ch 14 pt 5

• infertility


  inability of a young couple to become pregnant despite having frequent intercourse for more than a year
• ART


  fertility treatment in which either eggs or embryos are handled, surgically removing eggs form a womans ovaries combining them with sperm in the lab and returning it to the woman's body or donating it to another woman
• IVF


  egg and sperm are retrieved from the male and female and placed in a fluid within a petri dish where fertilization occurs. once the zygotes start dividing the embryo gets surgically transferred to the female uterus
• what was a substantial problem that initially hindered in vitro fertilization techniques

  they were not aware of sperm capacitation
• intracytoplasmic sperm injection (ICI)

  a single sperm is injected into the cytoplasm of an egg the zygotes divide and the embryos that appear healthiest after 3 divisions are considered for implanting into the uterus
• what is the number one cause of infant death in the US

  inviable/unhealthy phenotypes & congenital malformations
• 3 major pathways that lead to disorders of development

  1. genetic alternations- mutations in genes or changes in the number of chromosomes
  2. environmental mechanisms- chemicals from outside the body causes deleterius phenotypic changes by inhibiting developmental signals
  3. random events- chance, some developmental anomalies are "bad luck"
• pleiotropy


  the production of several effects by a single gene or pair of genes
• mosaic pleiotropy


  different effect are produced independently as the result of the same gene being critical in different parts of the body (ex: KIT gene)
• relational pleiotropy


  defective gene in one or more parts of the embryo causes a defect in another part even though the gene is not expressed in the second tissue (ex: MITF expression failure)
• heterogeneity


  production of similar phenotypes by mutations in different genes (SCF & KIT, cyclopia)
• phenotypic heterogeneity


  the same mutation producing different phenotypes in different individuals (FGFR3 & genes producing myosin-7)
• preimplantation genetic diagnosis (PGD)


  testing for particular genetic mutation or chromosomal anomaly
• why is maximum fetal susceptibility to teratogens occuring between weeks 3-8? why is the nervous system an exception to this?

  because most organ systems form during the embryonic period and the fetal period is one of growth and remodeling. the nervous system is an exception because it forms over the entire course of development
• two ways in which teratogens exert their effects

  1. disrupt development
  2. promoting development at a time or place that is not appropriate
• FAS vs FASD


  FAS- babies have small head size, indistinct philtrum, a narrow vermillion border on the upper lip and a low nose bridge. the brains are smaller and show poor development

  FASD- encompass all of the alcohol-induced malformations and functional deficits that occur
• endocrine disruptor and how are they different from teratogens?

  endocrine disruptor are exogenous chemicals that disrupt development by interferring with the normal function of hormones. the anatomical alterations induced by endocrine disruptors are microscopic, they arent obvious like the teratogens
• fertility vs fecundity 


  fertility- actual number of offspring produced by an individual

  fecundity- ability to produce an abundance of offspring or new growth, the possible number of offspring that can be produced over a lifetime