1. 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

2. XN Xn XN y XN Xn XN XN XN y Xn y
Sex-linked inheritance: , N = allele for normal color vision n = allele for color blindness normal male x normal vision female (carries allele)
XN y
Normal
female
Normal male XN Xn
XN XN
XN y
Xn y
XN Xn
Normal female (carries c.b. allele)
Affected male

3. Pedigrees Pedigrees show how a trait is inherited through generations.
used to determine phenotypes and genotypes.

4. Parts of a Pedigree
Male with trait Unaffected female Marriage line Unaffected Female carries allele Male doesn’t show trait
First generation
Second generation

5. n Normal Vision = N Color blindness = n Nope Male Normal vision N
is color blind?
male or
female?
what phenotype?
Male
Normal vision
what genotype?
what genotype? N n
what phenotype?
what genotype?
color blindness Nn

6. Color Blindness Cause: sex-linked recessive
1/100 males have, 1/1000 females
Can’t see red-green, or blue due to a missing protein.
                                          

7. 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

8. X-linked Inheritance pedigree chart

9. 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.

10. A very disabling condition in men
Found on the Y-Chromosome

11. The very tragic disease… hairy ears
symptoms…hairy ears
Only 1 cure known….

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. A sex-linked condition causing muscle loss and early death a- hemophilia b- multiple sclerosis c- muscular dystrophy d- playing video games

20. A sex-linked condition causing muscle loss and early death a- hemophilia b- multiple sclerosis c- muscular dystrophy d- playing video games

21. 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

22. 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