Download - Biological Beginnings
Chapter 2: Biological Beginnings
Genetic FoundationsHeredity & Environment
Evolutionary Psychology
Evolution is a theory.
Survival of the fittest does not necessarily imply evolution, only a healthy population.
Natural selection based on adaptability is a circular argument.
Evolutionary Psychology
Evolutionary psychology is not new.
Popular in the early 1900’s
5000+ instincts were named
Proved to be a dead-end path
Evolutionary Psychology:Theory based on a theory
David Buss (1995, 2004) Males and females of the human species evolved
differently (e.g., spatial skills, sex) Must assume that skills are inborn or that learning
and experience changes genes in human gametes (egg/sperm)
Family curse Feminists
Evolutionary Developmental Psychology
Theory based on a theory based on a theory.
Extended juvenile period evolved so that we could learn to cope with society.
Or did society “evolve” to cope with the juvenile period?
Evolutionary Psychology Evolutionary Developmental Psychology
Human characteristics are not random. They are age and gender related.
Order and purpose are not related to random evolution, but imply the action of intelligence.
Part of the confusion has to do with teleology.
Evolutionary Developmental Psychology
Perspective here has profound effects on:
Concern for the tradition of learning/socialization
Judith Harris (Nature Assumption, 1998) says parents not important; genes and peers rule.
Views of the meaning of life
was man made for nature/society or nature for man
Genetic Foundations
DNA (deoxyribonucleic acid) a complex molecule containing the genetic
information that makes up the chromosomes
has two strands-forming a “double helix”- held together by bonds between pairs of nucleotides (spiral staircase)
Chromosomes threadlike structures made of DNA molecules that contain the genes
Genetic Foundations
Chromosomes
Human beings have 46 chromosomes (23 pairs)
Entire DNA code/set of chromosomes is repeated in each of the cells
Define the limits of species variation; separate species
Genetic Foundations
Chromosomes: limits
“Each of us carries a “genetic code” that we inherited from our parents. Because a fertilized egg carries this human code, a fertilized human egg cannot grow into an egret, eagle, or elephant.”
Genes: Our Biological Blueprint
Genes the biochemical units of heredity that make up
the chromosomes a segment of DNA capable of synthesizing a
protein
Genome the complete instructions for making an organism
Proteins are the cell building blocks and bodily process regulators
Genetics and Behavior
Nucleus Chromosome Gene
Cell DNA
Genes: Our Biological Blueprint
Human Genome Project Completed about 2000 Humans have 20,000 – 25, 000 genes (21,667) There are far more proteins than genes – 10-20 million Genes (DNA) are dependent- collaborate with other
sources of information Gene expression/activity is affected by context or
environment Context is affected by hormones, light, nutrition, etc.
Genetic Foundations
99.1% of DNA within the human race is identical
98-99% of human and chimpanzee DNA is identical
Cell Division – Gamete Production
Mitosis (normal cell division) – the nucleus of the cell & the chromosomes duplicate and divide into 2 cells. Each has the same 23 pairs of chromosomes.
Gametes (sperm and ova) have only 23 chromosomes
They are formed by meiosis rather than mitosis.
At conception, these two unite resulting in a full complement of 46 chromosomes.
A fertilized egg is called a zygote.
The Sex Cells
• Alleles are normal variations of a gene, found at the same location.
• A child who inherits the same allele (type of gene) from both parents is homozygous for that trait.
• A child who inherits different alleles from each parent is heterozygous for that trait.
Sources of Variation
Crossing over – chromosomes pair up and exchange segments during meiosis.
The probability of genetically identical, non-twin siblings is 1 in 700 trillion.
Sources of Variation
Genetic ExpressionInfluenced by the environment
hormoneslightnutritionbehaviorstress (cortisol may cause a fivefold increase in DNA damage)
Sources of Variation
Genetic Foundations
Genotype – genetic composition
Phenotype – observable characteristics
• Patterns of Genetic Inheritance•
Dominant-recessive: the dominant gene (allele) will determine the characteristic
Sources of Variation
• Patterns of Genetic Inheritance•
Dominant-recessive: the dominant gene (allele) will determine the characteristic
Sources of Variation
• Examples of dominant genes Dark hair, curly hair, dimples,
types A & B blood (vs. type O), traits for normality in vision, hearing, pigmentation, etc.
