.
Genetic marker refers to any gene or nucleotide sequence that can be
mapped to a specific location or region on a chromosome.

10. Trait and disease might be caused by a single gene (monogenic), several
genes (oligogenic), or many genes (polygenic).
In monogenic disorders, genes are referred to as causative because
almost everyone with the mutation develops the condition.
Environmental factors generally play a minor role in determining the
phenotype. In contrast, genes involved in complex multifactorial disease
are called susceptibility genes.

11. • A GENE is a hereditary unit that carries information for a
specific function and represents the position of DNA that
produces one RNA molecule.
• One strand of DNA contains many genes.
• Information carrier for polypeptide chain synthesis.
• GENES encode the Structural information for proteins and
instructions for their expressions.
• Proteins coordinate morphogenetic events and their
requirements are met by switching the genes that code for
specific proteins.
GENE

12. Every gene has three regions
EXON INTRON
PROMOTER CODING REGION TERMINATION SEQ
Promoter – turns the gene on and off.
Coding region – encodes the information to produce aminoacid
Termination sequence – signals the end of gene
Structure of gene

13. Chromosome
 Each Chromosome contains long
duplex of DNA.
 Building blocks of DNA are
nucleotides
-adenine(A),
-guanine(G),
-cytosine(C)
-thymine(T)
linked to deoxy ribose and PO4.
 Double helix of DNA in formed by
hydrogen bonding between
complimentary pairs(A-T& G-C)
23 pairs of
chromosomes
22 pairs of
autosomal
chromosome
1 pair of sex
chromosome

14. Chromosome
a. DNA + histone
protein:- nucleosome
c. Chromatin wound
into chromosomes
b. Nucleosomes wound into
chromatin

15. Locus
A locus is the specific location of a gene or a DNA
sequence on a chromosome.
eg: Gene at position “11q 23".
Chromosome 11
q- long arm
2- second region
3- 3rd band

16. Genome
 Genetic material of an
organism contained in
one haploid of
chromosomes
 Sum of ALL the genes
and intergenic
sequences of cell
 THE TOTAL
GENETIC
COMPONENT

20. DNA
RNA
Protein
Transcription
Translation
CENTRAL DOGMA

22. TRANSLATION

24.  In this analyses, the observed pattern of disease is
compared with those expected under various models of
inheritance to select the best fitting model.
 Low power to resolve heterogeneity( different causes
of disease)
 Cannot distinguish between genetic effects and
environmental causes.
This relationship
between nucleotide
sequence and amino
acid sequence is
known as the Genetic
code

26.  Start codon - AUG
 Stop codon - UAA, UAG, UGA

28. Allele
 A variant of the DNA or nucleotide sequence at a given locus
is called an allele. The genotype for each gene comprises the pair
of alleles present at that locus
Allele that leads to an observable phenotype –
dominant allele
Allele does not lead to an observable
phenotype- recessive allele.
Individual is considered homozygous
if the alleles are identical on homologous
chromosomes or heterozygous if the
alleles are different.

29. Mutation
 Mutation can cause variation in alleles.
 A mutation can be defined as a
structural change in genomic DNA which
can be transmitted from a cell to its
daughter cells.
 “Heritable change in a gene”

30. Gene mutations
 Point Mutation
 Missense Mutation
 Non Sense Mutation
 Silent Mutation

31.  Frameshift Mutation
Insertions
THE CAT SAW THE DOG
THE CMA TSA WTH EDO G
Deletions
THE CAT SAW THE DOG
THE AT S AWT HED OG

32. Polymorphism
 Allele is a variant form of a gene
 The coexistence of multiple alleles at a locus is
called “Genetic polymorphism” when they
occur at more than one percent in a population.

33. Where can polymorphisms
occur?
 Promoter region or 5’flanking region
 Exons or gene coding region
 Intergenic region or the introns
 The 3’ untranslated region.

