BIO140: Gametogenesis

Gametogenesis

______: Production of mature gametes (sperm and ovum)

Spermatogenesis

______: Production of sperm (testes in humans)

Primary Spematocyte

______: Produced by mitosis, at some point signaled to divide by meiosis

Secondary Spermatocyte

______: Haploid (n) cell produced after meiosis I of the primary spermatocyte, it enters meiosis II

Spermatids

______: Haploid cell (n) produced after meiosis I of the secondary spermatocyte, they are immature and must undergo changes to become sperm.

Maturing process of spermatid into sperm

• Tail/flagellum is built

• Motor is built

  • Uses energy from mitochondria to power rotating motor to rotate the tail

• Cell changes shape to be oval (better movement)

• Removes cell organelles

• Streamlined (only what is needed)—Swim upstream, vaginal fluids, increased chance of reproductive success

Sperm

______: The mature gamete produced during spermatogenesis used for sexual reproduction

Sperm functions

• To trigger completion of Meiosis II in the secondary oocyte

• To deliver its chromosomes to the ovum, which fuses with the ovum chromosomes to create the diploid zygote

Oogenesis

______: Produces the oocyte or ovum, occurs in two distinct steps

Oogenesis — Meiosis I

Occurs before birth in the fetal ovaries. Cells in the fetal ovaries divide by mitosis to create primary oocytes, which then go through _________ to produce secondary oocytes

Oogenesis — Meiosis II

Occurs after contact with a sperm in the ovarian/uterine tube

Pause in Oogenesis

• Saves energy and resources by not finishing oogenesis if reproduction is not going to occur (no sperm present)

• Ensures the person is physiologically mature enough to develop the fetus

Puberty

______: In the context of oogenesis, triggers hormonal/chemical signals to start the processes of ovulation and menstruation

Polar Body

Oogenesis

______: Formed by unequal division of cytoplasm to put most of the cell components (necessary resources) into the large daughter cell (ovum). The ovum needs everything the zygote requires to survive and begin dividing by mitosis, as sperm only brings chromosomes. Contains chromosomes

Ovulation

______: The release of a secondary oocyte from the ovaries to the ovarian tube

Menstruation

______: Release of decidualized uterine tissue through the cervix and vagina

Decidualized Uterine Lining

• Tissue changes and gets thicker and then builds blood vessels

• Tissue becomes the maternal side of the placenta if there is an embryo

• Thick because the embryo implants deeply into the tissue (increased chance of embryo survival)

Deciduous

______: One way development, tissue must be released if there is no embryo

Origins of chromosomes in the zygote

Its the first cell of the next generation, created when a sperm physically fuses with an ovum. It is diploid (2n) because it receives half of its chromosomes from the sperm and half from the ovum, restoring the paired set of chromosomes