Memmler’s A&P Chap 25 Heredity and hereditary disease
Heredity p526 Genes When somatic cells divide by mitosis, DNA is replicated so that each new cell has the full set of DNA from the original cell. Somatic cells have 23 pairs of chromosomes
Dominant and Recessive genes p526 A dominant gene: expresses its effect in the cell regardless of whether its allele on the matching chromosome is the same as or different from the dominant gene. A recessive gene: is not expressed unless it’s paired allele on the matching chromosome is also recessive
Distribution of chromosomes to offspring p527 Meiosis divides the chromosome number in half, so that each reproductive cell has 23 chromosomes. At fertilization, the chromosomes in the sperm and egg combine to make the usual 23 pair of chromosomes
Determination of eye color p527 B=brown eyes b=blue eyes
Sex determination p527 Sperm determines the sex of a child X from mama + X from daddy = girl baby X from mama + Y from daddy = boy baby
Hereditary traits p528 Observable hereditary traits: – Skin, eye, hair color – Facial features – Body build Less clearly defined traits: – Weight – Life span – Susceptibility to disease
Genetic mutation p528 Genetic mutation happens when chromosomes break, or rearrange cell fragments during meiosis or mitosis If the mutation occurs in an egg or sperm cell, the mutation will be inherited by the offspring
Congenital versus hereditary p529 Congenital means present at birth – Birth defect Hereditary means genetically transmitted – Hereditary conditions are frequently known at birth or soon thereafter, but some hereditary conditions are not evident until later
Causes of congenital disorders p530 German measles Ionizing radiation Toxins Alcohol (fetal alcohol syndrome) Cigarette smoking
Spina bifida p530
Chromosomes p534
Examples of genetic diseases p531 Trisomy 21 (Down syndrome) Sickle cell disease Cystic fibrosis
Prevention/detection of genetic diseases p533 Genetic counseling is best way to prevent genetic disease Lab studies Amniocentesis