Genetic Engineering o Human Genome Project Chapter 3 Prenatal Development The Human Genome Project is an international effort to map the entire human genome It has already revealed a great deal about the nature of genes and genetic variations Inheritance of harmful recessive genes and abnormalities of the chromosomes are major causes of serious developmental problems o Genetic Counseling Results are an estimate of risk not a guarantee that a disorder will or won t occur Genetic counseling and prenatal diagnosis help people at risk for transmitting hereditary disorders Assess their changes of giving birth to a healthy baby Provides facts Recommended for Individuals with a close relative with a genetic condition Women over 30 and men over 40 Couples with a history of infertility Genetic Counseling Decision Tree for High Risk Couples Doesn t tell you what to do but it takes you through the decision tree and helps you make the best decision for you Creation Connections Main characters Ovum and Sperm o Main characters 1 Ovum from ovaries travel into fallopian tubes 2 Sperm produced in a male s testes 3 Intercourse sperm travel through the cervix fallopian tube 4 Possible results fertilization FYI Sperm can remain viable for up to 6 days Prenatal development o Divided into 3 periods Period Length Key Events Zygote AKA Germinal 2 weeks Embryo Embryonic 6 weeks Fetus Fetal 30 weeks Periods of Prenatal Development o The Germinal Period 0 2 weeks Overview The Period of the Zygote Fertilization cell differentiation blastocyst exo and endoderm implantation start of placenta Specialized layer of cells endoderm organs begin to develop heart beats primitive streak nuerogenesis development of arms legs face organs and muscles Growth and Finishing brain development neurons and CNS learning From conception to attachment o Conception occurs in fallopian tubes o Cell differentiation and multiplication o After fertilization cell mass drifts out of the fallopian tubes o Implantation it takes about 7 10 days for the zygote to imbed itself into the uterine wall endometrium The process begins at the end of the first week and is completed by the end of the second week Highly canalized o 30 don t survive o 42 successfully implant in uterus Around the 4th 5th day 60 to 70 cells exist forming a hollow fluid filled ball called a blastocyst At the end of 1st week differentiation o Occurs in the original stem cells o Embryo s cells have formed specialized layers Conception and Implantation Outer layer cells will become support system Will become structures that enable the embryo to survive Ex placenta Placenta via umbilical cord o Provides nutrients and oxygen o Carries waste products away Blastocyst Inner Cell Mass Embryonic Disk will become embryo o With 3 specialized layers formed between 7 16 days Outer layer Ectoderm becomes external coverings E g Skin hair sense organs nervous system epidermis tooth enamel Inner layer Endoderm becomes digestive system respiratory system and lungs and glands Middle layer Mesoderm develops into muscles and bones connective tissues and circulatory system Develops around 16 days As development continues o Tiny finger like villi blood vessels form burrow into uterine wall efficiently o Independent before now gets nutrients o Allows developing organism to receive nutrients more o Placenta starts to develop connected to the developing organism by the umbilical cord o The Embryonic Period 3 8 weeks Major organs develop begin to function Rate of cell differentiation intensifies Support systems for cells form organs appear Each organ system has it s own program for development Heart first Lungs last Each system s development follows a particular sequence Different parts develop on different days Day 31 shoulders arms and hands develop Day 33 fingers develop Day 34 36 thumb is complete Primitive streak appears Thin line down the center of the embryo which becomes the central nervous system CNS Heart is first organ to function Circulates blood to the placenta throughout body by end of 3rd week By end of 1st month Ears nose mouth begin to form Arms legs make appearance as buds Fingers toes become defined Internal organs rapidly developing o Stomach produces digestive juices o Kidneys filter blood During this time of extremely rapid growth organism is most vulnerable to environmental insult Neurogenesis the production of nerve cells neurons begins Almost all of the neurons in the brain are generated prenatally By the end between 1 2 long All major organ systems have formed o The Fetal Period 9 weeks birth Sex organs develop Brain development is significant Age of viability occurs around 22 weeks Weight plays a crucial role Only 20 under 1 5 pounds survive By 28 weeks survival rate is 95 The Fetus Week Eight to Birth Size of fetus increases twentyfold Brain development Age of viability is the age at which a preterm newborn might survive o Some neurons die off as others make new connections o CNS becomes active and responsive in mid pregnancy o Fetal activity random at first spontaneous movements begin at about 4 months o Prenatal behavior activity shapes further brain development Fetus brain sending signals to muscles and muscles are responding o Ex 6 month breathing amniotic fluid sleep wake cycles crying when distressed Learning around 7 8 months o Fetuses recognize repeated familiar sounds o 37 weeks heart rate slowed attention when read to Individual differences o Differences in heart rate activity level o Children with higher heart rate variability in utero advanced Nature v Nurture OR BOTH language play o Temperament o Much of prenatal development is highly canalized however there are environmental influences on the developing organism
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