A Closer Look at Conception Section 5-2 The Developing Child

The Genetic Package 46 chromosomes Dominant = stronger gene 23 pairs Dominant = stronger gene Recessive = weaker gene A person receives two copies of a gene-one from the mother and one from the father

The Genetic Package The father’s sperm and the mother’s ovum both contribute a chromosome to each pair. When both are the same, the child has that characteristic (two genes for blue eyes give the child blue eyes).

Sex Chromosome Every ovum contains an X chromosome. Each sperm cell contains either an X or Y chromosome. If sperm carries X…results in an XX combination…becomes a girl. If sperm carries Y…results in XY combination…becomes a boy.

Multiple Births Identical Twins When a fertilized egg starts growing, it divides into two cells…these cells continue to divide. Sometimes the mass of cells splits in half soon after fertilization…results in identical twins Always the same sex and have very similar characteristics because both began as one zygote

Multiple Births Fraternal Twins 2 eggs are released from the ovary and both are fertilized by different sperm No more alike than siblings born at different times

Infertility Adoption: The couple legally takes all responsibilities and rights for raising a child already born

Infertility Artificial Insemination A doctor injects sperm into a woman’s uterus with a special needle The sperm may be the husband’s. If he has a history of genetic disorders or is unable to produce sperm…the sperm may come from another male…called a donor

Infertility In vitro fertilization When the woman has damaged fallopian tubes that prevent pregnancy. In a small glass dish, a doctor combines a mature egg from the woman and sperm from her husband or donor. If fertilization takes place, the doctor places the zygote in the woman’s uterus. If the zygote attaches to the uterine wall, normal pregnancy takes place.

Infertility Ovum Transfer May be used by women who lack working ovaries or who have inherited disorders. The procedure uses an egg taken from a female donor combined with in vitro fertilization.

Infertility Surrogate Mother This occurs when another woman becomes pregnant for another couple. Artificial insemination, in vitro fertilization, and/or ovum transfer may be used. When the woman gives birth, she gives the baby to the couple. Legal arrangements are made and they must meet state laws.

Problems in Prenatal Development Losing a baby…can cause a great deal of pain…usually happens naturally Miscarriage When the developing baby dies between 1-20 weeks of pregnancy Stillbirth When the developing baby dies after 20 weeks of pregnancy

Causes of Birth Defects Hereditary Causes Genes may be imperfect (dominant or recessive) Environmental Causes Nutritional balance of pregnant woman Diseases or infections during pregnancy Harmful substances during pregnancy Alcohol Tobacco Drugs Some medications can hurt the baby Exposure to outside hazards…radiation

Examples of Birth Defects Cerebral Palsy Cleft Lip/Palate Cystic Fibrosis Down Syndrome Muscular Dystrophy Sickle Cell Anemia Spina Bifida or Hydrocephalus Tay Sachs Disease

Prenatal Tests Ultrasound Uses sound waves to make a video image of an unborn baby to check for specific health problems It can show whether the fetus is developing on schedule Can confirm: due date, multiples, gender

Prenatal Tests Amniocentesis The process of withdrawing a sample of the amniotic fluid surrounding an unborn baby Can test the amniotic fluid for indications of specific birth defects or other health problems Risk: 1 in every 200 can result in miscarriage…only performed when there is a strong medical reason

Prenatal Tests Chronic Villi Sampling Used to test for specific birth defects Can be done earlier than an amniocentesis Guided by an ultra sound image, a doctor inserts a small tube through the vagina into the uterus…then samples of the tissue are snipped or suctioned off for analysis.

3-D Ultrasound compared to traditional Ultrasound