Transcript see sex

Warm ups:
1. How many chromosomes do humans have?
2. How many X chromosomes do males have?
3. How many X chromosomes do females have?
Sex linked traits in Genetics
Genetics gets more complex!
There are certain genes that are only on the
sex chromosomes…
X and Y
X chromosome has about 1,100 genes
Y chromosome has about 200 genes
Remember:
- if you are a female, you have two X
chromosomes (XX)
- if you are a male, you have one X and
one Y chromosomes (XY)
Sex Linked Disorders
1. Some conditions are closely linked to the X
and Y chromosomes (although most sex
linked disorders are on the X chromosome)
2. An allele inherited on a sex chromosome is a
sex-linked gene
3. Color Blindness and hemophilia – on x
chromosome
4. If a man inherits an X with the gene on it, he
will have the disease
5. A female has to have two X with the gene
(recessive)
Hemophilia – a sex-linked disorder that
affects the ability to clot your blood.
That means if you get a little cut or a
scratch, you would bleed to death
Color blindness– a sex-linked inability or
decreased ability to see color, or perceive
color differences, under lighting conditions
when color vision is not normally impaired.
- on the “X” chromosome
COLOR BLINDNESS TESTs
9
17
50
18
58
18
• The color blindness test consists of a
set of five charts. Each chart shows
a number in one color on a different
backgound color. People with normal
34 color vision will have no problem
seeing the numbers on the charts,
but people with color blindness will
see only random colored dots.
Seventy-five percent of color blind
people have poor green perception.
Of the remaining, 24% have poor red
perception, and one percent are
affected by a rare tritan type.
25
3
Color blindness test
• The test to the left is
simpler.
The individual with
normal color vision will
see a 5 revealed in the
dot pattern.
An individual with
Red/Green (the most
common) color
blindness will see a 2
revealed in the dots.
1. A mother carries the gene for hemophilia on one of
her X chromosomes. She marries a man with no gene
for this disease. Complete a punnett square to see how
this will affect their offspring. (X = normal , x’ =
hemophilia)
X’
XY
Father = _____
X’X
Mother = ____
25
____ % carrier
25
____ % have hemophilia
75
____ % no gene for
disease
X
X
X X’ X X
Y
X’ Y X Y
2. A mother carries the gene for color blindness and her
husband is color blind. Complete a punnett square to
see how this will affect their offspring. (X = normal , xc =
color blind gene)
X
XcY
Father = _____
c
XX
Mother = ____
25
____ % carrier
50
____ % have color blindness
50
____ % no gene for disease
Xc
Xc
c
XX
c
c
XX
Y
X Y XcY
QUESTIONS!
1. A man has one “X” chromosome with the gene
for hemophilia on it. Does he have the disease?
_________
2. A woman has one “X” chromosome with the
gene for baldness. Does she have the disease?
____________. She is called a ____________
because even though she does not have the
disease, she carries it and can pass it on to her
offspring.
3. A woman has to have ______ “X” genes with
the disease gene in order for her to have the
disease.