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In this medical video lecture at sqadia.com, Maham Afridi elaborates that many factors are involved in different patterns of inheritance. Environmental factors also play a role in multifactorial inheritance. She begins by explaining quantitative and qualitative traits, how phenotypic distribution of quantitative traits is measured. Furthermore, analytical techniques, heritability, and genetic segregation is also discussed in this lecture. Genotype x environment interactions is highlighted through examples. Alongside, mutational divergence in twins is discussed.
Quantitative VS Qualitative Traits
Monogenic traits result from the action of single gene. Several genes are involved in producing polygenic traits. Next, quantitative trait is described as a trait that can be considered into two or more phenotypic groups while quantitative trait is the one which can be measured through scale. Maham Afridi comprehensively explained these traits in the full length lecture for precise understanding.
Quantitative Phenotypic Distributions
In this section of lecture Maham Afridi elaborate how phenotypic distribution of quantitative traits is measured which include explanation of threshold characters, standard deviation and variance, and the empirical rule. The Empirical rule states that regardless of the trait under consideration, normal distribution is subdivided by standard deviation into predictable subgroups of a population.
Polygenic Inheritance and Heritability
Analytical techniques allow to identify some of the loci of quantitative traits. Heritability is a measure of the proportion of phenotypic variation that can be accounted for by genetic differences among members of the sample and its IQ test score is 0.60 in some populations. This term is symbolized as h2 because it is the ratio of two variances (s2). It is valid only in making predictions about genetic makeup.
Genotype X Environment Interactions
In this section, genotype x environment interactions are comprehensively discussed. Environmental differences and their influence is explained precisely with the help of example. Genetic heterogeneity refers to the situation in which a condition or disease could be traced to different underlying genotypes. Allelic heterogeneity refers to different alleles having distinctly different phenotypic consequences.
Concordance in Twins
Monozygotic twins share the same genotype and are also known as identical twins while dizygotic twins differ genetically like any other typical sibling pair. Dizygotic twins ae known as fraternal twins. Post conception mutations can occur and cause mutational divergence. MZ and DZ can be distinguished through tests like DNA fingerprinting.