AP PSYCH 6.1 The Lifespan and Physical Development in Childhood

Stages of Development

The zygote is a fertilized egg
It undergoes rapid cell division
The cells have XX or XY 23rd chromosomes
- This determines the sex, which is in turn determined by the father’s genotype
- Sometimes the 23rd chromosomes are not either of that pair, resulting in an intersex infant
At this stage, there is the least susceptibility to environmental influences
This stage lasts from conception to two weeks

Phenylketonuria (PKU) is an inability to produce enzymes to digest proteins
- This is an inherited disorder
- Causes neurological impairment
Down syndrome occurs due to a trisomy of chromosome 21
- Not usually inherited, likely caused by gene copying error
- Physical growth delays and intellectual disabilities
Note that genotype relates to genetic characteristics and phenotype relates to physical characteristics

The sac that encases a child from cellular stage to fetus
It is also the method of delivery for nutrients from the mother to the fetus
Whatever the mother breathes, eats, or drinks can pass through the placenta and alter the course of development
Teratogens are any environmental agent that can reach the embryo or fetus during prenatal development and cause harm
- Alcohol causes fetal alcohol syndrome, susceptibility to alcohol later in life, neurological and physical impairments
- Tobacco can cause a cleft palate, and low birth weight