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