PSYCH 1XX3 Lecture Notes - Lecture 2: Twin Study, Phenotypic Trait, Eye Color
24 Jan 2018
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Document Summary
The zygote quickly divides into billions of different cells. Each parent can produce millions of genetically distinct offspring. Males determine the sex of their child (23rd chromosome determine the gender) Phenotype - expression of an individual"s genotype in terms of observable characteristics. Genotypes can express into different forms of phenotypes. There are four main patterns of genetic expression: simple dominant-recessive inheritance - pattern of inheritance in which the expression of a trait is determined by a single pair of alleles. Homozygous: when two alleles have the same effect on the phenotype. Heterozygous: when two alleles have a different effect on the phenotype. A phenotypic trait is often governed by multiple pairs of genes: polygenetic inheritance - the expression of a trait is determined by the interaction of multiple genes. No single gene can account for most complex behaviours. E. g. eye colour: codominance - when the expression of a trait is determined equally by two dominant alleles.
