1. Meiosis 1

2. Meiosis 2

3. Random fertilization
Any 2 parents will produce a zygote with over 70 trillion (223 x 223) diploid combinations

4. Sexual reproduction creates variability
Sexual reproduction allows us to maintain both genetic similarity & differences.
Michael & Kirk Douglas
Baldwin brothers
Martin & Charlie Sheen, Emilio Estevez

5. Mitosis vs. Meiosis

6. Changes in Chromosomes Number
Euploidy = correct # of chromosomes
Aneuploidy = a change in chromosomes number due to non-disjunction during meiosis
Monosomy- only 1 copy of an individual chromosome
Trisomy- 3 copies of an individual chromosome

7. Primary nondisjuction = Meiosis I Secondary nondisjuction = Meiosis II

8. Trisomy 21 : Down Syndrome
Delayed mental and social skills
Decreased muscle tone at birth
Asymmetrical or odd-shaped skull
Small skull
Small mouth with protruding tongue
Broad short hands
Increased risk of developing
Leukemia and Alzheimer’s later in life

9. Trisomy 18 : Edward’s Syndrome
Most children die in the first year of life, some have lived 10 years
Growth deficiency
Feeding difficulties
Breathing difficulties
Developmental delays
Mental Retardation
Overlapped, flexed fingers
Webbing of the second and third toes
Clubfeet
Structural heart defects at birth

10. Trisomy 13 : Patau Syndrome
Mental retardation, severe
Seizures
Small head
Scalp defects
Cleft lip and/or palate
Eyes close set (hypotelorism) –may fuse
Extra digits (polydactyl)
Hernias
Undescended testicle
Children die in the first year of life

11. Procedure: Amniocentesis and Karyotyping

12. Karyotyping

13. https://youtu.be/BD6h-wDj7bw

14. Changes in Sex Chromosome #
SRY gene (located on short arm of Y chromosome)
-hormone= testis-determining factor

15. Turners Syndrome (XO) – missing Barr Body
Kleinfelter’s Syndrome (XXY)
Swyer Syndrome (XY female) Y chromosome is missing the SRY gene - The uterus and fallopian tubes are normally-formed, but the gonads (ovaries or testes) are not functional; affected individuals have undeveloped clumps of tissue called streak gonads. Because of the lack of development of the gonads, Swyer syndrome is also called 46,XY complete gonadal dysgenesis.

16. La Chapelle Syndrome (XX male)
XX male syndrome Caused by unequal crossing over between the X and Y chromosomes during meiosis in the father, which results in the X chromosome containing the SRY gene. When this X combines with a normal X from the mother during fertilization, the result is an XX male.
Poly-X Females (XXX, XXXX)
Triple X syndrome, also called trisomy X or 47,XXX, is characterized by the presence of an additional X chromosome in each of a female's cells. Although females with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most females with triple X syndrome have normal sexual development and are able to conceive children.
Triple X syndrome is associated with an increased risk of learning disabilities and delayed development of speech and language skills. Seizures or kidney abnormalities occur in about 10 percent of affected females.
This condition occurs in about 1 in 1,000 newborn girls. Five to 10 girls with triple X syndrome are born in the United States each day.

17. Jacob’s Syndrome (XYY males)
What is 47,XYY syndrome?
47,XYY syndrome is characterized by an extra copy of the Y chromosome in each of a male's cells. Although males with this condition may be taller than average, this chromosomal change typically causes no unusual physical features. Most males with 47,XYY syndrome have normal sexual development and are able to father children.
47,XYY syndrome is associated with an increased risk of learning disabilities and delayed development of speech and language skills.
A small percentage of males with 47,XYY syndrome are diagnosed with autistic spectrum disorders
This condition occurs in about 1 in 1,000 newborn boys.

18. Chromosomal Mutations

19. Deletion Syndromes
Williams Syndrome (deletion of a piece of chromosome 7)
Cri du chat (cat’s cry) (deletion of a piece of chromosome 5)

20. Spermatogenesis Production of sperm Occurs in the testes
Continuous and prolific
Each ejaculation contains ~ million sperm
Occurs in the testes
Seminiferous tubules

21. Spermatogonia (stem cells that give rise to sperm) are located at the periphery of each seminiferous tubule
Spermatogonia are diploid
Developing sperm move toward the central opening (lumen) of the tubule as they undergo meiosis and differentiation
4 cells result
Develop into mature sperm
Haploid

23. The structure of sperm
Campbell

24. Oogenesis The development of ova
Mature, unfertilized eggs cells
Happens in the ovary
Oogonia (stem cells that give rise to ova)
Multiply and begin meiosis
STOPS at prophase 1
At this phase, the cells are called primary oocytes
Remain in this phase until the onset of puberty, when they are activated by hormones
Activated by LH and FSH

25. Meiosis then STOPS again
Beginning at puberty, FSH periodically stimulates a follicle to grow and induces its primary oocyte to complete meiosis 1 and start meiosis 2
Meiosis then STOPS again
The secondary oocyte, released during ovulation, does not continue meiosis right away
Penetration of the egg cell by sperm triggers the completion of meiosis
Then meiosis is complete
LH stimulates the completion of meiosis

26. Campbell
Growing follicle

28. Major difference #1
1. unevenness in the mitotic division/cytokinesis of oogenesis
Almost all the cytoplasm  1 daughter cell (secondary oocyte)
3 polar bodies which degenerate
Spermatogenesis = four mature sperm

29. Major difference #2
The cells that produce sperm continue to divide by mitosis throughout life (males)
Not the case for women
*born with all the primary oocytes

30. Major difference #3 Oogenesis has long resting periods
Sperm is produced in an uninterrupted sequence