Pedigrees and Sex Linked Traits

OutcomeI will explore how traits are inherited through generations by solving autosomal and sex-linked pedigrees.

Sex Chromosomes

X and Y are sex chromosomes The other 22 pairs are

autosomal(body) chromosomes Males = XY Females = XX Not true homologous pairs

– X has more genes

X and Y

Males – Get Y from dad– Get X from mom

Females– Get one X from dad– Get one X from mom

Sex-linked traits

X-linked– The inheritance

pattern of genes located on the X chromosome

Hemophilia Video

https://www.phd.msu.edu/divisions/pediatric-adolescent-hematology-oncology/educational-videos-about-hemophilia.html

XH Xh

Xh XH Xh Xh Xh

Y XH Y Xh Y

X-Linked Punnett Square

• What is the chance that their son will have hemophilia?

• What is the chance that their daughter will have hemophilia?

50%

50%

Sex linkedH=normal & h=hemophilia

Cross: XHXh x XhY

Sex-linked worksheet

Working with your table, complete the sex linked worksheet in your notes.

You will have 6 minutes!

Pedigrees

a chart that shows how a trait (phenotype) is inherited through a family

Pedigrees

circles: females squares: males shaded: individual

with trait/disease Half-shaded: carriers

for a trait but does not express the trait.

Generation / Individual Practice

Generations are the rows in a pedigree

Individuals are labeled across a pedigree

Lines down represent offspring

I

II

III

1 2

1 2 3

1 2 3 4

Quick Quiz

Individual A is

a. A male who expresses the trait

b. A female who does not express the trait

c. A male who does not express the trait

d. A female who does express the trait

What do we call this individual? Carrier

Quick Quiz

Individual D is

a. A male who expresses the trait

b. A female who does not express the trait

c. A male who does not express the trait

d. A female who does express the trait

Quick Quiz

Individual H is

a. A male who expresses the trait

b. A female who does not express the trait

c. A male who does not express the trait

d. A female who does express the trait

Outcome

I will explore how traits are inherited through generations by solving autosomal and sex-linked pedigrees.

Fugates of Kentucky: Skin Bluer than Lake Louise

http://www.youtube.com/watch?v=4iJVWMR4Uq0

Fugates of Kentucky: Skin Bluer than Lake Louise

Methemoglobinemia blood disorder with an abnormal amount of

methemoglobin - a form of hemoglobin reduced ability to release oxygen to tissues - gives

blood a bluish color

Autosomal Recessive

Trait appears only when two parents by chance carry the hidden allele

Affected individual inherits both recessive alleles

Example: sickle cell disease Who could be a carrier?

Autosomal Dominant

Trait appears in every generation, in about half of descendants (assuming a heterozygous carrier)

Affected individual has at least one dominant allele

Example: Huntington’s disease

X-linked Recessive

Mother passes on to half of sons;half of daughters carry it.  Father never passes on trait.

Examples: Hemophilia, color blindness Why do more men have it? Who could be a carrier? Can men be carrier?

X-linked Dominant

Father passes trait to all daughters; no sons.  Mother passes on to half of children.

Example: Rett syndrome

Outcome

I will explore how traits are inherited through generations by solving autosomal and sex-linked pedigrees.