34. Types of Polymorphism
 SNP: Single Nucleotide polymorphisms
 VNTR: Variable number of Tandem
Repeats.
 STR: Simple Tandem repeats.

35. 1.Single Nucleotide Polymorphism
-Variation in single base pair
- mutation rate of SNP is very low from generation
to generation
- Very numerous (every 0.3 – 1kb)
- Easily detectable with PCR
-1.42 million SNPs are present in human genome

36. 2.Minisatellite Polymorphism / Variable
Number Tandem Repeat(VNTR)

37. 3. Microsatellite Polymorphisms / Short
Tandem Repeat (STR)
- Short sequence of 1 – 4 bases
- Highly polymorphic
- more evenly distributed
- more numerous than mini satellite.

38. Influence of polymorphism on phenotype:
 Can be non functional
 Can be functional
• May change the amino acid
• thus can alter the protein
At Coding
region -
• Increase or decrease the
amount of protein.
At Promoter or
enhancer
region

39. Mutation Vs Polymorphism
Mutations Polymorphism
Frequency of less than 1% in
the population.
Follow Mendelian pattern of
inheritance.
Simple mendelian diseases
No redundancy.
Environmental influence is
minimal
Frequency of greater than 1% in
the population
Do not follow Mendelian pattern of
inheritance.
Complex diseases
Redundancy effect.
Significant environmental
influence.

40. The Genetic Etiology of Disease
Gene
Variant
Gene
Expression
Gene
Product
Altered
Physiology
Phenotype
(Disease)

42. POLYMORPHISMS IN CYTOKINE
GENES
CYTOKINE GENES AND PERIODONTITIS SUSCEPTIBILITY
IL-1, IL-18 TNF ALPHA
IL-6 IL-23
IL-4 IL-12
IL-10 IL-8
IL-17 IL-2

43. IL-1 GENOTYPE
 IL-1b
 IL-1a
 IL-RN
 IL-1b & IL-6 polymorphisms- recurent aphthous
stomatitis
 Red & orange complex organisms is increased in
genotype +ve pt = decreased IgG Ab response
Papapanou PN,. J Clin Periodontol 2001

44. IL -2 POLYMORPHISM:
A polymorphism in the position 330 (T-G)
of the IL-2 gene promoter cause an
imbalance in the immune response that is
mounted by the host.
IL- 4 POLYMORPHISM:
The polymorphism in the IL-4 gene cause
a skewing in the Th1/Th2 cytokine profile.
The absence of a balance between
proinflammatory & antiinflammatory
cytokines result in periodontal disease.
Scarel et al

45. IL- 10 POLYMORPHISM:
The 1087 SNP is a G to A substitution and
lies with a trancription factor binding site. The
1087 G allele is associated with high IL-10
production (Gonzales et al)
TNF POLYMORPHISMS:
Polymorphisms in TNF genes at positions
-238(Gto A) and -308(G to A). The 308 A allele
is associated with high promoter activity and
enhanced TNF production (Engebretson et al)

46. HEREDITARY GINGIVAL
FIBROMATOSIS
 Mutation in the SOS (Son of sevenless-1) gene.
 The insertion mutation(cytosine) introduces a
frameshift creating a truncated protein that abolishes
a vital portion of the protein .
 The resultant protein chimera has enhanced activity,
since it lacks the carboxyl terminal domain.
Garcia et al 1998

47. MMP POLYMORPHISM
MMP 3 gene polymorphism due to 1612
5A/6A substitution is significantly greater in
periodontitis than healthy. (Nagasee et al)
MMP 9 polymorphism is a result of C/T
substitution at 1562 promoter region is
associated with periodontal disease.

