Transcript Sex Linked Inheritance - Mrs. Edwards' Classes

Sex Linked Inheritance:
(why females are superior to males)
(just kidding)
(no, but seriously)
(ok, I am kidding)
(or am I?)
Warm Up
• What % probability will a child be born a
male? Female?
• How could we set up a punnett square to
show this?
Cornell Notes
• Read pages 170-171
• In the margin of your
paper, define the bold
terms.
• In the large portion of
your paper, discuss 3
main points.
• On the bottom,
summarize in 3 sentences
what you read.
The difference between males and
females.
• Females have 2 X
chromosomes.
• They always give one X
to their offspring.
• The X chromosome has
more information than
the Y. That’s why
females are superior to
males.
• Males have 1 X
chromosome and 1 Y
chromosome.
• They can give either to
offspring.
Human Genome
Autosomes
(1 – 22)
Sex Chromosomes
(X and Y)
X
Y
Human Y-chromosome
SRy locus
Males have sperm cells which may have an X
chromosome or a Y chromosome. Male gametes
(sperm) determine the gender of the offspring when
the egg is fertilized.
Punnett Square to determine gender.
• A male gamete XY
chromosomes fertilizes the
egg (XX).
• What is the chance that the
offspring will be female?
Punnett Square to determine gender.
X
• A male gamete XY
chromosomes fertilizes the
egg.
X
X
Y
Punnett Square to determine gender.
• A male gamete XY
chromosomes fertilizes the
egg.
X
X
X
Y
XX
XY
XX
XY
X chromosomes have
genes that Y
chromosomes don’t.
Baldness
Color Blindness
Duchenne Muscular Dystrophy
Adrenoleukodystrophy
Fragile X Syndrome
• X Chromosomes can be
carriers of certain recessive
traits. In females, the
other X probably does not
have the trait and can over
rule the recessive diseased
trait.
Punnett Square to determine gender.
XB
• A carrier female for
colorblindness, marries a
normal man.
XB
• Will their children be color
blind?
• B= normal
• b= color blind
• Y’s don’t have the trait.
Xb
Y
Punnett Square to determine gender.
XB
• A carrier female for
colorblindness, marries a
normal man.
XB
• Will their children be color
blind?
• B= normal
• b= color blind
• Y’s don’t have the trait.
Y
XBXB XBY
XBXb XbY
Xb
Punnett Square to determine gender.
XB
• Normal Female
• Normal Male
• Carrier Female (isn’t
colorblind)
• Colorblind Male
XB
XBXB XBY
XBXb
Xb
Y
XbY
Inheritance patterns:
• Sex-linked recessive conditions
The disease is never passed from father to
son.
Males are much more likely to be affected
than females.
•All affected males in a family are related
through their mothers.
Trait or disease is typically passed from an
affected grandfather, through his carrier
daughters, to half of his grandsons.
PRACTICE
On your pink sheet of paper… practice
the following…