This document provides an overview of the history and key developments in genetics and its relationship to orthodontics. It begins with Gregor Mendel's discoveries in 1866 laying the foundations of genetics. Major milestones include the discovery of DNA structure in the 1950s and determining the genetic code in 1966. Advances enabled genetic engineering, cloning, and the Human Genome Project. The document discusses cellular and molecular components involved in inheritance including DNA, genes, mutations. It examines genetic transmission patterns and disorders relevant to orthodontics like cleft lip/palate. Twin and pedigree studies are described as methods to study genetic influences on traits.

1. GENETICS IN ORTHODONTICS
PROF (Dr.) SAIBEL FARISHTA

2. FATHER OF
MODERN
GENETICS
1866
GREGOR MENDEL
PUBLISHED THE
RESULTS OF HIS
INVESTIGATIONS
OF THE
INHERITANCE OF
"FACTORS" IN PEA
PLANTS.

3. 1950's
ROSALIND FRANKLIN (1920-1957),
MAURICE WILKINS, FRANCIS H. C.
CRICK OF BRITAIN AND JAMES D.
WATSON OF THE U.S. DISCOVER
CHEMICAL STRUCTURE OF DNA,
STARTING A NEW BRANCH OF
SCIENCE - MOLECULAR BIOLOGY

4. WATSON AND CRICK
MADE A MODEL OF THE
DNA MOLECULE AND
PROVED THAT GENES
DETERMINE HEREDITY
1953

5. 1957
ARTHUR KORNBERG OF THE
U.S. PRODUCED DNA IN A
TEST TUBE.

6. 1963
F. SANGER OF BRITAIN
DEVELOPED SEQUENCING
PROCEDURE FOR PROTEINS.

7. 1966
THE GENETIC CODE
WAS DISCOVERED;
SCIENTISTS WERE
NOW ABLE TO
PREDICT
CHARACTERISTICS BY
STUDYING DNA. THIS
LEADS TO GENETIC
ENGINEERING,
GENETIC COUNSELING.

8. 1972
PAUL BERG OF THE U.S.
PRODUCED THE FIRST
RECOMBINANT DNA
MOLECULE.

9. 1983
BARBARA MCCLINTOCK
(1902-1992) OF THE U.S.
WAS AWARDED THE NOBEL
PRIZE FOR HER DISCOVERY
THAT GENES ARE ABLE TO
CHANGE POSITION ON
CHROMOSOMES.

10. THE LATE 1980'S
AN INTERNATIONAL
TEAM OF SCIENTISTS
BEGAN THE PROJECT
TO MAP THE HUMAN
GENOME.
THE FIRST CRIME
CONVICTION BASED
ON DNA
FINGERPRINTING, IN
PORTLAND OREGON.

11. 1990
GENE THERAPY WAS USED
ON PATIENTS FOR THE
FIRST TIME.

12. 1994
THE FDA APPROVED THE
FIRST GENETICALLY
ENGINEERED FOOD
‘FLAVRSAVR TOMATOES’
ENGINEERED FOR BETTER
FLAVOR AND SHELF LIFE

13. 1997
DOLLY THE SHEEP - THE
FIRST ADULT ANIMAL
CLONE.

14. 2000
J. CRAIG VENTOR, ALONG
WITH FRANCIS COLLINS,
JOINTLY ANNOUNCE THE
SEQUENCING OF THE
ENTIRE HUMAN GENOME.

15. MOLECULAR BASIS OF INHERITANCE
CELL
THE CELL IS THE BASIC UNIT OF ANY LIVING BODY. IT IS MADE UP OF
DIFFERENT ORGANELLES LIKE CELL WALL, CYTOPLASM, ENDOPLASMIC
RETICULUM, RIBOSOMES, MITOCHONDRIA, NUCLEUS, ETC.
THE CHROMOSOME
WITHIN THE NUCLEUS OF EACH CELL ARE THREAD LIKE STRUCTURES OF
DIFFERENT LENGTHS AND SHAPES CALLED CHROMOSOMES. THE NUMBER OF
CHROMOSOMES PRESENT IN EVERY CELL OF AN ORGANISM IS CONSTANT,
BUT IT CHANGES FROM ONE SPECIES TO ANOTHER.

