Genetic Inheritance

Genetic Inheritance • Conception • The union of sperm and ovum create a zygote • The zygote contains a complete set of 46 chromosomes • The first 22 pairs are called autosomes. • The 23rd pair are the sex chromosomes. • DNA • Genes

Genetic Principles • Genes • Genotype. • Phenotype • Reaction range • Alleles • Homozygous Alleles (similar) • Heterozygous Alleles (different) • dominant - recessivegene principle • incomplete dominance (blending) • codominance (type AB blood)

Genetic Inheritance • Single Gene-Pair Inheritance • Polygenetic Inheritance • Genetic Imprinting • Genes are (chemically marked) in one of the parents and have different effects depending on which parent carries it. • Huntington disease manifests earlier if passed on by the male • Asthma / females , Diabetes / males

Genetic Inheritance • Sex Linked Genes or Traits (X-linked inheritance) • ex: hemophilia, red/green color blindness • Mutations • A sudden, permanent alteration in DNA • occurs spontaneously or by environmental hazards • Chromosomal Abnormalities • Often the result of the 46 chromosomes not being divided equally (too many or too few) • Down Syndrome

Genetics & Environment Heritability: The amount of variability in a population on some trait dimension that is attributable to genetic differences among those individuals

Gene-Environment Relationships • Epigenetic View: Heredity  Environment • Passive Gene-Environment Relation • Evocative Gene-Environment Relation • Active Gene-Environment Relation • Shared and Non-shared Experiences

Stages of Prenatal Development

Germinal Stage (Weeks 1-2) • The zygote, begins to divide, and travels down the fallopian tube. • The new cells form the blastocyst, which attaches itself to the uterine wall • The blastocyst forms several layers of cells • The outer cells (trophoblast) form the placenta.

Embryonic Stage (weeks 3 – 8) • The inner cells of the blastocyst which will become the embryo differentiate into three layers: • Ectoderm: Outermost layer which will become skin, hair, nails, the nervous system, and sensory receptors • Mesoderm: Middle layer which will develop into the circulatory system, bones, muscles, excretory and reproductive system • Endoderm: Undermost layer which will develop into the digestive and respiratory systems

Embryonic Stage (weeks 3 – 8) • The formation of organs begins (organogenesis) • Sexual differentiation takes place around the 7th or 8th week • By the end of the embryonic stage about 95% of body parts and systems have begun development.

Fetal Stage (Week 9-Birth) • This period involves the dramatic increase in body size and completion of all physical structures • Age of viability = approx. week 25

Prenatal Growth • Occurs in three patterns: • Orthogenic • Cells are all the same and then differentiate • Cephalocaudal: • Latin for “from head to tail”. • Proximodistal: • Latin for “from near to far”.

Influences on Prenatal Development • Nutrition • Stress • Mother’s Emotional state • Mother’s Age • Nearly 50% of pregnancies among women in their 40’s and 50’s result in miscarriage. • Father

Influences on Prenatal Development • Teratogans are any disease, drugs, or other environmental agents that can cause damage to a developing fetus. • Effects depend on: • Dose • Heredity • Presence of other teratogens • Age of child • Sensitive period

Postnatal (Postpartum) Depression • Occurs in 1/10 new mothers • Effects bonding and initial care of child • Effects on mother • May not want child • Mood lability and other symptoms of depression • Psychosis • SI / HI

Postnatal (Postpartum) Depression • Effects on child • Susceptibility • Past episode(s) of post partum (30 to 50% chance with each subsequent delivery) • Personal past history of a mood disorder • Family history of Bipolar disorder (even if not personally experienced)

Genetic Inheritance