Generation to Generation • Chromosomes:Tiny structures with in the nuclei of cells that carry information about heredity traits. • ~Cells in the body contain 46 chromosomes: 23 pairs. • ~At the foundation of chromosomes is the chemical compound- DNA. • ~Specific information about heredity are carried w/in sections of chromosomes called Genes. • Genes: Segments of DNA molecules are paired. • Dominant Genes:genes that generally show up in the offspring whenever they are present. • Recessive Genes:Usually show up only when dominant genes are not present. • (Example: Blue eyes are recessive, Brown eyes are dominant. If mom has blue eyes, and dad has brown eyes, most likely the child will have brown eyes.)
Genes & Gender ~A zygote has 46 chromosomes- 23 each parent. ~Males have xy, y is the shorter chromosome. ~Female has xx, both are the same. ~Ova and sperm have only 1 chromosome ~Ova have only x ~Sperm have x or y *The sex of the child is determined by the type of sperm that finds the egg(Ova).
Genetic Disorders • Sickle Cell Anemia:Disease occurs when a child inherits the hemoglobin (Oxygen-carrying part of blood) gene from both parents. The red blood cells develop a sickle shape and clump together obstructing blood flow and oxygen to the tissues. • ~Symptoms- severe joint and abdominal pain, weakness & kidney disease. • Phenylketonuria: A protein called phenylalanine accumulates in the body, interfering with the development of brain cells causing mental retardation. If caught early, diet & treatment can be given. • Tay-Sachs Disease:Causes destruction of nervous system, blindness, and death during early childhood.
Genetic disorders continued… • Cystic Fibrosis:Makes breathing and digestion difficult, its caused by abnormal genes, one from each parent. • Down Syndrome:Caused by a chromosomal abnormality known as Trisony-21,( the presence of three copies of the 21st chromosome). As a result, the affected person has an extra 47th chromosome in all body cells.
Identifying Disorders • Amniocentesis:A syringe is inserted through the pregnant woman’s abdominal wall into the amniotic fluid surrounding the developing fetus. • ~Performed 16-20 weeks after fertilization. • Ultrasound:Sound waves are used to project light images on a screen. This determines if fetus is in the correct position and how many fetus are in uterus. • Chorionic Villi Sampling: A small piece of membrane is removed from the Chorion ( a layer of tissue that develops into the placenta). Takes place around the 8th week of fertilization. • ~This is done earlier then amniocentesis.