Sex-linked traits Sex-linked genes found on X chromosome males have one X & Y – genes on X will be
shown in males, even if recessive.
Y chromosome
X chromosome
Sex-linked inheritance: ,N = allele for normal color visionn = allele for color blindness normal male x normal vision female
(carries allele) XN y
XN
Xn
XN XN XN y
XN Xn Xn y
Normalfemale
Normal female (carries c.b. allele)
Normal male
Affected male
Pedigrees Pedigrees show how a trait is inherited through generations.
used to determine phenotypes and genotypes.
Parts of a Pedigree
Male with trait Unaffected female Marriage line
Unaffected Female carries allele
Male doesn’t show trait
First generation
Second generation
male orfemale?
Normal Vision = N Color blindness = n
is color blind?
what genotype?
what phenotype?
what genotype?
what phenotype?what genotype?
Male
Nope
N
Normal vision
n
color blindnessNn
Color BlindnessCause: sex-linked
recessive1/100 males
have, 1/1000 females
Can’t see red-green, or blue due to a missing protein.
Hemophilia Sex-linked recessive approx. 1/10,000 boys Protein needed for blood
clotting is missing.Affected person can bleed to death from cuts and bruises.Treated with transfusions
of missing protein
X-linked Inheritance pedigree chart
Duchenne Muscular Dystrophy Sex-linked disorder
causes loss of muscles & death (before age 20)
Protein needed for muscle development missing.
Affects 1 in 3000 males.
A very disabling condition in men
Found on the Y-Chromosome
The very tragic disease…hairy ears
symptoms…hairy ears
Only 1 cure known….
Summary Questions
On what chromosome are the genes found that causes color blindness, hemophilia, and Duchenne muscular dystrophy?
a - Y-chromosome c – 1st chromosome
b - X-chromosome d – 23rd chromosomes
Summary Questions
On what chromosome are the genes found that causes color blindness, hemophilia, and Duchenne muscular dystrophy?
a - Y-chromosome c – 1st chromosome
b - X-chromosome d – 23rd chromosomes
Compared to females, males have
a- two X chromosomes
b- less chance of having hemophilia
c- greater chance of being color blind
d- 22 pairs of chromosomes
Compared to females, males have
a- two X chromosomes
b- less chance of having hemophilia
c- greater chance of being color blind
d- 22 pairs of chromosomes
Males tend to show sex-linked traits because
a- sex-linked traits are codominant
b- males have only one X chromosome
c- females have incomplete dominance
d- males have two X chromosomes
Males tend to show sex-linked traits because
a- sex-linked traits are codominant
b- males have only one X chromosome
c- females have incomplete dominance
d- males have two X chromosomes
A sex-linked condition causing muscle loss and early death
a- hemophilia
b- multiple sclerosis
c- muscular dystrophy
d- playing video games
A sex-linked condition causing muscle loss and early death
a- hemophilia
b- multiple sclerosis
c- muscular dystrophy
d- playing video games
From whom do men inherit sex-linked traits such as hemophilia and Duchenne muscular dystrophy from?
a- from both mom and dad
b- from dad only
c- from mom only
d- from grand parents
From whom do men inherit sex-linked traits such as hemophilia and Duchenne muscular dystrophy from?
a- from both mom and dad
b- from dad only
c- from mom only
d- from grand parents