PedigreesWoof Woof

The Royal HemophiliacsLast 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 followthe mating of several horses to determinewhich 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 usedto look at the inheritance of a particulartrait, often a disease

It is used to breed plants and animalsto optimize ‘good traits’ and lose ‘bad’traits

The Basics of a PedigreeEach person is represented by a symbol

Birth order is from left to right (oldest youngest)

How are we related?

I 1 2

II 1 2 3 4 5 6 7 8

III 1 2 3 4 5 6 7 8 9

4 Main types of InheritanceAutosomal 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

inheritanceUse our knowledge of genetics and Punnett

Squares

i.e What is the genotype of II-1if he expresses an autosomalrecessive disorder for the gene‘r’?

What are his parents genotypes?

What possible genotypes doeshis sister have?

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

Determining GenotypeWhat are the genotypes of all the individuals

listed if the mutation for colourblindness is inherited in a sex-linked recessive manner?

XbY

XbY

XBXB

XBXb

XBY XBY XBY

XBY

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