Transcript ch4.1
Chapter 4 Did you know…. 1. 2. 3. 4. 5. 6. “Identical twins” may not be exactly identical? All but 300 human genes have counterparts in mice? “Birth defects” do not always appear at birth? Fetuses can learn and remember while in the womb, and they respond to their mother’s voice? Drinking or smoking during pregnancy can do permanent damage to an unborn child? Prenatal care should begin before conception? Roles of Genetics Why do I have this hair color? Why do I have blue eyes like my mom instead of brown eyes like my dad? People inherit many physical traits from their parents. Traits can include skin color, hair texture and color, eye color, the size and shape of ears, and more. At the moment of conception, every human baby receives 46 chromosomes. Chromosomes are a tiny threadlike structure in the nucleus of every cell You get 23 from each parent Gene is a unit that determines a human’s inherited characteristics DNA is the complex molecules that make up your genes Your 46 chromosomes form your unique DNA No two people, except identical twins, have identical DNA What determines Sex? Autosomes: the 22 pairs of chromosomes not related to sexual expression Sex chromosomes: Pair of chromosomes that determines sex: XX in the normal female, XY in the normal male X chromosomes: chromosomes containing the genes for femaleness Y chromosomes: chromosomes containing the genes for maleness Wnt-4: a signaling molecule that appears to control the development of female characteristics Patterns of Genetic Transmission 1. Dominant inheritance: pattern of inheritance in which a child receives matching dominant alleles, or when a child receives contradictory alleles. In either case, the dominant characteristic is expressed. Recessive inheritance: pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a non-dominant trait Mutations: permanent alterations in genetic material that occur spontaneously or due to environmental hazards Chromosomal Abnormalities Defects Transmitted by Dominant or Recessive Inheritance Down syndrome: Chromosomal disorder characterized by moderate-to-serve mental retardation and by such physical signs as a downward-sloping skin fold at the inner corners of the eyes Trisomy 21: another name for Down syndrome, in which there is an extra of the21st chromosome or a translocation of part of the 21st chromosome onto another chromosome What Causes Multiple Births? Dizygotic (two-egg) twins: Twins conceived by the union of two different ova with two different sperm cells; Also called Fraternal twins Monozygotic (one-egg) twins: Twins resulting from the division of a single zygote after fertilization; also called Identical twins Temperament: Characteristic disposition or style of approaching and reacting to situations. Semi-identical-twins- the result of two sperm cells fusing with a single ovum. Conceiving New Life How Fertilization Takes Place Fertilization: Combining sperm and ovum to produce a zygote; also called conception Gametes: The sex cells, ovum and sperm Zygote: Single-celled organism resulting from fertilization Follicle: Small sac in the ovary containing the immature ova Ovulation: The rupture of a mature follicle and expulsion of the ovum. Cilia: Tiny hair cells in the fallopian tubes that sweep the ovum along Cervix: The opening of the uterus. Infertility Not all couples who want to become parents are able to have a child. Infertility is the inability to conceive a child. 40% of cases are due to female infertility 40% of cases are due to male infertility 20% have unknown causes or are linked to both partners Options for infertile couples Adoption Artificial insemination: dr. injects sperm into the woman’s uterus In Vitro Fertilization: dr. combines a mature ovum from the woman wht sperm from her husband. Pregnancy occurs if fertilized egg attaches itself to the uterus Ovum Transfer: similar to in-vitro, except an ovum from another woman is donated Surrogate Mother: A surrogate is a substitute. Where another woman becomes pregnant for the woman that can’t conceive. Legal arrangements are required. Prenatal Development The baby’s development during a pregnancy is called prenatal development Often grouped into 3 stages Germinal stage Embryonic stage Fetal stage Gestation: the approximately 9 month period of development between conception and birth Gestational age: Measurement of development from conception Germinal stage: Fertilization to 2 weeks 1. Germinal Stage (Fertilization to 2 weeks) Germinal stage: first two weeks of prenatal development, characterized by rapid cell division, and implantation in the wall of the uterus Cell Division: Mitosis: Period of rapid cell division and duplication Blastocyst: A Fluid-Filled sphere of cells that will float into the uterus and implant in the lining. Embryonic disk: A thickened cell mass located on the blastocyst, from which the embryo begins to develop Ectoderm: The upper layer of the embryonic disk that will form into the outer layer of skin, the nails, hair, teeth, sensory organs, and the nervous system . Implantation: the lining of the uterus has thickened enough for the zygote to attach. Despite the rapid growth the zygote is only the size of the head of a pin. Embryonic Stage (2 to 8 Weeks) Embryonic stage: second stage of gestation (2 to 8 weeks), characterized by rapid growth and development of major body systems and organs (developing baby is now called a fetus) Trimester: A 3-month period of pregnancy Organs and body systems: the cells begin to separate and develop into the major systems of the human body. Include the heart, lungs, bones, and muscles. About 27 days after conception, the neural tube has closed. The neural tube is a tube in the back of the developing baby that will become the brain and spinal cord Stages of Prenatal Development Endoderm: The lower layer of the embryonic disk that will form into the digestive system, liver, pancreas, salivary glands, and respiratory system Mesoderm: The inner layer of the embryonic disk that will form into the inner layer of skin, muscles, skeleton, and excretory and circulatory systems Placenta: Organ that provides oxygen and nourishment to the developing baby and removes it body wastes Umbilical cord: Cord that connect and vice versa Amniotic sac or Amniotic cavity: Fluid-filled membrane that encases the developing baby, protecting it and giving it room to move Amnion and chorion: Outer layers of amniotic sac Fetal Stage (8 weeks to Birth) Fetal stage: Final stage of gestation (from 8 weeks to birth), characterized by increased detail of body parts and greatly enlarged body size Ultrasound: Prenatal medical procedure using high-frequency sound waves to detect the outline of a fetus and its movements, to determine whether a pregnancy is progressing normally Making movement: sometime during 4th and 5th month, the kicks and other movements of the fetus touch the wall of the uterus. During this time parents talk, read, or sing to the developing fetus to encourage movement. Fetus: has all 5 senses, can cry, and sleeps 90% of the day. During the 8th month the baby settles into the proper position for delivery Fetal stage Growing Bigger: as the fetus grows so does the amniotic fluid and the uterus Ready for birth: the common length for pregnancy is about 40 weeks, or 280 days, from the first day of the last menstrual cycle. By the 9th month the fetus is fully developed and can usually survive outside of the womb. Environmental Influences: Maternal Factors Teratogenic: Capable of causing birth defects Transforming growth factor alpha: A variant of a growth gene, this factor causes a fetus to have six times more risk than other fetuses of developing a cleft palate if the mother smokes while pregnant. 1. Nutrition and Maternal weight 2. Malnutrition 3. Drug Intake A. Medical Drugs B. Alcohol Fetal alcohol syndrome (FAS): Combination of mental, motor, and developmental abnormalities affecting the offspring of some women who consume alcohol during pregnancy C. Nicotine D. Caffeine E. Marijuana, Cocaine, and Methamphetamine 4. Mental Illness Acquired immune deficiency syndrome (AIDS): Viral disease that undermines functioning of the immune system. Perinatal transmission: Virus may cross over to the fetus’s bloodstream through the placenta during pregnancy, labor, or delivery or, after birth, through breast milk Toxoplasmosis: An infection caused by a parasite harbored in the bodies of cattle, sheep, pigs, and in the intestinal tracts of cats. 5. Maternal Stress of Anxiety 6. Maternal Age 7. Outside Environmental Hazards Paternal Factors