Podcast
Questions and Answers
What phase of the cell cycle is characterized by the synthesis of DNA?
What phase of the cell cycle is characterized by the synthesis of DNA?
Which checkpoint is responsible for assessing DNA quality before synthesis?
Which checkpoint is responsible for assessing DNA quality before synthesis?
During which phase do cells check for sufficient organelles and cytoplasm before division?
During which phase do cells check for sufficient organelles and cytoplasm before division?
How many chromosomes do human germ cells contain?
How many chromosomes do human germ cells contain?
Signup and view all the answers
What is the role of cyclins in the cell cycle?
What is the role of cyclins in the cell cycle?
Signup and view all the answers
What is the main protein involved in the quality control of the G1/S checkpoint?
What is the main protein involved in the quality control of the G1/S checkpoint?
Signup and view all the answers
At the end of the S phase, how many chromatids does a human cell have?
At the end of the S phase, how many chromatids does a human cell have?
Signup and view all the answers
Which phase of the cell cycle is NOT part of interphase?
Which phase of the cell cycle is NOT part of interphase?
Signup and view all the answers
What does Mendel’s Second Law of Independent Assortment state?
What does Mendel’s Second Law of Independent Assortment state?
Signup and view all the answers
During which phase of meiosis do homologous pairs align at the metaphase plate?
During which phase of meiosis do homologous pairs align at the metaphase plate?
Signup and view all the answers
What occurs during Anaphase I of meiosis?
What occurs during Anaphase I of meiosis?
Signup and view all the answers
What is the significance of disjunction during meiosis?
What is the significance of disjunction during meiosis?
Signup and view all the answers
What phase follows Telophase I in meiosis?
What phase follows Telophase I in meiosis?
Signup and view all the answers
How many daughter cells are produced at the end of Meiosis II from a single gametocyte?
How many daughter cells are produced at the end of Meiosis II from a single gametocyte?
Signup and view all the answers
What term describes males having only one copy of a gene on their X chromosome?
What term describes males having only one copy of a gene on their X chromosome?
Signup and view all the answers
What genetic makeup defines females in terms of their sex chromosomes?
What genetic makeup defines females in terms of their sex chromosomes?
Signup and view all the answers
What is the primary role of Sertoli cells in the testes?
What is the primary role of Sertoli cells in the testes?
Signup and view all the answers
What type of cells secrete testosterone in the male reproductive system?
What type of cells secrete testosterone in the male reproductive system?
Signup and view all the answers
What is the final product of spermatogenesis?
What is the final product of spermatogenesis?
Signup and view all the answers
Which structure contributes fructose to nourish sperm?
Which structure contributes fructose to nourish sperm?
Signup and view all the answers
Which part of the sperm is responsible for motility?
Which part of the sperm is responsible for motility?
Signup and view all the answers
What is the function of the bulbourethral gland?
What is the function of the bulbourethral gland?
Signup and view all the answers
In females, ovaries are primarily responsible for producing which hormones?
In females, ovaries are primarily responsible for producing which hormones?
Signup and view all the answers
During ejaculation, sperm pass through which of the following ducts before reaching the urethra?
During ejaculation, sperm pass through which of the following ducts before reaching the urethra?
Signup and view all the answers
What is the primary function of the follicles in the ovaries?
What is the primary function of the follicles in the ovaries?
Signup and view all the answers
What triggers the completion of meiosis II in the secondary oocyte?
What triggers the completion of meiosis II in the secondary oocyte?
Signup and view all the answers
Which statement accurately describes primary oocytes?
Which statement accurately describes primary oocytes?
Signup and view all the answers
What structural feature allows for the transport of the ovum in the oviduct?
What structural feature allows for the transport of the ovum in the oviduct?
Signup and view all the answers
How is the polar body formed during oogenesis?
How is the polar body formed during oogenesis?
Signup and view all the answers
What is the role of the zona pellucida in relation to the secondary oocyte?
What is the role of the zona pellucida in relation to the secondary oocyte?
Signup and view all the answers
Which hormone is primarily responsible for initiating the menstrual cycle at puberty?
Which hormone is primarily responsible for initiating the menstrual cycle at puberty?
