BIOSC 0160 Lecture Notes - Lecture 7: Twin, Genetic Variation, Prefrontal Cortex
Document Summary
Dizygotic twins: when two separate sperm fertilize two separate eggs and babies grow in separate embryonic sacks. Theses siblings share 50% of their genes and can be either male/female or same-sex. Monozygotic twins: one sperm fertilizes one egg and the embryo splits within 3-13 days of fertilization so the two babies grow in the same embryonic sack. 100% of their genes and can only be male/male or female/female. Genetically the twins are completely identical because they have the same genome, but environmental upbringing leads to differences in personality. Observing the correlation congruence of a specific trait between dizygotic twins and monozygotic twins can help understand to what extend traits are genetically influenced. If there is a consistently stronger congruence of a trait among monozygotic twins than among dizygotic, it is likely tied to their shared genes. Genetic variation can come from mutations, cross over, and activation of different genes on a cell by cell basis via methylation.