16. CELL & NUCLEUS
A DIAGRAM OF A TYPICAL CELL
FROM THE HUMAN BODY. IN THIS
PICTURE WE GET A SENSE OF
WHERE THE DNA RESIDES IN THE
CELL AS WELL AS HOW IT IS
ORGANIZED IN THE NUCLEUS.
DOUBLE-STRANDED DNA IS
ORGANIZED INTO
CHROMOSOMES. CHROMOSOMES
ARE SITUATED IN THE NUCLEUS
AND THE MEMBRANE BOUND
NUCLEUS IS FOUND IN THE CELL.

17. DNA
CHROMOSOMES ARE MADE UP OF LONG CHAINS OF DEOXY-RIBONUCLEIC ACID (DNA)
MOLECULES, TWISTED AND TWINED IN A SPECIFIC MANNER. EACH LONG STRAND OF
A DNA MOLECULE IS A CHAIN OF NUCLEOTIDES.
THE BASIC NUCLEOTIDE UNIT COMPRISES OF A DEOXYRIBOSE SUGAR, A PHOSPHATE
MOLECULE AND ONE PROTEIN, EITHER PURINE OR PYRIMIDINE. THE NUCLEOTIDES
FORM A PAIR BY A WEAK HYDROGEN BOND BETWEEN THE PROTEINS. AT THE SAME
TIME, THE SUGAR MOLECULES ON BOTH SIDES GET ATTACHED TO AN ADJACENT PAIR
BY MEANS OF PHOSPHATE BONDS. THE STRUCTURE RESEMBLES A STEP LADDER

18. DNA STRUCTURE
A ROTATING, WIRE FRAME MODEL
OF A WATSON-CRICK DNA
DOUBLE HELIX. THE TWO CHAINS
RUN ANTI-PARALLEL TO EACH
OTHER AND CONTAIN MATCHED
PAIRS OF NITROGENOUS BASES:
ADENINE WITH THYMINE (A-T),
GUANINE WITH CYTOSINE (G-C).
THIS COMPLEMENTARY
STRUCTURE ALLOWS FOR TWO
IDENTICAL DAUGHTER
MOLECULES TO BE MADE FROM A
SINGLE PARENT MOLECULE AND
IS TERMED “SEMICONSERVATIVE”
REPLICATION, MEANING ONE
STRAND OF THE NEW DNA
MOLECULE COMES FROM THE
ORIGINAL DNA.

19. DNA REPLICATION
IN THIS ANIMATION, ADENINE, WHICH
IS GREEN, IS THE COMPLIMENTARY
BASE PAIR FOR THYMINE, WHICH IS
PINK. GUANINE, WHICH IS YELLOW
FORMS A COMPLEMENT WITH
CYTOSINE, WHICH IS BLUE. NOTE THE
SPECIFIC WAY IN WHICH THE
DIFFERENT NITROGENOUS BASES
ARE PAIRED. THE ADENINE-THYMINE
(A-T) PAIR IS FORMED BY TWO
HYDROGEN BONDS AND THE
GUANINE-CYTOSINE (G-C) BASE PAIR
HAS 3 HYDROGEN BONDS. ADENINE
CAN ONLY BOND WITH THYMINE AND
VICE-VERSA. IN THE SAME FASHION,
GUANINE AND CYTOSINE CAN ONLY
BOND WITH EACH OTHER. IN THIS
WAY, EACH STRAND IS THE
COMPLIMENT OF THE OTHER AND
ALLOWS FOR THE
SEMICONSERVATIVE OF DNA
REPLICATION.