Signup and view all the answers
What is the final outcome of oogenesis if fertilization does not occur?
What is the final outcome of oogenesis if fertilization does not occur?
Signup and view all the answers
What triggers the production of testosterone in males during puberty?
What triggers the production of testosterone in males during puberty?
Signup and view all the answers
Which hormone is primarily responsible for preparing the uterine lining each month in females?
Which hormone is primarily responsible for preparing the uterine lining each month in females?
Signup and view all the answers
What causes the surge of luteinizing hormone (LH) that induces ovulation?
What causes the surge of luteinizing hormone (LH) that induces ovulation?
Signup and view all the answers
What happens to progesterone levels if implantation of the ovum does not occur?
What happens to progesterone levels if implantation of the ovum does not occur?
Signup and view all the answers
What triggers the follicles to produce estrogen during the follicular phase?
What triggers the follicles to produce estrogen during the follicular phase?
Signup and view all the answers
Which hormone is secreted in response to follicle-stimulating hormone (FSH) that maintains the female reproductive system?
Which hormone is secreted in response to follicle-stimulating hormone (FSH) that maintains the female reproductive system?
Signup and view all the answers
During which phase do the levels of FSH and LH rise significantly in response to the decrease in estrogen and progesterone?
During which phase do the levels of FSH and LH rise significantly in response to the decrease in estrogen and progesterone?
Signup and view all the answers
What role does the corpus luteum play after ovulation?
What role does the corpus luteum play after ovulation?
Signup and view all the answers
Study Notes
Cell Cycle & Mitosis
- Diploid (2n) cells, like autosomal cells, contain two sets of chromosomes, while haploid (n) cells, like germ cells, contain one set.
- In humans, diploid cells have 46 chromosomes, and haploid cells have 23 chromosomes.
- The cell cycle is the series of events that take place in a cell leading to its division and duplication of its DNA (DNA replication) to produce two daughter cells.
- The four stages of the cell cycle are: G1, S, G2, and M.
- The first three stages (G1, S, and G2) are collectively known as interphase, the longest part of the cell cycle.
- Cells not preparing for division are in the G0 stage, a state that cells can enter from the G1 phase.
- Chromosomes are not visible during interphase because they are in a less condensed form called chromatin.
- During the G1 stage (Presynthetic Growth), the cell focuses on:
- Increasing in size
- Producing organelles like mitochondria, ribosomes, and endoplasmic reticulum
- Preparing for DNA replication
- If the cell has enough resources and DNA quality is satisfactory, it will move into the S phase.
- During the S stage (Synthesis of DNA), the cell replicates its genetic material:
- Each chromosome duplicates, creating two identical sister chromatids attached at the centromere.
- The ploidy (number of chromosome sets) remains the same, but the number of chromatids doubles. (46 chromosomes but 92 chromatids in human cells)
- During the G2 stage (Postsynthetic Growth), the cell:
- Double checks for any errors in DNA replication.
- Ensures it has enough organelles and cytoplasm to divide.
- After passing the checkpoint, the cell enters the M phase.
- The M stage (Mitosis) consists of two main processes:
- Mitosis: the division of the nucleus and its chromosomes into two daughter nuclei.
- Cytokinesis: the division of the cell's cytoplasm and organelles.
- Mitosis is divided into four phases:
- Prophase: chromosomes condense, the nuclear envelope breaks down, and the spindle begins to form.
- Metaphase: chromosomes align at the metaphase plate (center of the cell), and each sister chromatid is connected to a spindle fiber from opposite poles.
- Anaphase: sister chromatids separate at their centromeres and are pulled to opposite poles by the spindle fibers.
- Telophase: chromosomes reach the poles, decondense, the nuclear envelope reforms, and the spindle disappears. Cytokinesis typically overlaps with telophase.
Control of the Cell Cycle
- Checkpoints exist between the G1/S phase and the G2/M phase to ensure proper cell cycle progression.
- The G1/S checkpoint (restriction point) determines if the DNA is suitable for replication:
- The p53 protein plays a crucial role in this checkpoint.
- If DNA damage is detected, the cell cycle pauses until the damage is repaired.
