Slide Handout - Biology and Behavior

Nature and Nurture
- Genotype: Inherited genetic material.
- Phenotype: Observed expression of genotype, including body characteristics and behavior.
- Environment: Everything beyond genes.

Parent Genotype -> Child Genotype
- Transmission of genetic material from parent to offspring.
Human Cell:
- Cell nucleus contains chromosomes.
- Chromosomes: Structures made of DNA, containing genes.

Allele: Each of the two forms of a gene, one from each parent at the same chromosome location.
- Homozygous: Two identical alleles.
- Heterozygous: Two different alleles.
Patterns of Inheritance:
- Dominant-Recessive
  - Under heterozygous conditions, the influence of only one allele is visible.
  - Dominant allele: Affects phenotype.
  - Recessive allele: Expressed only when paired with another recessive allele.
  - Carriers: Heterozygous individuals who can pass recessive traits.
- Examples of recessive-gene disorders:
  - Phenylketonuria (PKU)
  - Cystic Fibrosis.

Example: Two brown-haired parents (Bb x Bb) can have a blond-haired child (bb).
- B = Gene for Brown Hair, b = Gene for Blond Hair.
X-Linked Inheritance:
- A recessive gene is carried on the X chromosome.
- Males are more likely to be affected by X-linked conditions, such as color blindness and hemophilia.

Codominance: Both alleles in a heterozygous combination are expressed (e.g., sickle cell anemia).
Mutation: Sudden, permanent change in DNA (e.g., caused by radiation).
Polygenic Inheritance: Many traits influenced by multiple genes, especially evident in characteristics that exhibit gradations.

Gene-Environment Interaction:
- Also known as the Diathesis-Stress Model, this states that an inherited vulnerability and specific environmental conditions need to align to affect phenotype.
- Example: PKU.
Reciprocal Gene-Environment Model:
- Individuals with certain genes may seek environments that promote these genes' expression.
- Example: Adolescents with a genetic predisposition to depression may encounter stressors that lead to depression.

Study Focus: How genetic and environmental factors affect variation in behavior and development.
Heritability: Extent to which variability in a specific behavior in a population can be accounted for by genetic factors (range 0.0 to 1.0).

Fundamental Research Questions:
- Do behavior patterns run in families?
- How do children raised together compare to those raised apart?
Shared vs. Nonshared Environment Factors:
- Shared: Commonalities among family members.
- Nonshared: Unique aspects among family members.

Neurons: Cells of the nervous system, responsible for information storage and message transmission, consisting of:
- Cell body
- Dendrites
- Axon
- Terminal buttons.
Nerve Impulse:
- When dendrites or cell body is stimulated, travels down axon to terminal buttons.
- Synapse: The gap between neurons.
Neurogenesis: The proliferation of neurons through cell division.
Programmed Cell Death: Not all neurons survive; 20-80% can die as synapses form.
Synaptic Pruning: Excess neurons that are unstimulated lose synapses.

While neurons decrease post-synaptic pruning, the brain can still increase in size during childhood due to glial cells, which:
- Form a myelin sheath around certain axons.
- Myelin Sheath: Fatty structure that insulates axons, increasing the speed and efficiency of information transmission (grows rapidly until age 2).

Cerebral Cortex: The largest and most complex brain structure that is last to stop growing and is influenced by the environment.
Regions develop based on the emergence of capacities.

Cerebral Hemispheres: Two halves of the cerebral cortex communicating through the corpus callosum, specialized for different processing:
- Left Hemisphere: Controls the right side of the body, verbal abilities, positive emotion.
- Right Hemisphere: Controls the left side of the body, spatial abilities, negative emotion.
Plasticity: The brain's ability to be altered by experience, categorized as:
- Experience-Expectant: Dependent on ordinary experiences during critical periods for shaping brain development.
- Experience-Dependent: Neural connections created and reorganized throughout life based on experiences, irrespective of timing.

Timing after brain damage is crucial for recovery.
Due to plasticity, the brain can rewire itself post-damage, extent of which depends on the severity of damage.

Height and Growth Rate: Predominantly determined by heredity, especially in the absence of severe negative environmental influences.
Catch-Up Growth: Physical growth returns to a genetically determined path when environmental conditions improve.

Food Preferences: Picky eating habits often begin around age two, and children may suffer from food neophobia, an aversion to unfamiliar foods.
- Importance of repeated exposure to a variety of foods emphasized.
Breastfeeding: Recommended until age two with solid foods introduced at six months.
- Advantages include immunity, lack of bacteria, and providing antibodies.

Defined as not having enough food, contributing to nearly half of all deaths in children under five worldwide (UNICEF).
Impacts all aspects of development, with specific conditions such as marasmus and kwashiorkor linked to it.

Condition where infants become malnourished and fail to gain weight, characterized by wasting, stunting, and apathy or withdrawal.
Prevalence rate in US primary care child patients is about 5-10%.
Organic: Medical causes of FTT.
Non-Organic: Caused by lack of affection/stimulation or inability to produce breast milk (90% of all cases).