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Meiosis and the Creation of Sex
Cells in Sexually Reproducing
Organisms
Sex Chromosomes
Sex-Linked Disorders
Pedigrees - Genetic Counseling
Selective Breeding
Ch 5 Sec. 3 pages126 - 132
Human Body Cells have 23
Pairs of Chromosomes one of
Each Pair Contributed By Each
Parent Sex Cell
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Human Sex Cells Include
Sperm and Egg
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SPERM
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EGG
Animal Sexual Reproduction
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Plant Sexual Reproduction
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Meiosis I
The creation of a sex cell requires that a normal diploid body
cell undergo Meiosis I forming two haploid daughter cells. No
replication of DNA takes place before the cell undergoes the
second step Meiosis II. In humans this process takes place in
the testes of males and in the ovaries of females.
Meiosis II
During the second step Meiosis II the Two Daughter Cells divide
again into 4 haploid daughter cells. This process makes sperm
and eggs
Fertilization in Humans
23 + 23 = 46 chromosomes
23 Chromosomes Haploid Sperm Cell
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23 Chromosomes Haploid Egg Cell
Fertilization in Plants
Haploid Pollen Grain
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Haploid Ovum
Anotomys leander
92 Chromosomes (Diploid)
_______ Haploid Sex Cell
African Wild Dog
78 Chromosomes (Diploid)
_______ Haploid Sex Cell
Bean
22 Chromosomes (Diploid)
_______ Haploid Sex Cell
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Cabbage
_____ Chromosomes (Diploid)
9
Haploid Sex Cells
Fruit Fly
_____ Chromosomes (Diploid)
4
Haploid Sex Cells
Cotton
52
Chromosomes (Diploid)
Kangaroo
12
Chromosomes (Diploid)
______ Haploid Sex Cells
______ Haploid Sex Cells
Human Sex Chromosomes
Female XX Male XY
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Pedigree
A diagram that shows the occurrence of a genetic trait
in several generations of a family
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Pedigree Chart
Pedigree Chart
Symbols
Sex Linked Disorders
Sex-linked disorders are related to the sex chromosomes. These
disorders, (also called X-linked), are recessive, involve the X
chromosome, and affect males almost exclusively. Females are
virtually never affected by these disorders because they possess
two X chromosomes, both of which would have to carry the
defective gene in order for it to be manifested. Since these
females' fathers would be affected by the disorder, which is
usually debilitating or fatal, this is a highly unlikely situation.
EXAMPLES
1. Duchene muscular dystrophy, a progressive degeneration of muscle
tissue
2. fragile-X syndrome, a common form of mental retardation in boys
3. hemophilia, a disease in which a deficiency in one of several bloodclotting factors causes uncontrollable bleeding
4. Colorblindness - people have trouble distinguishing between shades of
red and green
5. Male patterned baldness -
Queen Victoria and Prince Albert’s
Family
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Queen Victoria and Prince Albert’s
Family Pedigree Hemophilia
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Selective Breeding
Humans organizes the mating of
organisms with desirable traits.
Animals
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Plants