Heritability coefficient: The extent to which differences between people reflect heredity. Different coefficients for different traits, some might be more heritable than others. Certain heritability coefficients are going to differ in different environments. Example: children with well educated parents are likely to have a stimulating and educational environment, and so heritability of learning disabilities is higher in children with well educated parents. Therefore, learning disability is less explained by environment and more explained by genetics. Reaction Range : The range of phenotypes that could occur in the case of the same genotype. The range of phenotypes that the same genotype may produce in reaction to the environment where development takes place. Example: PKU Caused by a recessive gene on chromosome 12. Homozygous recessive genes on both genes on chromosome 12. Children lack the enzyme that breaks down phenylalanine, found in eggs, mean, cheese. If they cant break it down, then PL will build up in the body and can cause damage to the nervous system. If certain foods are avoided, children will not experience damage. After age 12, they no longer need to be on the diet. Even though they have a specific genotype, the phenotype is going to depend on the environment they are in, which shows the reaction range from damage to no damage. Epigenesis: Continuous interplay between genes and environment that drives development. Environment can actually have a physical effect on DNA. Methylation: Physical change (in DNA) in the genetic expression. This change OCCURS based on the environment. Methyl groups can be added to certain genes and these genes are essentially turned on or off based on if methylation is present or not. Methylation usually stops certain genes from being expressed and doesnt necessarily have much to do with unlocking genes. Niche Picking: A child deliberately picks an environment that suits ones heredity. Intelligent- likely seek more mental stimulation, outgoing- seek more people to be around. Prenatal Development At the day of conception is when the sperm penetrates the egg At 4 days, creates a blastocyst composed of 100 cells that looks like a hollow ball 7 days: implant into uterine wall and are called an embryo 3-8 weeks: cell specialization, into different types of cells. 3 main layers, endoderm (digestive, thyroid, organs), mesoderm (middle layer, muscle, blood, cartilage), ectoderm (skin, neurons, pigment cells). At this point, embryo is in amniotic sac in amniotic fluid and is being fed by placenta through umbilical cord. 4 weeks: When the neural tube closes, neural plate is going to turn into the neural tube. Notochord drives process, and made of cartilage, and the notochord is a skeletal rod that supports the structure of the embryo, and drives the closing of the neural plate. The neural plate is part of the ectoderm. The neural tube falls below the ectoderm. So then we have the ectoderm surrounding the mesoderm, the endoderm, and the neural tube. The neural tube becomes the spinal chord, with one end of it becoming the brain. The ectoderm becomes the skin, epidermis.
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- Fall '13
- Zygosity, Phenylketonuria