Chp 3
Transcript of Chp 3
Hereditary Influences on Development
Chapter 3
Outline 1. Genetic Principles
2. Genetic Diseases
3. Genes X Environment
Genetics
Each cell in the human body has 46 chromosomes (23 pairs)
Chromosomes are filled with DNA = Genetic Blueprint
Genes
Specific segment of DNA, responsible for the production of a specific protein
Allele: Part of a gene; 2 alleles per gene
Genes Work in pairs
Homozygous (Same) Heterozygous (Different)
Basic Terminology XX = Female XY = Male
Genes
Genotype Set of genetic traits a person inherits;
the genetic blueprint
Phenotype Set of traits a person actually displays
Genes Dominant Genes
Recessive Genes
Genes Example of Dominant and
Recessive Genes (eye color, hair color)
Chromosome Abnormalities An error occurs during cell division
Down’s Syndrome (Trisomy 21), an extra 21st chromosome
Any changes in genetic info (extra or less) = Abnormality
Sex Chromosome Disorders 1. Turner Syndrome X_
2. Kleinfelter’s Syndrome XXY
3. Fragile X xX or xY
Single Gene Defects
1. Autosomal Recessive
Inherit recessive allele from both parents
E.G. PKU
2. Autosomal Dominant
Only need to inherit 1 allele, from either parent
E.G. Huntington’s Disease
3. Recessive genes on the X chromosome
Sex linked E.g. Hemophilia
Sickle Cell Anemia
Think about yourself: How sociable are you?
How athletic are you?
Models of Gene-Environment Interaction
Reaction Range (Gottesman)
Degree to which variations in the environment influence genotype
Behavioral Genetics
Robert Plomin
Studies the influence of genetic factors on behavioral traits
Gene-Environment Correlations
Scarr and McCartney (1983)
1. Passive 2. Evocative 3. Active
Behavioral Genetics
1. Twin Studies MZ vs DZ (Identical vs Fraternal)
Identical = 100% genetic similarity Fraternal = 50% genetic similarity
Behavioral Genetics
Heritability = Proportions of variance due to variations in genotypes
Behavioral Genetics
2. Adoption Studies
3. Family Studies E.G. Schizophrenia
Non-shared Environment Unique environment in which each
child (even in the same family) lives
Unique parent-child interaction Different school experiences Different peer group