20. THE COMPLEX STRUCTURE OF A CHROMOSOME CAN BE EXPLAINED BY ‘ THE
SOLENOID MODEL OF CHROMOSOMAL STRUCTURE’ (FINCH AND KLUNG).
THE GENE -
THE GENE FORMS THE BASIC UNIT OF INHERITANCE BY DETERMINING THE MAKE-UP
AND STRUCTURE OF A PARTICULAR CHARACTERISTIC IN AN ORGANISM. A GENE
CONSISTS OF A PORTION OF THE DOUBLE STRANDED DNA MOLECULE WITH 300-
1000 NUCLEOTIDE PAIRS. EACH CHROMOSOME CONSISTS OF HUNDREDS AND
THOUSANDS OF NUCLEOTIDE PAIRS, WHICH CAN BE CONSIDERED AS A SEQUENCE
OF GENES.
TRANSCRIPTION -
TRANSCRIPTION IS THE PROCESS BY WHICH INFORMATION IS TRANSMITTED FROM
DNA TO THE MESSENGER RNA AT THE INITIAL STAGE OF REPLICATION.
TRANSLATION -
TRANSCRIPTION IS THE PROCESS IN WHICH THE GENETIC INFORMATION IS
ACTUALLY CONVERTED INTO PROTEIN SYNTHESIS.

21. PATTERNS OF GENETIC TRANSMISSION
THE PATTERN OF GENETIC TRANSMISSION WITHIN THE DENTOFACIAL COMPLEX CAN
BE OF 3 TYPES -
REPETITIVE -
IT IS CHARACTERIZED BY RECURRENCE OF A DENTO FACIAL DEVIATION WITHIN THE
IMMEDIATE FAMILY AND IT’S PROGENITORS.
DISCONTINUOUS -
IT IS CHARACTERIZED BY RECURRENCE OF A MALOCCLUSION TRAIT THAT
REAPPEARS WITHIN THE FAMILY BACKGROUND OVER SEVERAL GENERATIONS, BUT
NOT CONTINUOUSLY.
VARIABLE -
IT IS CHARACTERIZED BY THE OCCURRENCE OF DIFFERENT BUT RELATED TYPES OF
MALOCCLUSION WITHIN SEVERAL GENERATIONS OF THE SAME FAMILY.

22. GENE MUTATIONS
PROTEIN SYNTHESIS FOR THE PROCESS OF REPLICATION IS CONTROLLED BY GENES.
A CHANGE PRODUCED BY CERTAIN AGENTS IN THE COMPOSITION OF THE BASE PAIR
OF THE DNA MOCECULE, MAY LEAD TO THE SYNTHESIS OF AN ALTERED PROTEIN.
THIS MAY RESULT IN AN ALTERED EXPRESSION OF CERTAIN SPECIFIC
CHARACTERISTICS OF THE INDIVIDUAL.
GENE MUTATIONS CAN BE OF VARIOUS TYPES LIKE – VISIBLE, DETRIMENTAL, LETHAL
MUTATIONS ETC.
MUTAGENS ARE AGENTS THAT INDUCE GENETIC MUTATIONS. THEY CAN BE DUE TO -
1. IONIZING RADIATION
2. CERTAIN DRUGS, CHEMICALS AND FOOD ADDITIVES
3. CERTAIN VIRUSES
4. HIGH TEMPERATURE
SOMETIMES, SPONTANEOUS GENE MUTATIONS MAY ALSO TAKE PLACE.

23. CHROMOSOMES IN MAN
IN 1956, TJIO AND LEVAN AND INDEPENDENTLY FORD AND HAMERTON
DEMONSTRATED THAT THE NUMBER OF CHROMOSOMES IN MAN IS 46, 23 PAIRS.
AMONG THESE, 44 (22 PAIRS) ARE AUTOSOMES AND A PAIR OF SEX CHROMOSOMES.
THE AUTOSOMES IN MALE AND FEMALE ARE IDENTICAL, BUT THE SEX
CHROMOSOMES ARE DIFFERENT. MALES, OUT OF 2 SEX CHROMOSOMES, HAVE ONE X
AND ONE Y CHROMOSOMES, WHILE FEMALES HAVE 2 X CHROMOSOMES.

