Bell Work

1. Bell Work • Get out homework (phases of meiosis worksheet) • Fill in Meiosis Mitosis Venn Diagram • Please try to think of at least four differences for each and two things they have in common

2. Spermatogenesis VSOogenesis How meiosis is different in males and females.

3. Spermatogenesis • Meiosis in males, process used to create sperm • Males create four sperm cells for each single spermatogonium • Remember the original spermatogonium is diploid, while the resulting four sperm are haploid (have half the DNA) • This process occurs in the seminiferous tubules which make up the testes

4. Spermatogenesis • Seminiferous tubules are the little tubes that curl around to create the testes • If stretched out these could reach 300 to 350 meters • Men can produce an infinite number of sperm in their life time. • They begin producing sperm at puberty because that is when the tubes become hollow

5. Spermatogenesis • The spermatogonium starts on the outside of the tube • As it moves its way to the inner portion of the tube it undergoes meiosis • The four sperm are then released into the inside of the seminiferous tubule.

6. Oogensis • Oogenesis is meiosis in females and produces one egg cell. • Each round of meiosis creates one mature egg cell that can be fertilized and three polar bodies, which cannot be fertilized. • This process occurs in the follicles of the ocary

7. oogenesis • Each female has about 400,000 primary follicles in her ovary at birth. • A female starts producing egg cells at puberty and cannot possibly produce more egg cells than she has follicles • Most female produce about 400 mature eggs in her lifetime • During ovulation the egg is released from the ovary so it can be fertilized

9. Main Differences • Creates four mature sperm • Occurs continuously • Occurs throughout entire life after puberty • Occurs in males • Sperm are smaller and motile • Creates one mature egg and three polar bodies • Occurs once a month • Stops occurring once menopause is reached • Occurs in females • Egg is much larger and not motile Spermatogenesis Oogenesis

10. Similarities • Both are forms of meiosis • Both create sex cells used in sexual reproduction • Both occur in the gonads • Both start with a diploid cell and end up with haploid cells. • Both occur in plants (pollen or spores and egg instead of sperm and egg) and animals

11. Problems during Meiosis • Most issues during gamete formation occur during meiosis I • As a woman gets older there become more and more genetic abnormalities in her eggs, which is why the chances of bearing a child with birth defects increase as a woman gets older. • Sometimes during meiosis the chromosomes do not separate causing the egg or sperm to either have 46 or 0 chromosomes • Sometimes only one pair of chromosomes does not separate causing the egg or sperm to have 47 or 45 chromosomes.

12. Problems during Spermatogenesis • Sometimes sperm do not form properly • When this occurs it can lead to infertility • Even though sperm are being produced, they might be slow or not motile. • This causes them to die before they could possible reach the egg