Sections 9.21-9.23
Sections 9.21-9.23
Sections 9.21-9.23
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<strong>9.21</strong>-<strong>9.23</strong> Warm-Up<br />
How is sex determined in humans? Chickens?<br />
Explain monoecious and hermaphroditic.<br />
What is a sex-linked gene? Give an example.<br />
Name 3 sex-linked human disorders discussed in the<br />
book.<br />
1. humans - xy, chickens - zw
Chromosomes determine sex in<br />
many species<br />
Section <strong>9.21</strong>
sex determination in humans is XY<br />
X Y<br />
Male<br />
Boy or Girl?<br />
(male)<br />
Sperm<br />
Parents’<br />
diploid<br />
cells<br />
Offspring<br />
(diploid)<br />
(female)<br />
Egg
Some Plants use the XY System<br />
Spinach<br />
Marijuana<br />
Date Palm
The X-O system<br />
The Z-W system<br />
Chromosome number<br />
Other systems of sex determination exist in other animals and plants<br />
XO - grasshoppers, crickets, and roaches (sex determined by sperm)<br />
ZW - wild strawberry, fish, butterflies, and birds (sex determined by egg)<br />
chromosome # - ants and bees (males are haploid - come from unfertilized egg)
If You Produce Both<br />
Sperm and Eggs...<br />
monoecious - term for plants that produce both<br />
gametes (corn)<br />
hermaphroditic - animals that produce both<br />
gametes (earthworms and snails)
Sex-linked genes exhibit a<br />
unique pattern of inheritance<br />
Section 9.22
Sex-Linked Gene<br />
any gene located on a sex chromosome<br />
those genes unrelated to sex determination<br />
are often on the X chromosome
Fruit Fly Eye Color is Sex-Linked
Female Male Female Male Female Male<br />
X R X R<br />
X R<br />
X R X r<br />
X r<br />
X r Y<br />
X R Y<br />
Y<br />
R = red-eye allele<br />
r = white-eye allele<br />
X R X r<br />
notice the symbols used for sex-linked alleles<br />
Fruit Fly Eye Color<br />
X r<br />
X R<br />
X R X R<br />
X R<br />
X R Y<br />
X r X R X R Y<br />
X r Y<br />
Y<br />
X R X r<br />
X r<br />
X R<br />
X R X r<br />
X r<br />
X r X r X R Y<br />
X r Y<br />
X r Y<br />
Y
Connection: Sex-linked<br />
disorders affect mostly males<br />
Section <strong>9.23</strong>
Advantage...Female<br />
males are more likely to show a recessive sex-<br />
linked trait<br />
they only get 1 allele because they only have<br />
one X chromosome (the Y chromosome does<br />
not have an allele)
Sex-Linked Recessive<br />
Human Disorders<br />
Red-Green Colorblindness<br />
Hemophilia<br />
Duchenne Muscular Dystrophy<br />
colorblind - malfunction of light sensitive cells in the eyes (several X genes involved)<br />
hemophilia - have an abnormal allele for a factor involved in blood clotting<br />
muscular dystrophy - progressive weakening and loss of muscle tissue (wheelchair by 12, death by 20<br />
due to difficulty breathing)
What do you see?<br />
If you are red-green color blind you will not see the 7
A high incidence of hemophilia has plagued the royal families.<br />
Queen<br />
Victoria<br />
Albert<br />
Alice Louis<br />
Alexandra Czar<br />
Nicholas II<br />
of Russia<br />
Alexis
Homework:<br />
Finish Packet Exercises and Multiple Choice<br />
Questions<br />
Study for Exam
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