Spermatogenesis and Oogenesis Flashcards

Meiosis Review

• Complete the meiosis Atomy quiz to check your understanding.
• Practice content regularly to prevent it from becoming "rusty", especially after moving on from unit three.
• Reviewing topics covered a while ago can be very effective for exam preparation.

Production of Sperm Cells and Egg Cells

• Spermatogenesis: production of sperm cells
• Oogenesis: production of egg cells
• Differences exist in the production of sperm cells versus egg cells.
• Syllabus point: Compare and contrast spermatogenesis and oogenesis with reference to haploid and diploid cells within the context of meiosis I and II.
• Egg cells need to carry the genetic material, energy stores, and organelles required for the early development of a zygote.
• Sperm cells primarily need to carry genetic material and be able to reach the egg.

Oogenesis

• Oogenesis is female gamete production.
• Meiosis in oogenesis results in one large, viable egg instead of four equal haploid cells.
• The other three haploid cells are called polar bodies, which degenerate and their components are reused.
• Polar bodies carry genetic material but have an uneven distribution of cytoplasm and organelles, making them non-viable.
• This process ensures the best quality and chance of survival for the single egg, which is crucial due to the finite number of eggs a female has.
• Females produce all their eggs before birth or in the early stages, whereas sperm cells are continuously produced from puberty until death.
• Menopause occurs when there are no more eggs to be released.

Oogonium

• Oogonia (pre-egg cells) undergo mitosis before meiosis one.
• Mitosis produces two oocytes.

Process of Oogenesis

• Begins during fetal development, where diploid (2n) oogonia are formed by mitosis.
• From one oogonium, two egg cells are produced, one from each oocyte.
• Cells begin meiosis one but are arrested in prophase one until puberty.
• At puberty, follicles develop each month in response to follicle-stimulating hormone (FSH).
• The follicle completes the first meiotic division into two cells of unequal size.
• A larger cell with more cytoplasm and organelles, and a first polar body, which degenerates.
• The larger cell forms the secondary oocyte.
• The secondary oocyte begins meiosis two but is paused in metaphase two until fertilization.
• The egg is released from the ovary and travels through the fallopian tubes.
• If fertilization occurs, meiosis two continues.
• After every division results in polar bodies.
• There are three polar bodies and one large viable egg cell for every oocyte.

Diagrammatic Representation

• Diagrams may represent polar bodies differently, but remember there are always three polar bodies and one viable egg.
• There are clear pauses/development at certain level and then wait for the next hormone to be released to push development on.

Spermatogenesis

• Spermatogenesis is the production of sperm in the seminiferous tubules of the testes.
• Spermatogenesis begins at puberty.
• Each dividing cell produces four functional sperm cells of approximately the same size.
• Spermatogenesis is continuous, unlike the monthly release of eggs.

Process

• Spermatogenesis begins with the mitotic division of diploid spermatogonium.
• Mitosis at the beginning of meiosis means the first stage spermatocyte produces 2 of them, so from one spermatogonia, eight sperm are produced.
• Meiosis one and meiosis two result in four haploid spermatid cells.
• Spermatids differentiate into sperm by losing most of their cytoplasm and gaining a flagellum.
• Losing cytoplasm reduces water resistance for swimming.
• The sperm structure's only goal is to carry genetic material and swim fast.

Summary

• Comparing spermatogenesis and oogenesis involves understanding haploid and diploid cells.

Comparison

• Sperm is small with no food source.
• Egg is larger with its own energy/food source.
• Sperm is mobile, and the egg is not.
• Sperm is made in the male gonads (testes), and the egg is made in the female gonads (ovaries).
• Sperm production occurs from puberty until death.
• Females are born with a full complement of eggs and do not make new ones.
• Both sperm and ova (eggs) are haploid.
• Haploid means having half the normal genetic material (a single set of chromosomes).
• Four sperm are produced from a meiotic division, while one ovum is produced from a meiotic division.

Action Items

• Submit a Venn diagram comparing mitosis and meiosis to demonstrate understanding.