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Human Heredity How can you study human heredity? Studying human heredity Population sampling determines how often a trait appears in a small, randomly selected group. This percentage is then applied to the entire population to predict the number of individuals with that trait. Studying human heredity Pedigrees graphically record inheritance of a single trait over several generations. Typically, the occurrence of the trait is determined based on family/historical documents, interviews, photographs, & medical records Pedigrees Specific shapes are used to represent individuals in a pedigree Individual Female Male With Trait Without Trait Pedigrees Connecting lines are used to indicate relationships among individuals within the family P1 parental F1 first filial F2 Second filial Fill It In … Draw a pedigree that shows a mom and dad that have two girls, one boy. The boy is married. Indicate that all the males have the trait. Pedigrees Pedigrees demonstrate the pattern of inheritance (dominant/recessive , sex-linked) of the single trait. Pedigrees Pedigrees can be interpreted to determine the presence of carriers (individuals who do not express the trait but may pass the gene on to offspring) Pedigrees Example: The two parents (P1 generation) must have been carriers (Bb) for a recessive trait. Neither showed the trait, but they had a child with the trait (bb). Fill It In … Signs a pedigree shows a trait that is … Recessive Sex-linked - Interpreting a Pedigree What can you tell from a pedigree? Whether a family has an autosomal or sexlinked 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? Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Brother You 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? Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Autosomal dominant! Brother You Practice Pedigree Type O blood is recessive to Type A and B blood. Tom had type B blood and married Shana, who had type A blood. Together, they had 2 children: Cherith (type O) and Bryan (type AB). Bryan married Ali (type O) and they had two children: Christian (type A) and Jon (who could not donate blood to Christian). Ali had an affair with Trent, who was homozygous for blood type A. Ali and Trent had a child with type A blood. Common Genetic Disorders Color blindness Sickle cell anemia Cystic Fibrosis Hemophilia Huntington’s Disease For more info, go to: http://www.ncbi.nlm.nih.gov/pubmedhealth/ 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 •Describe the trait or disease you chose 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 1520 years after onset of degeneration •Describe the trait or disease you chose Some History Hemophilia has played an important role in Europe's history The disease began to crop up in Great Britain's Queen Victoria’s children It became known as the "Royal disease" because it spread to the royal families of Europe through Victoria's descendants How it Spread it spread through the Royal Houses of Europe as monarchs arranged marriages to consolidate political alliances. We can trace the appearance of hemophilia as it popped up in Spain, Russia, and Prussia by looking at the family tree. The Royal Family Tree Queen Victoria's son Leopold's Family His daughter, Alice of Athlone, had one hemophilic son (Rupert) and two other children - a boy and a girl -whose status is unknown. What is the chance that her other son was hemophilic? What is the probability that her daughter was a carrier? hemophiliac? German and Russian Influences Check Yourself! 1. In a pedigree, what shape represents a male? 2. What are lines used to indicate in a pedigree? 3. What do pedigrees tell us about the inheritance of a trait in a family? Check Yourself! 1. In a pedigree, what shape represents a male? SQUARE 2. What are lines used to indicate in a pedigree? 3. What do pedigrees tell us about the inheritance of a trait in a family? Check Yourself! 1. In a pedigree, what shape represents a male? SQUARE 2. What are lines used to indicate in a pedigree? RELATIONSHIPS AMONG INDIVIDUALS 3. What do pedigrees tell us about the inheritance of a trait in a family? Check Yourself! 1. In a pedigree, what shape represents a male? SQUARE 2. What are lines used to indicate in a pedigree? RELATIONSHIPS AMONG INDIVIDUALS 3. What do pedigrees tell us about the inheritance of a trait in a family? PATTERNS OF INHERITANCE (DOMINANT/RECESSIVE OR SEX-LINKED) PRESENCE OF CARRIERS