Questions and Answers
What is the outcome of meiosis?
Crossing over occurs in anaphase I of meiosis.
False
What is the role of Sertoli cells in the male reproductive system?
To nourish developing sperm.
The main hormone responsible for the maintenance and development of male secondary sex characteristics is __________.
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What triggers ovulation in the menstrual cycle?
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Match the hormone with its function:
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During which stage of meiosis are homologous chromosomes separated?
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The corpus luteum produces estrogen and progesterone mainly during the follicular phase.
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In oogenesis, the oocyte undergoes cytokinesis evenly.
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What hormone does the blastula produce to maintain the corpus luteum after fertilization?
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What triggers the release of testosterone in males?
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During menopause, the ovaries stop producing __________ and __________.
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The __________ is the site where sperm are deposited during intercourse.
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Match the following phases of the menstrual cycle with their key characteristics:
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Which hormone is primarily responsible for maintaining the uterine lining during the luteal phase?
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What type of cells are produced during spermatogenesis?
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High levels of estrogen and progesterone have a negative feedback effect on GnRH, LH, and FSH.
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What are common physical changes accompanying menopause?
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The decidua undergoes __________ and __________ during the follicular phase due to estrogen stimulation.
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At what age range does menopause typically occur?
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What is the main difference between diploid and haploid cells?
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The G1 stage of the cell cycle is where DNA replication occurs.
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What does p53 do in the cell cycle?
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During the S stage, the strands of DNA are held together at the __________.
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Match the following cell cycle stages with their functions:
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What phase follows metaphase in mitosis?
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Cancer occurs when cell cycle control is functioning properly.
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What is produced at the end of mitosis?
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Cells in the G0 stage perform their functions without preparing for __________.
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What role do cyclins play in the cell cycle?
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Study Notes
Cell Types and Cycle
- Diploid (2n) cells contain two copies of each chromosome; haploid (n) cells have one copy.
- The cell cycle comprises five stages: G1, S, G2, M, and G0.
- G1 stage involves cell growth and organelle production, preparing for DNA synthesis.
- S stage is where DNA replication occurs, forming sister chromatids held at the centromere.
- G2 stage includes further cell growth and organelle replication, with quality control before mitosis.
- M stage encompasses mitosis and cytokinesis, resulting in two identical diploid daughter cells.
- G0 stage is a non-dividing phase where cells perform regular functions.
- p53 plays a critical role in cell cycle checkpoints, particularly G1 to S and G2 to M.
- Cyclins and cyclin-dependent kinases (CDKs) regulate progression through the cell cycle.
Mitosis
- Mitosis consists of four phases: prophase, metaphase, anaphase, and telophase.
- In prophase, chromosomes condense, the nuclear membrane dissolves, and centriole migration occurs.
- Metaphase features chromosomes aligning along the metaphase plate.
- Anaphase involves separation of sister chromatids to opposite poles.
- Telophase sees the reformation of the nuclear membrane and division of cytosol and organelles during cytokinesis.
Meiosis
- Meiosis occurs in gametocytes and results in four haploid gametes.
- It involves one round of replication followed by two divisions: meiosis I and II.
- Prophase I features synapsis, where homologues intertwine, forming tetrads.
- Crossing over during prophase I provides genetic diversity, following Mendel’s second law.
- In metaphase I, homologous chromosomes align on the metaphase plate; in anaphase I, they are pulled apart.
- Meiosis II resembles mitosis, separating sister chromatids.
Reproductive System
- Human biological sex is determined by the 23rd chromosome pair: XX for females, XY for males.
- X-linked mutations can lead to sex-linked disorders, more commonly affecting males due to hemizygosity.
- The Y chromosome contains the SRY gene, which differentiates gonads into testes.
- Sperm develop in the seminiferous tubules of the testes, nourished by Sertoli cells.
- Leydig cells produce testosterone, essential for male secondary sex characteristics.
- Sperm mature in the epididymis and are transported through the reproductive tract during ejaculation.
- Seminal vesicles and the prostate gland contribute fluids that nourish and alkalinize semen during ejaculation.
Spermatogenesis
- In spermatogenesis, a spermatogonium yields four haploid sperm.
- Germ cells transition from primary spermatocytes to secondary spermatocytes after meiosis I, and to spermatids after meiosis II.
- After maturation, spermatozoa have a head (containing genetic material and acrosome), midpiece (ATP generation), and flagellum (motility).
Oogenesis
- Oogenesis occurs in the ovaries, producing one ovum and polar bodies from an oogonium.
- At birth, primary oocytes are arrested in prophase I and later mature into secondary oocytes, halted at metaphase II until fertilization.
- Zona pellucida and corona radiata protect and support the oocyte during fertilization.
- Hormones regulating the reproductive cycle include GnRH, FSH, and LH, influencing both male and female reproductive functions.
Menstrual Cycle
- The menstrual cycle involves a periodic endometrial lining growth and shedding.
- Follicular phase stimulated by GnRH leads to FSH and LH secretion, promoting follicle development.
- Ovulation occurs due to an LH surge triggered by elevated estrogen levels.
- In the luteal phase, the corpus luteum secretes progesterone, sustaining the uterine lining.
- Menstruation happens if fertilization does not occur, leading to a drop in estrogen and progesterone.
Menopause
- Menopause typically occurs between ages 45 and 55, signifying the end of reproductive capability.
- Ovarian hormone production ceases, leading to an increase in FSH and LH levels.
- Accompanying changes include hot flashes, bloating, headaches, and mood swings.
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Description
Explore the fundamental concepts of the cell cycle, including diploid and haploid cells, interphase stages such as G1, S, and G2, and the crucial processes that take place during each phase. Understand how cells prepare for division and the importance of the restriction point in maintaining DNA integrity.
