Sexlinked Inheritance

1
Sex-linked Inheritance
2
Objectives

• Know the difference between autosomal chromosomes
  and sex chromosomes.
• Understand sex-linked inheritance.
• Be able to create a family pedigree.
• Solve sex-linked problems using a Punnett square

3
Gender Determinationin Humans

• Humans have 23 pairs of chromosomes.
• 22 of them are called autosomal.
• The 23rd pair are the sex chromosomes.
• XX Female
• XY Male

4
Pedigree
Marriage
XY
XX
Mother
Father
Children
XY
XY
XX
Son
Daughter
Son
Oldest
Youngest
5
Red/Green Colorblindness

• The gene which allows us to distinguish between
  red and green is on the X chromosome.

Female with normal vision
Female carrier
Female who is colorblind
6
Red/Green Colorblindness

• The gene which allows us to distinguish between
  red and green is on the X chromosome.

Male with normal vision
Male who is colorblind
7
Pedigree
Mother
Father
??
??
??
Son
Daughter
Son
8
Pedigree
XY
XX
c
C
C
Mother
Father
Son
Daughter
Son
9
Using a Punnett Square
XX
C
c
10
Genotype Phenotype
XX
C
c
Female Carrier
Female Colorblind
Male Normal
Male Colorblind
11
Hemophilia
XX
Female normal
H
H
XX
Female carrier
H
h
XX
Female with hemophilia
h
h
XY
Male normal
H
XY
Male with hemophilia
h
12
Review

• Autosomal??
• Pedigree - Male? Female? Marriage? Children?
  Siblings?
• Why do sex-linked traits affect males more
  frequently than females?

13
Homework

• Sex-linked Practice Problems