- The G2/M checkpoint ensures the cell has enough organelles and sufficient size to divide.
- The cell cycle is controlled by cyclins and cyclin-dependent kinases (CDKs):
- CDKs are enzymes that require the presence of specific cyclins to be activated.
- The concentration of cyclins fluctuates throughout the cell cycle, regulating CDK activity.
Meiosis
- Meiosis is a specialized cell division that produces gametes (sperm and egg cells).
- Meiosis consists of two rounds of division: Meiosis I and Meiosis II.
-
Meiosis I is the reductional division, where the number of chromosomes is halved.
- Prophase I: Homologous chromosomes pair up and exchange genetic material through crossing over.
- Metaphase I: Homologous pairs align at the metaphase plate, attached to spindle fibers from opposite poles.
- Anaphase I: Homologous pairs separate, and each chromosome is pulled towards opposite poles. This process is known as disjunction and accounts for Mendel's First Law of Segregation.
- Telophase I: Nuclear envelopes reform, cytokinesis occurs, and two haploid daughter cells are formed.
-
Meiosis II is the equational division, similar to mitosis, where sister chromatids separate.
- Prophase II: Nuclear envelopes break down, and spindle fibers form.
- Metaphase II: Sister chromatids line up at the metaphase plate, attached to spindle fibers from opposite poles.
- Anaphase II: Sister chromatids separate at their centromeres and are pulled to opposite poles.
- Telophase II: Nuclear envelopes reform, cytokinesis occurs, and four haploid daughter cells are formed.
Linkage
- Linkage refers to the tendency of genes located close together on the same chromosome to be inherited together.
- The closer the genes are, the less likely they are to be separated by crossing over during meiosis.
- The further apart the genes are, the more likely they are to be separated.
The Reproductive System
- Biological sex is determined by the 23rd pair of chromosomes.
- XY: Male
- XX: Female
- Females have two X chromosomes, while males have one X and one Y chromosome.
- The X chromosome carries a significant amount of genetic information, and mutations in X-linked genes can lead to sex-linked disorders.
- Males are hemizygous for X-linked genes, meaning they only have one copy, making them more susceptible to recessive disorders.
- Females can be heterozygous or homozygous for X-linked genes, making them less prone to expressing recessive disorders since they have two copies.
Male Reproductive Anatomy
- The testes are the male gonads responsible for producing sperm and testosterone.
- Testes consist of:
- Seminiferous tubules: where sperm is produced, nourished by Sertoli cells.
- Interstitial cells (cells of Leydig): secrete testosterone and other androgens.
- Testes are located in the scrotum, an external pouch that keeps a slightly lower temperature than the body, which is optimal for sperm development.
- Sperm travels through the following structures after production:
- Epididymis: where sperm mature and gain motility.
- Vas deferens: transports sperm from the epididymis to the ejaculatory duct.
- Ejaculatory duct: merges with the urethra.
- Seminal fluid is produced by the following accessory glands:
- Seminal vesicles: contribute fructose for sperm nourishment.
- Prostate gland: provides an alkaline environment for sperm survival.
- Bulbourethral glands (Cowper's glands): secrete a clear fluid to neutralize urine and lubricate the urethra.
Spermatogenesis
- Spermatogenesis is the process of sperm production, occurring in the seminiferous tubules.
- Diploid spermatogonia undergo mitosis to produce more spermatogonia.
- Spermatogonia differentiate into diploid primary spermatocytes.
- Primary spermatocytes undergo meiosis I to produce haploid secondary spermatocytes.
- Secondary spermatocytes undergo meiosis II to produce haploid spermatids.
- Spermatids mature into functional spermatozoa.
- Each spermatogonium gives rise to four functional sperm cells.
- Sperm consists of three parts:
- Head: contains genetic material, covered by an acrosome cap for penetrating the egg.
- Midpiece: filled with mitochondria to provide energy for movement.
- Flagellum: tail for movement.
Female Reproductive System
- The female reproductive system consists of internal organs.
- The ovaries are the female gonads, producing eggs (ova) and hormones like estrogen and progesterone.
- Ovaries are located in the pelvic cavity and contain numerous follicles.
