Transcript Sex-Linked Pedigrees October 340, 2009

Sex-Linked Pedigrees
October 340, 2009

Objective:
 SWBAT
analyze pedigrees to identify sex-linked
disorders

Catalyst:
Does the pedigree to the right
show dominant or recessive
inheritance?
 Label all the people in this pedigree
as DD, Dd, dd, or D_

Agenda




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
Catalyst
Review EQ from yesterday
Homework Review
Sex-Linked Disorders
Worksheet!
Exit Question
Exit Question From Yesterday

Is this dominant or recessive?

How do you know?
EASY AS PIE

Do you see two parents that are affected make a
kid that is not affected?
 THEN

IT IS DOMINANT!!!
Do you see two parents that are unaffected make a
kid that is affected?
 THEN
IT IS RECESSIVE!!!
Homework Review

Let’s go over number 3 and 4!
First things first?

Why are there just about the same
number of boys and girls in the world?
XY = MALE XX = FEMALE

PUNNETT SQUARE!!!!!!!
Human Karyotype
The sexlinked
traits. You
can find
them here!
Sex Linked

What was an autosome?
 Chromosomes
1-22
 Yesterday,
we did disorders that involved something messed
up on the autosomes.

Today… we are going to do disorders on the sexchromosomes, called sex-linked disorders.
Sex-linked Disorders

Key Point #1:
 Sex-linked
disorders are disorders carried on
the sex chromsomes.
 Luckily,
almost all sex-linked disorders are
carried on the X-chromosome?
SEX-LINKED=X-LINKED!!!!
 Sucks
for girls right? Go males right?
Females are luckier
WRONG!!!
Males=XY
Females=XX

If males get an X with the disorder, they
will have the disorder.
 If females get an X with the disorder,
they have another one that could
dominate the other one out.

Don’t believe me?

How many of you guys know
someone who is colorblind?
How
many are male, how many
are female?
How is allele labeled if diseased???
X = normal
*
X = affected allele
Y = normal
Let’s do a punnett!
Punnett Square of
X
X*
X
X* X
XX
*
XX
Y
X*Y
XY
and XY cross
•50% chance
of the
FEMALES
being
carriers
•50% chance
of the
MALES
being
affected
Real Life Examples of Sex-Linked Traits
Red-green color blindness and
hemophilia are classic examples of
sex-linked traits.
 Most people who have these traits
are men, however, there are some
women who may express them as
they must have received two
recessive alleles for the condition.

Let’s practice the pedigree
Pedigree
Worksheet Time!!

Awesome dude!
Exit Question
Label each person in this sex-linked pedigree