Download Pedigree Notes

Pedigree
Notes
What is a pedigree?
• A pedigree is a diagram of family
relationships that uses symbols to
represent people and lines to represent
genetic relationships.
• Pedigrees are often used to determine the
mode of inheritance (dominant, recessive,
etc.) of traits and genetic diseases.
Rules for Pedigrees
1.
Squares represent males
and circles represent
females
2.
Horizontal lines connecting
a male and female
represent mating
3.
Vertical lines extending
downward from a couple
represent their children
4. Oldest individuals are found at the top of the
pedigree
5. Shade in the symbol of all individuals that
possess this trait
6. If an individual died due to the trait, put a slash
through their symbol
Lethal Allele
• Dominant example:
• Alleles that cause
Huntington’s
an organism to die
only when present • Recessive
in homozygous
example: Cystic
condition are called
Fibrosis
lethal alleles.
• The gene involved
is considered an
essential gene.
Developing
Conclusions About
Different Modes of
Inheritance
Autosomal Dominant
tt
Tt
Tt
• Shaded individuals HAVE the
trait and must have the
dominant allele (at least one
capital letter).
tt
•Un-shaded individuals do NOT
have the trait. They are
homozygous recessive (two
lower case letters).
•The traits are often present in
every generation.
Autosomal Recessive
Tt
tt
Tt
T?
• Shaded individuals HAVE the
trait and they are homozygous
recessive (two lower case letters).
•Un-shaded individuals do NOT
have the trait and must have the
dominant allele (at least one
capital letter).
•The traits are often present in
every other generation
Practice #1
Is the pedigree for a dominant or recessive trait?
Give the genotypes for each individual.
Practice #2
Is the pedigree for a dominant or recessive trait?
Give the genotypes for each individual