Mark the Genotype
Download
Report
Transcript Mark the Genotype
PEDIGREES
Analyzing family relationships for genetic clues
Pedigree diagram
A pedigree is a diagram of the individuals and
their relationships in a family group.
People are represented by symbols.
Lines show the connections between people.
Purpose:
To
determine the mode inheritance of a genetic
disease.
To estimate the risk of passing on a genetic disease.
Symbols
Males are square.
Females are round.
Affected individuals are
dark.
Normal or unknown are
white.
Horizontal lines are
matings. Parents
Vertical lines are
between generations
Who is who?
The oldest generation is at
the top of the diagram.
Newest generation is at
the bottom.
Generations are counted
from the oldest generation
using Roman numerals.
Count top to bottom
Individuals can be
numbered.
Left to right
Three Types of Inheritance
Each type has a distinctive
pattern
Autosomal Dominant
Autosomal Recessive
Sex-Linked Recessive
Autosomal Dominant
Present in each
generation. No
skipping.
Males and Females
are equally likely to
be affected.
Each affected person
has an affected
parent.
Unaffected person
has unaffected
offspring. WHY?
Autosomal Recessive
Must be
homozygous to be
expressed.
If child is rr, then
the parents must be
_____.
Recessive can skip
generations.
Sex-Linked Recessive
Recessive may skip
generations.
Males have one X, and
males are more likely to
be affected.
Never passes from
father to son.
An affected male gets
his X from his mom, II-2.
What is her genotype?
X Xc or
Xc Xc
Test the pedigree for a pattern
Mark the genotypes.
Try the three patterns.
What pattern is possible?
Use these letters for Sex Linked only.
XA = normal
Xa = the trait (a genetic disease or abnormality)
Y = Y chromosome (males only)
Autosomal Dominant
Autosomal Recessive
Sex-Linked Recessive
What is the pattern?
Mark the genotypes.
Try the three patterns.
What patterns are possible?
Use these letters for Sex Linked only.
XA = normal
Xa = the trait (a genetic disease or abnormality)
Y = Y chromosome (males only)
Autosomal Dominant
Autosomal Recessive
Sex-Linked Recessive
What is the pattern?
Mark the genotypes.
Try the three patterns.
What pattern is possible?
Use these letters for Sex Linked only.
XA = normal
Xa = the trait (a genetic disease or abnormality)
Y = Y chromosome (males only)
Autosomal Dominant
Autosomal Recessive
Sex-Linked Recessive
Create a Pedigree
Put the male parent to the left of the female. (I generation)
Draw a horizontal line between parents.
Draw a line down from the parents to a horizontal line
connecting a group of brothers and sisters.
(II generation)
Siblings are entered with the oldest to the left and youngest
is to the right.
Draw a line across between a sibling and their spouse. Draw
down from this line to their children (grandchildren of I
generation).
(III generation)
Darken all individuals who are affected.
Mark carriers with a half dark/half light symbol.
Check your understanding
What can you conclude about the parents of a person
that has a dominant characteristic? (Check the correct
answer below.)
--If a person has a dominant trait, the parents will not
have the trait.
--If a person has a dominant trait, the parents might
have the trait or they might not have it.
--If a person has a dominant trait, at least one of the
parents will have the trait.
--If a person has a dominant trait, both of the parents
will have the trait.
Test an Autosomal Dominant
Can two individuals that have an
autosomal dominant trait have
unaffected children? (Check the correct
answer below.)
--If two individuals have a dominant
trait, none of their offspring will have
the trait.
--If two individuals have a dominant
trait, their offspring might or might not
have the trait.
--If two individuals have a dominant
trait, their offspring will have the trait.
Mark the Genotype
What is the pattern?
Label the generations.
Number the people.
Mark the genotypes.
Dominant/Recessive?
Autosomal/Sex-linked?
What is the pattern?
___________________
Dominant or Recessive?
Autosomal or Sex-linked?
What is the pattern? _______________
Trace the lines between IV-4 to the oldest person
with the trait.
Dominant or Recessive?
Autosomal or Sex-linked?
What is the pattern? _______________
Label genotypes. Start with the affected
individuals.
Dominant or Recessive?
Autosomal or Sex-linked?
What is the pattern? _______________
Which person is the best clue? __________
Resources
McClean, Phillip, 2000, Mendelian Genetics, North
Dakota State University,
http://www.ndsu.edu/pubweb/~mcclean/plsc431/
mendel/mendel9.htm
Tissot, Robert, 2014, Human Genetics, University of
Illinois Chicago,
http://www.uic.edu/classes/bms/bms655/lesson3.h
tml#Sample