24. NORMAL MALE
SHOWS 23 PAIRS OF CHROMOSOMES. TWENTY TWO PAIRS ARE CALLED
AUTOSOMES, 1 PAIR IS CALLED THE SEX CHROMOSOME; XY IN A MALE.
MALES ARE ASSOCIATED WITH SECONDARY SEXUAL CHARACTERISTICS LIKE
ABUNDANT FACIAL HAIR, VOICE, OTHERS. DIFFERENCES ARE ALSO EVIDENT
IN THE GENITALIA.

25. NORMAL FEMALE
SHOWS 23 PAIRS AS IN THE MALE, BUT SEX CHROMOSOMES ARE REPRESENTED BY
XX. FEMALES ALSO HAVE DIFFERENT PHYSICAL FEATURES FROM MALES. A BARR
BODY IS ALSO PRESENT IN CELLS OF THE FEMALE, REPRESENTING AN INACTIVATED
X CHROMOSOME.

26. GENETICS IN AN ORTHODONTIC PERSPECTIVE
IN 1836 F G KUSSEL REPORTED THAT MALOCCLUSION, BOTH SKELETAL AND DENTAL
CAN BE TRANSMITTED FROM ONE GENERATION TO ANOTHER.
DENTOFACIAL DISTURBANCES OF GENETIC ORIGIN CAN BE BRIEFLY BE LISTED AS -
1. MICROGNATHIA
2. MACROGNATHIA
3. CLEFT LIP AND PALATE
4. DOWN’S SYNDROME
5. GARDNER’S SYNDROME
6. MARFAN’S SYNDROME
7. CHERUBISM
8. CLEIDO CRANIAL DYSPLASIA
9. MANDIBULO FACIAL DYSOSTIS
10.OSTEOGENESIS IMPERFECTA
11.BIMAXILLARY PROTRUSION
12.BIMAXILLARY ATRESIA
13.RETARDED ERUPTION OF TEETH
14.HYPODONTIA, ANODONTIA, OLIGODONTIA, ETC
15.ABNORMAL NUMBER AND ARRANGEMENT OF TEETH
HUMAN RACIAL CROSSING PRESENT LITTLE OR NEGLIGIBLE RISK TO DENTAL
OCCLUSION.

27. KLINEFELTER'S SYNDROME
THREE SEX CHROMOSOMES ARE ASSOCIATED WITH KLIENFELTER RATHER THAN THE
EXPECTED 2 - XXY. THESE INDIVIDUALS ARE MALES WITH SOME DEVELOPMENT OF
BREAST TISSUE NORMALLY SEEN IN FEMALES. LITTLE BODY HAIR IS PRESENT, AND
SUCH PERSON ARE TYPICALLY TALL, WITH OR WITHOUT EVIDENCE OF MENTAL
RETARDATION. MALES WITH XXXY, XXXXY, AND XXXXXY KARYOTYPES HAVE A MORE
SEVERE PRESENTATION, AND MENTAL RETARDATION IS EXPECTED.

28. TURNER'S SYNDROME
ONLY 1 SEX CHROMOSOME IS PRESENT -X0, OR X_. THE EXPECTED Y CHROMOSOME
IS MISSING. TURNER SYNDROME IS ASSOCIATED WITH UNDERDEVELOPED OVARIES,
SHORT STATURE, WEBBED/.BULL NECK, AND BROAD CHEST. INDIVIDUALS ARE
STERILE, AND LACK EXPECTED SECONDARY SEXUAL CHARACTERISTICS. MENTAL
RETARDATION TYPICALLY NOT EVIDENT.

