Honors Biology Genetics!

Pedigree is a family tree used to study how particular human traits are inherited.

It is analyzed using logic and the Mendelian laws

1. Determine the mode of inheritance: dominant, or recessive, sex-linked or autosomal

2. Determine the probability of an affected offspring for a given cross.

1. If two affected people have an unaffected child.

2. If every affected person has an affected parent.

1. All unaffected are dd. 2. Affected children of an affected parent

and an unaffected parent must be heterozygous Dd, because they inherited a d allele from the unaffected parent.

3. The affected parents of an unaffected child must be heterozygotes Dd, since they both passed a d allele to their child. (also called carriers)

1 2 3 4 5 6 7 8 9 10

1 2

I

1 2 3 4 5 6

II

III

1. If two unaffected people have an affected child

1. all affected are rr. 2. If an affected person (rr) mates with an

unaffected person, any unaffected offspring must be Rr heterozygotes, because they got a r allele from their affected parent.

3. If two unaffected mate and have an affected child, both parents must be Rr heterozygotes.

Look for: Trait in every generation

Once leaves the pedigree does not return Every person with the trait must have a

parent with the trait Males and females equally affected

http://www.bioedonline.org/slides/slide01.cfm?q=pedigree&pg=1

Look for: Skips in generation Unaffected parents can have

affected children Affected person must be

homozygous Males and females affected equally

http://www.bioedonline.org/slides/slide01.cfm?q=pedigree&pg=1

Look for: More males being affected Affected males passing onto all

daughter (dominant) and none of his sons

Every affected person must have an affected parent

Look for: More males being affected Affected female will pass onto all her

sons Affected male will pass to daughters

who will be a carrier (unless mother also affected)

Unaffected father and carrier mother can produce affected sons

http://www.bioedonline.org/slides/slide01.cfm?q=pedigree&pg=3