Huntington’s Disease
Patterns of Genetic InheritanceDominant-recessive inheritance
• Examples of recessive genes: Cystic fibrosis, PKU, Tay-sachs
disease. Sickle-cell anemia
Patterns of Genetic InheritanceDominant-recessive inheritance
• Co-dominance: both alleles contribute to the phenotype
• Additive: they contribute equally
• Example of Co-dominance; Sickle-cell anemia
Patterns of Genetic InheritanceCo-dominance and Additive
X-linked or Sex-linked Inheritance
Humans have 23 pairs (46 total) of chromosomes – 22 pairs are autosomes; the 23rd pair is XX in females and XY in males
• Females - X chromosome from father to match the mother’s X
• Males - Y from the father, does not have all the same genes
• Defective gene on mother’s X is offset in females, but not in males
• Examples: hemophilia, RG colorblindness
Patterns of Genetic InheritanceX-linked (sex-linked) inheritance
• Genes are chemically marked so that one member of the pair is activated regardless of its makeup.
• Important whether the trait is inherited from the mother or father.
• Examples: asthma, allergies, Huntington’s , diabetes
Sex-linked Genetic InheritanceGenetic Imprinting
Patterns of Inheritance - Polygenic
Many genes interact to influence the characteristic
Most psychological characteristics are polygenic
(Where environmental factors are included, traits are said to be multi-factorial.)
Usually happen during meiosis
Involve breakage and failure to separate
Most common are Down syndrome (trisomy 21) (1 in 700-800 live births) and sex-linked
May be mosaic (not all body cells defective)
Often result in miscarriage
Chromosomal Abnormalities
Chromosomal Abnormalities
Down Syndrome Trisomy 21: extra copy of a chromosome on the
21st pair Round face, flattened skull, potruding tongue,extra fold of skin
on eyelids, short limbs Mental and motor retardation
More common to older mothers, rare among African Americans
• Gene damaged on X chromosome
• Most common inherited cause of mild to moderate mental retardation
• Linked to autism• More common in males
Chromosomal AbnormalitiesSex-linked - Fragile X
XXY (Klinefelter) may have verbal difficulties. Tall, underdeveloped testes, possible breasts. 1/800 live male births.
XO (Turner) have trouble with math and spatial skills. Short and have webbed neck; may be infertile. 1/2500 live female births
XYY (Are they more aggressive, antisocial?)
Sex Chromosome Abnormalities
Gene-linked Abnormalities
Over 7000 known (most rare), including: Cystic fibrosis Diabetes Hemophilia Huntington PKU (phenylketonuria) Sickle-cell anemia Spina bifida Tay-sachs disease
Genetic Counseling – for whom?
Family history of disease, mental retardation, physical defects
History of miscarriages
Mother over age 35 (rate of abnormality begins to rise sharply)
May cause miscarriage (except ultrasound, maternal blood samples)
Is the problem correctible?
Genetic engineering is still in the future.
Often the only decision is whether or not to abort the fetus.
Prenatal Diagnostic Methods
Chorionic villi sampling (6-8 weeks);detects genetic defects; risk of miscarriage, limb deformity
Amniocentesis – (11 weeks, best after 15 weeks); detects genetic defects; smaller risk of miscarriage
Prenatal Diagnostic Methods
Fetoscopy – tube with light inserted into uterus; 15-18 weeks; limb & facial defects; some diseases & neural defects; some risk of miscarriage
Preimplantation genetic diagnosis –
Associated with in-vitro fertilization
Prenatal Diagnostic Methods
Infertility
1 in 6 couples in U.S. Waiting too late Sexually transmitted diseases
Fertility technology (IVF, donors) Adoption
Babies culturally unavailable
Environmental Influence
Environmental Influence
Rats reared in an environment enriched with playthings show increased development of the cerebral cortex
Impoverished environment
Enriched environment
Environmental Influence
Culture the enduring behaviors, ideas, attitudes,
and traditions shared by a large group of people and transmitted from one generation to the next
Norm an understood rule to accepted and
expected behavior norms prescribe “proper” behavior
Twins Identical Twins
develop from a single fertilized egg that splits in two, creating two genetically identical organisms
Fraternal Twins develop from separate eggs genetically no closer than
brothers and sisters, but they share a fetal environment
Identicaltwins
Fraternaltwins
Samesex only
Same oropposite sex
Dizigotic (two zygotes) Share approximately 50% of their
genetic heritage like any two siblings.
Major causes are maternal age and fertility drugs.
Twinning dramatically on the increase since the 1970s.
Multiple Births – fraternal twins
Multiple Births – identical twins
Monozygotic – one zygote (same fertilized egg)
Share 100% of genetic heritage
Occurs about 3 per 1000 live births worldwide
Factors may include temperature and oxygen levels and late fertilization
Genetics Research
Behavior Genetics
study of the power and limits of genetic and environmental influences on behavior
Molecular Genetics subfield of biology that studies the
molecular structure and function of genes
Nature-nurture Research
• Molecular genetics Human Genome Project
• Behavioral genetics Twin studies
Equal environment assumptions Adoption studies Concordance rates
Epigenesis – ongoing nature/nurture exchanges (bi-directional)
Reaction range
Canalization
Genetic-environmental correlation• Passive• Evocative• Active (niche-picking)