29. NORMALLY ASSOCIATED WITH 3 COPIES OF CHROMOSOME NUMBER 21 (TRISOMY OF
CHROMOSOME 21), RATHER THAN THE 2 FOUND NORMALLY. DOWN SYNDROME IS
CHARACTERIZED BY DIFFERING DEGREES OF MENTAL RETARDATION, A SKIN FOLD
OVER THE EYE, TYPICALLY SHORT STATURE, AND SHORT HANDS WITH A DEEP
CREASE IN THE PALM. DOWN IS ALSO KNOWN AS MONGOLISM (MONGOLOID).
Down's SyndromeDown's SyndromeDown's Syndrome
DOWN'S SYNDROME

30. BUTLER’S FIELD THEORY -
IT STATES THAT MAMMALIAN DENTITION CAN BE DIVIDED INTO SEVERAL
DEVELOPMENTAL FIELDS. THESE INCLUDE THE MOLAR/PREMOLAR FIELD, CANINE
AND THE INCISOR FIELDS. AMONG THE FIELDS, DENTAL VARIABILITY MANIFESTS
ITSELF STRONGLY MORE IN THE DISTAL THAN IN MESIAL DIRECTION., EXAMPLE, THE
LATERAL INCISOR IS MORE PRONE TO VARIATION, THAN THE CENTRAL INCISOR.
MONOZYGOTIC TWINS - TWO INDIVIDUALS DEVELOPED FROM A SINGLE FERTILIZED
OVUM. MONOZYGOTIC TWINS HAVE A GENETIC MAKE-UP IDENTICAL TO EACH
OTHER.
DIZYGOTIC TWINS – TWO INDIVIDUALS ARE DEVELOPED FROM TWO SEPARATE OVA,
OVULATED AND FERTILIZED AT THE SAME TIME. THE TWO OVA ARE FERTILIZED BY
TWO DIFFERENT SPERMS, HENCE ARE NOT GENETICALLY IDENTICAL.

31. DIZYGOTIC MONOZYGOTIC

32. ULTRASONOGRAPHY
(TWINS)

34. TWIN STUDIES ARE DONE BY ANALYZING MONOZYGOTIC AND DYZYGOTIC
TWINS IN A SPECIFIC MANNER. IN CASE OF MONOZYGOTIC TWINS, WHO
HAVE SAME GENETIC MAKE-UP, BUT POST NATALLY SOME MIGHT HAVE
DIFFERENT ENVIRONMENTAL CONDITIONS. THIS HELPS TO STUDY THE
EXPRESSION OF THE GENETIC FACTORS. AND DEVELOPMENT OF AN
INDIVIDUAL.
IN CASE OF DIZYGOTIC TWINS, WHO HAVE A SIMILAR ENVIRONMENTAL
CONDITION, THE INFLUENCE OF GENETIC AND ENVIRONMENT IN THE
EXPRESSION AND DEVELOPMENT OF AN INDIVIDUAL CAN BE STUDIED.
TWIN STUDIES HAVE SEVERAL LIMITATIONS LIKE IDENTIFICATION OF
DIFFERENT TYPES OF TWINS AS WELL AS THEIR DEVELOPMENTAL
ENVIRONMENT.
METHODS OF STUDYING ROLE OF GENES
TWIN STUDIES -

35. INBREEDING -
THE MODE OF TRANSMISSION OF CERTAIN TRAITS CAN BE STUDIED AND
THEIR DOMINANT AND RECESSIVE CHARACTERISTICS DETERMINED BY
ANALYZING CERTAIN COMMUNITIES WHERE PRACTICES LIKE POLYGAMY AND
‘MARRIAGES WITHIN THE FAMILY’ ARE PRESENT.
PEDIGREE STUDIES –
THESE ARE THE COMMONEST AMONG GENETIC STUDIES. HERE, A DEFINITE
TRAIT OF AN INDIVIDUAL IS STUDIED ALONG HIS ‘FAMILY TREE’ SO AS TO
FIND ANY HEREDITARY INFLUENCE. MANY OF THE FAMILY TRAITS LIKE
BIMAXILLARY PROTRUSION, MISSING TEETH, HIGH ARCHED PALATE ETC.
CAN READILY BE ATTRIBUTED TO HEREDITARY INHERITANCE. THE
DOMINANT AND RECESSIVE TRAITS AND THEIR EXPRESSIONS ALSO ARE
IMPORTANT IN DOING THESE STUDIES.

36. THANK YOU