10.1 Genetics through Infancy (AP)

128803742	Identical twins	develop from the same fertilized egg (monozygotic) and therefore have the same genes
128803743	fraternal twins	develop from two eggs(dizygotic) fertilized by two different sperm
128803744	Chromosomes	a strand of hereditary material found in the nucleus of a cell
128803745	sex limited	a gene that affects one sex more strongly than the other, even though both sexes have the gene
128803746	sex chromosomes	determine if an individual will develop as a male or female
128803747	x chromosome	females have two per cell and males only have one
128803748	Y chromosome	males have one per cell and females have none
128803749	sex-linked	a gene located on the x chromosome
128803750	heritability	an estimate of the variance within a population that is due to heredity
128803751	Phenylketonuria (PKU)	an inherited disorder in which a person lacks the chemical reactions that convert a nutrient called phenylalanine into other chemicals; unless their diet is controlled the person will become mentally retarded
128803752	zygote	a fertilized egg cell
128803753	fetus	an organism more developed than the embryo but not yet born (from about 8 weeks after conception until birth in humans)
128803754	fetal alcohol syndrome	a condition marked by stunted growth of the head and body; malformations of the face heart and ears; and nervous system damage, including seizures, hyperactivity, learning disabilities and mental retardation
128803755	habituation	a decrease in a person's response to a stimulus after it has been presented repeatedly
128803756	dishabituation	an increase in the previously habituated response as a result of a change in the stimulus