5.3- Following Patterns of Inheritance in Humans SBI3U

What is a Pedigree? Flowchart; “Genetic Family Tree Symbols show inheritance patterns of traits over generations Used to determine presence/absence of an allele responsible for disease in an individual.

Pedigree Symbols

Roman numerals symbolize generations EXAMPLE: *NOTE: Roman numerals symbolize generations Birth order, within each group of offspring, is drawn left to right (first born to last born)

Autosomal Inheritance Inheritance of traits on chromosomes 1 -22(autosomes) Autosomal dominant: Disease causing allele is dominant Individual has one or both copies of the allele Autosomal recessive: Disease causing allele is recessive Individual has both copies of allele

Autosomal Dominant Inheritance Each affected individual has an affected parent; no skipping of generations. Males and females are equally affected. About 1/2 of the offspring of an affected individual are affected (the recurrence risk is 1/2). Normal siblings (ex. II-3) of affected individuals have all normal offspring.

Example- Pedigree: Autosomal Dominant Inheritance Question: Why must individual II-1 be heterozygous?

Autosomal Recessive Inheritance Two unaffected parents can have an affected child This only happens if both the parents are “carriers” Both are heterozygous (so they do not express it)

Example –Pedigree: Autosomal Recessive Inheritance Question: Are parents II 3 and 4 heterozygous or homozygous? Explain.

Examples of Human Diseases – Autosomal Inheritance 2)Huntington Disease 1)Sickle Cell Anemia Dominant Loss of muscle control and mental ability Recessive Irregularly shaped red blood cells 3) Cystic Fibrosis Recessive Mucus build up in lungs = trouble breathing

Let’s try this…Who can roll their tongue??? http://www.zerobio.com/drag_gr11/pedigree11_flash.htm

Genetic Tests

Genetic Counselling Genetic counsellors are trained in human genetics Work with families/individuals who may be at risk for a genetic disorder. Look at probability of passing on a disease-causing allele to children through family history using Pedigrees

What issues might be associated with genetic testing? Class Discussion: What issues might be associated with genetic testing?

Gene Therapy Technique used by introducing the correct form of a gene into a patient’s genome Goal? For curing genetic disorders!! METHOD-Normal gene is copied and inserted into vector (viruses are used bc they can easily infect human cells.

The Future of Gene Therapy… Still in the experimental stage 2 Problems/ Obstacles: 1)Problems with type of vector 2)Poor integration of gene into chromosomes In 2000, first human gene therapy treatment was performed for heart disease at St. Mike’s Hospital, Toronto

Homework Read and review 5.3-pg 219-226 Chapter 5 QUIZ T.B.A Complete pg. 227 # 2, 7, 8 Pedigree Assignment