How can you study human heredity? HB p. 113 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 Typically, the occurrence of the trait is determined based on family/historical documents, interviews, photographs, & medical records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 With Trait Without Trait Female Male

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 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? Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Sex Linked! (in this case allele is recessive and located on the X chromosome) Brother You

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 Can get color blind from nerve damage, or drugs (one drug used to treat arthritis causes color blindness), but most of the time is a genetic disorder. Color blindness is a life long condition, doesn’t impact day to day life that much. Color blind people may not be able to do certain jobs that require seeing color, like a fashion designer or a cook who needs to be able to tell when the meat is done, or an electrician who can’t tell the difference between wire colors that she or he needs to cut

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 Hemoglobin carries oxygen to cells, life expectancy shorter, patients used to die of organ failure between 20 and 40, but now people tend to live into their 50s in the US anyway

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 To help, medications are often given for mucus buildup and have to keep a strict diet to help with digestion problems

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 People born with hemophilia have little or no clotting factor. Clotting factor is a protein needed for normal blood clotting. There are several types of clotting factors. These proteins work with platelets to help the blood clot.

Huntington’s Disease Autosomal, dominant 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 15-20 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! In a pedigree, what shape represents a male? What are lines used to indicate in a pedigree? What do pedigrees tell us about the inheritance of a trait in a family?