Pedigrees Woof

The Royal Hemophiliacs Last class we brought up hemophilia, a disease where the blood doesn’t clot normally A famous case occurred in the Royal family

How can we trace the inheritance and predict who will be affected?

Another example: Race Horses Horse Racing is HUGE industry with lots of money at stake Owners want to invest in a horse that will win. They will pay big money to get a horse born from a ‘winning’ dam and sire. How can you follow the mating of several horses to determine which horses will make a prize-winning foal?

A Pedigree is a chart that traces the inheritance of a trait amongst members of a family It shows ancestry, and is often used to look at the inheritance of a particular trait, often a disease It is used to breed plants and animals to optimize ‘good traits’ and lose ‘bad’ traits

The Basics of a Pedigree Each person is represented by a symbol Birth order is from left to right (oldest  youngest)

How are we related? I 12 II III

4 Main types of Inheritance Autosomal Dominant Autosomal Recessive Sex-Linked Dominant Sex Linked Recessive Also, holandric (Y-linked), and diseases can be sporadic (not genetic) But how can we use a pedigree to figure out inheritance?

How can we use a pedigree to understand inheritance Use our knowledge of genetics and Punnett Squares i.e What is the genotype of II-1 if he expresses an autosomal recessive disorder for the gene ‘r’? What are his parents genotypes? What possible genotypes does his sister have?

If I-2 is a carrier for male pattern baldness, what do we expect to be the phenotype of her children?

Determining Genotype What are the genotypes of all the individuals listed if the mutation for colourblindness is inherited in a sex- linked recessive manner? XbYXbY XbYXbY XBXBXBXB XBXbXBXb XBYXBYXBYXBY XBYXBY XBYXBY

Patterns of Inheritance

Autosomal Dominant Affected individuals have one affected allele and one normal allele Each offspring has a 50% chance of inheriting the mutant gene

Autosomal Recessive Affected only when have TWO copies of the mutant gene 1 mutant copy/1 normal = carrier Females and males are equally affected

Autosomal Recessive When 2 carriers mate: 25% homozygous unaffected, 50% carriers, 25% affected

X-Linked Recessive All females who have it are carriers but look normal All males who have it are affected No father to son transmission but if a father is affected, his daughter will be a carrier

X-linked Dominant No father to son transmission All of an affected man’s daughters will be affected 50% of an affected woman’s children will be affected

What mode of inheritance? Autosomal Dominant!

Assemble and interpret the pedigrees Each table group is given a sheet that outlines some of the individuals in a family Draw a proper pedigree on chart paper Determine the mode of inheritance Determine the phenotype/genotype of several individuals

Your Pedigree must have: Generation numbers Individual numbers Affected/Deceased/Carriers are marked For this example, I also want you to include the genotype of each person once you figure out the mode of inheritance