7.2.d Students know plant and animal cells contain many thousands of different genes and typically have two copies of every gene. The two copies (or alleles) of the gene may or may not be identical, and one may be dominant in determining the phenotype while the other is recessive.

 Genetic disorder- an abnormal condition that a person inherits through genes or chromosomes  Key concept : “Some genetic disorders are caused by changes in the DNA of genes. Other disorders are caused by changes in the overall structure or number of chromosomes.”

CYSTIC FIBROSIS SICKLE-CELL DISEASE  caused by a recessive allele as a result of a mutation  body produces abnormally thick mucus in the lungs and intestines  makes it hard to breathe  codominant with normal cells  person with two sickle-cell alleles has the disease  person with one sickle-cell allele has both normal and abnormal hemoglobin  unusual shaped blood cells that clogs the blood vessels

HEMOPHILIADOWN SYNDROME  Caused by a recessive allele on the X chromosome  Sex-linked  Blood cots very slowly or not at all  Person doesn’t produce one of the proteins needed for clotting  Extra copy of chromosome 21  Most often happens when a chromosome fails to separate during meiosis

This pedigree shows the inheritance of hemophilia in a family. Pedigree- a chart that tracks members of a family with a particular trait Key Concept: “One important tool that geneticists use to trace the inheritance of traits in humans is a pedigree.” Pedigrees can be about normal traits like widow’s peak or genetic disorders

 Key Concept: “Today, doctors use tools such as karyotypes to help diagnose genetic disorders. People with genetic disorders are helped through medical care, education, job training, and other methods.”  Doctor’s use Punnett squares and pedigrees to help predict whether a child might have a genetic disorder or not  Karyotype- a picture of all the chromosomes in a cell showing if a person has the correct number of chromosomes or not

Genetic counseling  Families that have a history of a genetic disorder  Help people understand the chances of having a child with a specific disorder  Use Punnett squares, pedigrees, karyotypes to help Karyotyping Punnett square Pedigree

Dealing with Genetic Disorders Deal with serious challenges Modify environment Medicine, diet, and vitamins Education People can still live active and productive lives

 A pedigree is a chart or “family tree” that tracks which members of a family have a particular trait.

What are two major causes of genetic disorders in humans? How do geneticists trace the inheritance of traits? How are genetic disorder diagnosed and treated?