- Follicles are multilayered sacs that nourish and protect immature ova.
- One egg is ovulated per month into the peritoneal sac.
- The fallopian tubes (oviducts) transport the egg towards the uterus.
- Cilia lining the fallopian tubes propel the egg forward.
- The uterus is the site of fetal development. The lower end of the uterus is the cervix, which connects to the vaginal canal.
- The vulva is the external female anatomy.
Oogenesis
- Oogenesis is the production of female gametes (eggs).
- A woman has a finite number of egg cells (oogonia) formed during fetal development.
- By birth, all oogonia have undergone DNA replication and are considered primary oocytes.
- Primary oocytes are diploid (2n) and arrested in prophase I of meiosis.
- Once a woman enters puberty, one primary oocyte completes meiosis I each month, producing a secondary oocyte and a polar body.
- Secondary oocyte receives most of the cytoplasm, while the polar body is small and usually does not divide further.
- The secondary oocyte is arrested in metaphase II.
- The secondary oocyte is surrounded by the:
- Zona pellucida: an acellular layer of glycoproteins that protects the oocyte and contains sperm binding sites.
- Corona radiata: an outer layer of cells surrounding the zona pellucida.
- Meiosis II is triggered when a sperm cell penetrates the two layers. The secondary oocyte completes meiosis II, producing a mature ovum and another polar body.
- The mature ovum is large because it contains all the necessary organelles, cytoplasm, half the DNA, RNA, and physical space for the zygote.
- Upon fertilization, the haploid sperm nucleus and the haploid ovum nucleus fuse, forming a diploid zygote.
Sexual Development
- The hypothalamus restricts gonadotropin-releasing hormone (GnRH) production before puberty.
- The release of GnRH triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
Male Sexual Development
- The presence of the Y chromosome leads to androgen production during the 9th week of fetal development.
- Androgen production remains low during infancy and childhood.
- Testosterone production increases dramatically during puberty.
- FSH stimulates Sertoli cells, promoting sperm maturation.
- LH stimulates interstitial cells to produce testosterone.
- Testosterone develops and maintains the male reproductive system and secondary sexual characteristics.
Female Sexual Development
- Estrogen is secreted in response to FSH and promotes:
- Development and maintenance of the female reproductive system.
- Development of female secondary sexual characteristics.
- Progesterone is secreted by the corpus luteum (the remnant follicle after ovulation).
- Controlled by LH.
- Responsible for development and maintenance of the endometrium (uterine lining) after its initial growth by estrogen.
- After the first trimester, the placenta takes over progesterone production.
The Menstrual Cycle
-
The menstrual cycle is a monthly recurring process characterized by the shedding of the uterine lining (menstruation).
-
The menstrual cycle consists of three phases:
-
Follicular Phase:
- GnRH secretion from the hypothalamus increases in response to low estrogen and progesterone levels towards the end of the previous cycle.
- FSH and LH increase, stimulating the development of several ovarian follicles.
- Estrogen levels rise as follicles mature, causing negative feedback on GnRH, LH, and FSH.
- Estrogen stimulates the growth of the uterine lining (endometrium) by promoting blood vessel formation and glandularization of the decidua.
-
Ovulation:
- The follicles secrete high estrogen levels, eventually reaching a threshold and triggering a surge in GnRH, LH, and FSH.
- The LH surge directly stimulates ovulation, the release of the mature egg (secondary oocyte) from the dominant follicle into the peritoneal cavity.
-
Luteal Phase:
- The ruptured follicle transforms into the corpus luteum under LH stimulation.
- The corpus luteum produces progesterone, and progesterone levels rise while estrogen levels remain high.
- Progesterone, along with estrogen, suppress LH and FSH, preventing ovulation of more eggs.
-
-
Menstruation:
- If fertilization does not occur, corpus luteum degrades, and progesterone levels decline.
- The uterine lining, deprived of progesterone support, sheds off, resulting in menstruation.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the key concepts of the cell cycle and mitosis, including the differences between diploid and haploid cells, stages of the cell cycle, and the significance of interphase. Test your knowledge on how cells prepare for division and the roles of different phases in cellular processes.
