Download Analyzing Pedigree Charts (Pgs. 299-310)

Analyzing Pedigree Charts (Pgs. 299-310)
1.
Describe in your own words what a pedigree is and how it is used in genetics.
2.
In your own words, explain the following symbols used in a pedigree:
a. Square
b.
Circle
c.
Dark, filled shape
d.
Unfilled shape
e.
Half shaded shape
f.
Horizontal line
g.
Vertical line
h.
Roman numerals
i.
Arabic (regular) numerals
Analyzing pedigree charts
The first thing you need to analyze on a pedigree chart is if the trait being studied is dominant or recessive. Here are some
clues to help:
 Recessive
 Individual expressing trait has 2 normal parents
 Two affected parents cannot have an unaffected child or two unaffected parents can have an affected child
 Very common for it to skip a generation
 Dominant
 Every affected person has at least one affected parent or unaffected parents cannot have an affected child
 Each generation tends to have affected individuals
3.
Is the trait on the pedigree chart shown above dominant or recessive?
a. How do you know?
4.
Is the trait on the pedigree chart shown above dominant or recessive?
a.
How do you know?
_____________________________________________________________________________________________________
5.
What does it mean if a trait is considered sex or x-linked?
6.
What does it mean if a trait is considered autosomal (hint: it is opposite from your answer to #6)?
7.
Explain in your own words how you can tell if a trait being studied on a pedigree chart is autosomal or sex-linked
(hint: think of which gender has a greater chance of being color blind).
_____________________________________________________________________________________________________
8.
Is the trait on the pedigree chart shown above autosomal or sex-linked?
a.
9.
How do you know?
Is the trait on the pedigree chart shown above dominant or recessive?
a.
How do you know?
10. Is the trait on the pedigree chart shown above autosomal or sex-linked?
a.
How do you know?
11. Is the trait on the pedigree chart shown above dominant or recessive?
a.
How do you know?
The ability to roll your tongue is dominant (R) to not being able to roll your tongue (r). Below is the Snow family history of
this trait.
Grandpa Snow is a tongue roller but Grandma Snow is not. They have four children (2 sons and 2 daughters) who are all
rollers. Their last daughter, Judy, married John Flake. John’s parents are both rollers, but John’s two sisters are non-rollers.
John is a roller. John and Judy Snow-Flake have three children named Crystal Snow-Flake (a non-roller), Pretty Snow-Flake (a
roller) and Jake Snow-Flake (a roller).
12. Using the proper symbols, lines and numbers, draw a pedigree to show the inheritance of this trait.
13. Write down the genotype of each individual shown on your pedigree: RR or Rr or unknown.