Learning Objectives Unit Two Chapter Three 1 Define genotype and phenotype and describe the differences between them What are genes and how are they transmitted between generations through mitosis and meiosis Genotype the complex blend of genetic information that determines our species and influences all our unique characteristics Phenotype directly observable characteristics Genes segment of DNA along the length of the chromosome A unique feature of DNA is that it can duplicate itself through a process called mitosis As a result each new body cell contains the same number of chromosomes and the identical genetic information A wide range of environmental factors modify gene expression So even at this microscopic level biological events are the result of both genetic and nongenetic forces Meiosis gametes are formed through this cell division process which halves the number of chromosomes normally present in body cells 2 What determines the sex of a child What are gametes and zygotes Sex chromosomes XX XY determines the sex The sex of a new organism is determined by whether an X bearing or a Y bearing sperm fertilizes the ovum Gametes new individuals are created when two special cells sex cells the sperm and ovum combine Contains only 23 chromosomes half as many as a regular body cell Created through meiosis Zygotes Gametes are formed through meiosis which halves the number of chromosomes normally present in body cells When sperm and ovum unite at fertilization the resulting cell a zygote will again have 46 chromosomes 3 What are the two types of twins and how are they created Identical monozygotic twins sometimes a zygote that has started to duplicate separates into two clusters of cells that develop into two individuals They have the same genetic makeup Fraternal dizygotic twins the most common type of multiple birth result from the release and fertilization of two ova Genetically they are no more alike than ordinary siblings Older maternal age fertility drugs and in vitro fertilization are causes of this 4 Describe basic patterns of genetic inheritance including examples of each type and implications of inheritance e g homozygous dominant heterozygous dominant homozygous recessive Dominant recessive inheritance only one allele affects the child s characteristics Hair color is an example Dark hair is dominant and blond hair is recessive PKU example Homozygous dominant both alleles are the same and dominant Child will receive both alleles Incomplete dominance a pattern of inheritance in which both alleles are expressed in the phenotype resulting in a combined trait or one that is intermediate between the two The sickle cell anemia occurs in full form when a child inherits two recessive alleles They cause the usually round red blood cells to become sickle shaped which clogs the blood vessels and block the flow of blood 5 Describe conception and the three periods of prenatal development What are the milestones of each period Conception Each sperm develops a tail that permits it to swim long distances upstream in the female reproductive tract through the cervix opening of the uterus and into the fallopian tube where fertilization usually takes place Only 300 to 500 reach the ovum Most conceptions result from intercourse during a 3 day period on the day of ovulation or during the 2 days preceding it SPERM AND OVUM UNITE TO FORM THE NEW INDIVIDUAL 1 Period of the zygote cells that become the new organism and cells that become the structures that provide protective covering and nourishment 2 Period of the embryo most rapid prenatal changes take place as the groundwork is laid for all body structures and internal organs 3 Period of the fetus during this growth and finishing phase the organism increases rapidly in size especially from the ninth to the twentieth week longest prenatal period 6 What are teratogens What factors affect how teratogens impact prenatal development Give examples of known teratogens and describe how it is difficult to determine how environmental agents impact prenatal development Teratogens refers to any environmental agent that causes damage during the prenatal period Dose heredity presence of several negative factors additional teratogens poor nutrition and lack of medical care can worsen the impact of a single harmful agent and age effects vary with the age of the organism at time of exposure Known teratogens prescription and nonprescription drugs illegal drugs tobacco alcohol radiation environmental pollution maternal disease viruses bacterial and parasitic diseases The effects of teratogens go beyond immediate physical damage some health outcomes are delayed and may not show up for decades Psychological consequences may occur indirectly as a result of physical damage For example a defect resulting from drugs the mother took during pregnancy can affect others reactions to the child as well as the child s ability to explore the environment Over time parent child interaction and opportunities to explore may suffer and may be less resilient in the face of environmental risks 7 Name and describe how other maternal factors impact development What are the complications of maternal obesity Maternal exercise nutrition and emotional well being effect the embryo and fetus Also wonder how a mother s age affects the course of pregnancy Moderate exercise is related in reduction in risk for certain complications Emotional stress is associated with higher rates of miscarriage prematurity low birth weight Maternal obesity causes a greater loss in brain weight can distort the structure of other organs including the liver and kidneys Prenatally malnourished babies frequently catch respiratory illnesses They often are irritable and unresponsive to stimulation 8 What are the three stages of childbirth 1 Dilation and effacement of the cervix forms a clear channel from uterus into the birth canal or vagina longest stage lasting 12 to 14 2 Delivery of the baby with each contraction mom forces the baby hours down and out 3 Birth of the placenta placenta separates from the wall of the uterus and be delivered in about 5 to 10 minutes 9 What are the purposes and features of the Apgar scale What does the scale imply The apgar scale assesses the baby s physical condition used by doctors and nurses Infants who have difficulty making the transition to life outside the uterus A rating of 0 1 2 on each of five characteristics heart rate respiratory effort is made at 1 minute and again at
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