48. Ig Fc receptor
polymorphism
 Types - FcrRI, RII, RIII
 Low affinity receptors
 FcrRIIa
 FcrRIIb poor phagocytosis
 FcrRIIIa polymorphism
 FcrRIIIb

49. HLA GENETICS
 MHC class I molecules:
 HLA-A, HLA-B, HLA-C
 MHC class II molecules:
 HLA-DP,DQ,DR
 HLADRB1 1501- DQB10602 genotype has an
accelerated T cell response to p.gingivalis &
increased susceptibility to AP .
Takashiba S, J Periodontal Res 1999

50. FMLP RECEPTOR
POLYMORPHISMS
 The n-formyl-l-methionyl-l-leucyl-l-
phenylalanine (fMLP) peptides are thought to be
structural analogs of bacterial products involved
in chemotaxis of neutrophils to areas of bacterial
infection.
 Single nucleotide polymorphisms in the
fMLP receptor due to alterations in amino acid
changes involved in ligand binding and signal
transduction chemotactic response AP

51. PROTEASE GENES AND PERIODONTITIS SUSCEPTIBILITY
Genes coding for:
MMP-1 MMP-2
MMP-3 MMP-8
MMP-9 CATHEPSIN C
LACTOFERRIN MMP-13
MMP-12 TIMP-1,2, PAI-1
NEUTROPHIL ELASTASE
Polymorphisms in the Protease genes

52. POLYMORPHISMS GENES
IL-A(-889) and IL-B(+3954) IL-1 gene
TNF-α-308 allele 1 TNF α gene
TNF-β, ET-1 gene, ACE gene (deletion
/insertion polymorphism
TNF β, ET -1 and ACE gene
FcγRIIIb allotype Fc receptor polymorphisms
Chronic periodontitis:

53. POLYMORPHISMS GENE DISEASE
ASSOCIATION
ILA (-889),
IL-1B(+3954)
IL-1 Gene EOP
IL-4 Promoter &
Intron
polymorphisms
IL-4 Gene EOP
FcγRIII b allotype Fc receptor gene
polymorphism
EOP/GEOP
Gc locus chromosome 4q unknown EOP/LJP
VDR gene Vitamin D receptor
polymorphism
EOP/LJP
Aggressive periodontitis:

54. Segregation
analysis
Linkage
studies
Familial
aggregation
Candidate
gene
apprach
Genome
wide
analysis
Twin studies
Methods of Genetic analysis

55. • PSTGenetic Susceptibility Test is the first and only
genetic test that analyzes two interleukin 1 (IL1)
genes.
• Individuals with a positive PST genotype are
approximately 3 times more likely to lose teeth than
individuals who are genotype negative.
PERIODONTAL SUSCEPTIBILITY TEST

57. CONCLUSION
Periodontal disease is a consequence of the
complex interactions between host factors, genetics,
and the environment. Thus, interpretation of
genotype status must not be used solely to alter
treatment regimens and maintenance schedules.
Treatment outcomes will still be heavily influenced
by environmental and behavioral factors whether an
individual is genetically susceptible to disease or
not.

58. REFERENCES
 Gene polymorphisms in periodontal health and
disease. Periodontology 2000, Vol 40,2006, 94-106.
 Proceedings of the 2008 workshop on
inflammation: Journal of Periodontology:
Supplement: Vol:79; No 8: August 2008.
 The genetic basis of periodontitis. Kinane DF, Hart
TC. Periodontology 2000, 2005; Vol 39: 91-117.
 Genetic susceptibility to periodontitis:
Periodontology 2000, February 2012
 Gene polymorphisms and periodontitis:
Periodontology 2000, June 2011

59.  The role of genetic polymorphisms in periodontitis:
Periodontology 2000, Feb 2007.
 Genetic variants in periodontal health & disease.
Alexandrina Dumitrescu &Kobayashi J.
 Epigenetics and its role in periodontal diseases: a state-
of-the-art review. Larsson L, Castilho RM, Giannobile
WV.J Periodontol. 2015 Apr;86(4):556-68.
 Mini but mighty: microRNAs in the pathobiology of
periodontal disease. Kebschull M, Papapanou PN.
Periodontol 2000. 2015 Oct;69(1):201-20.

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