CH 4 Summary Flashcards
Genes are chemicals that maintain their integrity from one generation to the next and influence the development of the individual.
A dominant gene affects development regardless of whether a person has pairs of that gene or only a single copy per cell. A recessive gene affects development only in the absence of the dominant gene.
Genes can change by
mutations, microduplications, and microdeletions.
Gene expression can also change in a process called epigenetics, as chemicals activate or deactivate parts of chromosomes.
Experiences can cause epigenetic changes, and in some cases an epigenetic change can influence the next generation.
Most behavioral variations reflect the combined influences of genes and environmental factors.
Heritability is an estimate of the amount of variation that is due to genetic variation as opposed to environmental variation.
Researchers estimate heritability of a human condition by comparing monozygotic and dizygotic twins and by comparing adopted children to their biological and adoptive parents.
They also search for genes that are more common in people with one type of behavior than another.
Even if some behavior shows high heritability for a given population
a change in the environment might significantly alter the behavioral outcome.
Genes influence behavior directly by
altering brain chemicals and indirectly by affecting other aspects of the body and therefore the way other people react to us.
The process of evolution through natural selection is a necessary outcome, given what we know about reproduction:
Mutations sometimes occur in genes, and individuals with certain sets of genes reproduce more successfully than others do.
Evolution spreads the genes of the individuals who have reproduced the most.
Therefore, if some characteristic is widespread within a population, it is reasonable to look for ways in which that characteristic is or has been adaptive. However, we need to evaluate the relative contributions of genetics and cultural influences.
