I. genes: units of heredity
1. chromosomes: genes are aligned on chromosomes
A. humans have 23 pairs of chromosomes
a. 22 pairs are autosomal: both sexes
have these
b. 1 pair is sex linked & are designated
X & Y
-genetic males have XY
-genetic females have XX
B. genes are aligned in pairs on chromosomes
a. homozygous: an identical pair
b. heterozygous: non-identical pair
2. some genes are dominant & others recessive
A. dominant genes: always are expressed (i.e., effects
behavior & phys. characteristics)
B. recessive genes: only expressed when they
are homozygous
3. partial penetrance: genes that are expressed only in certain
environments
4. sources of genetic variation
A. recombination (at fertilization)
B. nutation
II. only heredity & environment can shape our brains, the chemicals
they produce, & thus
our thoughts & behaviors
A. If you accept the above statement, how would
you explain the notion that humans
have free will?
2. How do we study the influence of heredity?
A. examining monozygotic (identical) and dizygotic
(fraternal) twins
B. examining adopted kids & their genetic &
adoptive parents