Twin method 2 - 1

1876 Francis galton indicated the value of studying twins in genetic studies.

Siemens 1924 why did three uses of twins studies in reaserch

Heritability of traits is calculated by calculating concordance rate among twins. If there is high confidence in mono zycus queens then it is genetic trait. Vntr is inherited. 

Alternatively heritability is Vdz - Vmz/ Vdz

applied in the study of chromosomal aberrations, Cancer studies, cerebral palsy and mutations.

Shield 1972 study on schizophrenia show that concordance rate of monozygotic twins was 0.5 and dizygotic twins was 0.1.

CO twin in studies contribution in schizophrenia IQ

Limitations. No insight about the genes concerned and their mode of action. Also know idea about their transmission. many case studies have confidence rate below 50% which means environmental factors operate even before birth rate. Results are applicable only to the twins. Difficult to quantify trades like IQ

Placental method

Hardy weinberg method to calculate monozygotic twins by subtracting total twins from dizygotic twins. ( Gives number mz and dz within a population)