Human Heredity  This section explains what scientists know about human chromosomes, as well as the inheritance of certain human traits and disorders.  It also describes how scientists study the inheritance of human traits.

Human Chromosome  How do biologists make a karyotype?  A karyotype is simply a picture of a person's chromosomes in mitosis.  The chromosomes are isolated in the WBC, stained, and examined under the microscope.  A picture of the chromosomes is taken through the microscope.  They cut out the chromosomes from the photographs, then group them together in pairs.

Make A Karyotype  Virtual lab:  osomes/karyotype/ osomes/karyotype/ Other Virtual Lab: ryotyping.html

The Punnett square below shows how the sex chromosomes segregate during meiosis.

Pedigree definition  Pedigree: a family history that shows how a trait is inherited over several generations  Pedigrees are usually used when parents want to know if they are carriers of a particular disorder

Making a Pedigree  Female  Male  Married Couple  Siblings Filled in symbols indicate individual is affected with a disorder

Example of a Pedigree You Parents Aunts, Uncles Grandparents Brother Do any disorders run in this family??

Interpreting a Pedigree  What can you tell from a pedigree?  Whether a family has an autosomal or sex-linked disease or disorder  Autosomal disorder: appears in both sexes equally  Sex-linked disorder: allele is located only on the X or Y chromosome. Most sex-linked genes are on the X chromosome and are recessive  So who would have an X-linked disorder more often, boys or girls?  Whether a disorder is dominant or recessive

Is this disorder 1) autosomal or sex linked, 2) dominant or recessive? You Parents Aunts, Uncles Grandparents Brother Sex Linked! (in this case allele is recessive and located on the X chromosome)

Is this disorder 1) autosomal or sex linked, 2) dominant or recessive? You Parents Aunts, Uncles Grandparents Brother Autosomal dominant!

Is this disorder 1) autosomal or sex linked, 2) dominant or recessive? You Parents Aunts, Uncles Grandparents Brother Autosomal recessive!

Common Genetic Disorders  Color blindness  Sickle cell anemia  Cystic Fibrosis  Hemophilia  Huntington’s Disease For more info, go to:

Color Blindness  Deficiency to percieve colors  Problem with color- sensing pigments in certain nerve cells of the eye  About 1 in 10 men have some form of color blindness.  Sex-linked disorder

Sickle Cell Anemia  Disorder where abnormal hemoglobin (a protein inside red blood cells) is produced and warps red blood cells  Sickle cells deliver less oxygen to body’s tissues and can get stuck in small blood vessels  Recessive trait, tends to be seen in people of African or Mediterranean descent

Cystic Fibrosis  Recessive, autosomal disease  Life threatening, causes thick mucus to build up in various areas of the body (lungs, digestive tract, etc).  Tends to run in Caucasians, of Northern/Central European descent (1 in 29 Americans carry the allele)  Average life span in US for people with CF is 37, death usually caused by lung complications

Hemophilia  Bleeding disorder, where it takes a long time for blood to clot (body lacks proteins involved in clotting)  Sex-linked (carried on the X chromosome)  Treatment involves injection with missing clotting protein

Huntington’s Disease  Autosomal, dominant  Deterioration of brain tissue, usually begins between age 30 and 40.  No cure, but have medications to cope with symptoms  People usually die years after onset of degeneration