A short presentation about the dominant (genetic) allele for the use of the dominant hand ie being right handed or left handed.

1. HANDEDNESS

2. HANDEDNESS
• BETTER, FASTER OR MORE PRECISE PERFORMANCE OR INDIVIDUAL
PREFERENCE FOR USE IF A HAND KNOWN AS DOMINANT HAND.
• THE LESS PREFERRED HAND IS CALLED THE NON DOMIANT HAND.

3. TYPES
• RIGHT HANDEDNESS
-THE MOST COMMON KIND
-70-90% OF THE WORLD POPULATION
• LEFT HANDEDNESS
-FAR LESS COMMON
-APPROXIMATELY 10% OF THE WORLD POPULATION
• CROSS DOMINANCE/ MIXED HANDEDNESS
-CHANGE OF HAND PREFERENCE BETWEEN TASKS
-VERY UNCOMMON
-ABOUT 1% PREVALENCE
• AMBIDEXTERITY
-EQUAL ABILITY TO USE BOTH HANDS
-THOSE WHO LEARN IT STILL TEND TO FAVOR THEIR ORIGINAL DOMINANT HAND

5. CAUSES
• DIVISION OF LABOR
-SPEAKING AND HANDIWORK REQUIRE FINE MOTOR SKILLS.
-CENTREVFOR VERBAL PROCESSING AND HANDIWORK ARE
CONTROLLED BY LEFT HEMISPHERE OF THE BRAIN AND VISUOSPATIAL
PROCESSING IS DONE BY RIGHT HEMISPHERE
-THEREFORE RIGHT HANDEDNESS PREDOMINANTS
-LEFT HANDEDNESS HAVE A HETEROGENOUS BRAIN ORGANIZATION
-LEFT HANDERS ARE LESS LATERALIZED

6. • GENETIC FACTORS
-COMPLEX INHERITANCE PATERN
-A POLYGENIC TRAIT
-BASED ON A GENOME WIDE ASSOCIATION STUDY IT WAS FOUND THAT AT
LEAST 40 LOCI CONTRIBUTE IN DETERMINING THE TRAIT OF LEFT
HANDEDNESS
-LRRTMI A BRAIN EXPRESSED IMPRINT GENE INHERITED FROM PATERNAL
SIDE WHICH IS PRESENT ON 2p12 ENCODED LEUCINE RICH REPEAT
TRANSMEMBRANE PROTEIN
-CAG REPEAT LENGTH IN X LINKED ANDROGEN RECEPTORS HAS OPPOSITE
EFFECT ON PROBABILITY OF LEFT HANDEDNESS IN MALE AND FEMALE
-PCSK6 (PROTEIN CONVERTASE SUBTILISIN/ KEXIN TYPE 6) A PROTEASE
CLEAVES NODAL PROPROTEIN WHICH DETERMINES LEFT AND RIGHT
SYMMETERY IN BILATERALS FROM MOLLUSC TO VERTEBRATES AND
HANDEDNESS IN HUMANS

7. • EPIGENETIC FACTORS
-25% OF VARIANCE FACTOR AND 75% OF ENVIROMENTAL FACTORS
-ASYMMETRIC METHYLATION OF CpG
• PRENATAL HORMONES
-EXPOSURE TO DIETHYLSTIBESTROL (SYNTHETIC ESTROGEN) CAUSED LEFT
HANDEDNESS
• PRENATAL VESTIBULAR SYMMETRY
-POSITION OF FETUS IN FINAL TRIMESTER AND SUBSEQUENT BIRTH POSITION
-2/3rd OF FETUSES PRESENT WITH THEIR LEFT OCCIPUT ARE LEFT HANDED
-PREMATURITY RESULTS IN DECREASE IN RIGHT HANDEDNESS

8. CORRELATION WITH OTHER FACTORS
• INTELLIGENCE
-IQ DIFFERENCE OF 1.5
-MORE DEVELOPED LANGUAGE CENTERS IN BRAIN
-MORE SKILLED MUSICANS AND MATHEMATICIANS
• HEALTH
-LOWER BRITH WEIGHT
-NEUROPSYCHIATRIC AND DEVELOPMENT DISORDERS SUCH AS DEPRESSION,
BIPOLAR DISORDER, ALCOHOLISM, ETC
-40% CHILDREN WITH CEREBRAL PALSY WERE LEFT HANDED
-62% INCREASED RISK OF PARKINSON AND BREAST CANCER IN WOMEN

9. • GENDER
-MALE TO FEMALE RATIO 1.23
-23% MORE MALES ARE LEFT HANDED COMPARED TO FEMALES
(DATA COLLECTED FROM 1,787,629 INDIVIDUALS)

10. INTERNATIONAL LEFT HANDERS DAY
• 13th AUGUST
• left-handers everywhere can celebrate their sinistrality (left-
handedness) and increase public awareness of the advantages and
disadvantages of being left-handed. It celebrates their uniqueness
and differences, who are from seven to ten percent of the world's
population.