Week Three – Genetics, Growth and Health
The human body has 46 chromosomes (23 pairs); these are tiny structures that contain genetic material; each pair are
called alleles and each pair can be different.
Autosomes: first 22 pairs; all same size; 23 pair determines sex of the child (XX = girl, XY = boy); same homosias,
Genotype: complete set of gene’s; persons heredity.
Phenotype: genetic instructions with environmental influences; tan = manipulated phenotype by environment;
individuals physical, behavioural and psychological features.
Dominant genes: expressed, chemical instructions are followed; can be seen in both homo and heterozygous.
Recessive genes: if paired with dominant gene, will not be expressed; only expressed when alleles are homozygous(the
Monozygotic Twins: identical twins; single fertilized egg that splits in two; share 100% of genes.
Dizygotic: fraternal twins; two separate fertilized eggs by two separate sperm; share 50% of genes.
Inherited: recessive/dominant/or sex chromosome; rare.
Abnormal number of chromosomes: extra, missing or damaged; more common; ex. downsyndrome, XXX syndrome.
Causes: abnormal number of chromosomes; extra 21 chromosome (autosome); carried by mother’s; 20 year old
mother – 1 in 1000, 40 year old mother – 1 in 50; causes cognitive deficits and developmental delays.
Physical features: head, neck and nose are smaller; almond shaped eyes; hearing, vision and other medical issues.
Learning – mild to moderate intellectual impairment; delays in speech; capable of developing various skills (slower pace
and may be different than other children when it comes to feeding, and dressing).
Supporting Children with DS
Early intervention: speech therapy, occupational therapy, and exercise for gross and fine motor skills will allow them to
live productive lives well into adulthood; benefits from special education and attention at school; many children can
integrate into regular classes at school.
1) Genes depend on environment
- Reaction range: genotype produces a range of phenotypes in reaction to the environment where
development occurs; ex. children with same intelligence but different environments, one will grow
to be smart due to stimulating environment.
2) Heredity and Environment
- Metaphor: clay and sculpture
- Genes are expressed or turned on during development; ex. genes initiate grey hair.
- Environment can trigger genetic expression; experiences can determine how and when genes are
turned on; ex. stress can induce grey hair. 3) Genes can influence environment child is exposed to
- Genotype can lead people to respond to child in a certain way; ex. bright and outgoing child vs shy
not so bright child.
- Niche picking: deliberately seeking out environment that fits ones heredity; develops as we become
independent; ex. social child seeks out social situations.
4) Environments make children within a family different
- Non shared environmental influences; environment affects each child in a unique way; may explain
differences in siblings; ex. parents more affectionate with one child; high grade standard with one
child, not the other; also consider environments outside of parents.
Cephalocaudal: head to tail; motor control of head Proximodistal: center outward; head, trunk and arm
comes before control of arms and legs; birth to 1 year: control comes before coordination of hands and fingers;
head and trunk grow faster then legs; 1 year – prenatal: chest and internal organs -> arms and legs ->
adolescence: legs grow most rapidly, accounting for hands and feet; infancy-childhood; infancy-childhood:
60% of height growth. arms and legs grow faster than hands and feet.
Secular growth trend: changes in physical development from one generation to the next; ex. children are taller than
previous generation; may result from better health and nutrition.
- 80% of growth hormone is secreted while children sleep; secreted from pituitary gland and triggers
muscle and bone growth
- Sleep less as we get older:
o 12 hours at age 3
o 10 hours at age 7
o 8 hours at age 12
- Lack of or inconsistent sleep affects cognitive processes and adjustment in school (pay less attention
in class, aggression, less sleep high BMI); use consistent bedtime routine to “wind down”.
- First two years of life are crucial because brain and body are growing rapidly; 25% of caloric intake is
needed for organ and body growth
- Preschoolers grow slower than infants and toddlers; need to eat less and watch intake, 1500-1700c
- School age children need to eat more to support growth and activities; 2400 calories per day
1) Eating a balanced diet: preschoolers like junkfood
2) Picky eaters: preschool years; solutions – allow and encourage choices in food but don’t force children to eat
them; never use food as rewards.
- 1 in 3 children under 5 years (globally); small for their age, shorter; lower intelligence; motor and