BIOL 341: UNIT 3

• In what body part do sperm develop?

  Sperm develop within the testes.
• Why is the cooler environment of the scrotum essential for sperm maturation?

  It is essential for the proper maturation of sperm cells.
• Where are sperm cells stored after their initial development?

  Sperm cells are stored in the epididymis.
• In what body part do oocytes develop?

  Oocytes develop in the ovaries.
• How many immature oocytes does a newborn girl have in her ovaries?

  A newborn girl has approximately a million immature oocytes.
• What happens to the mature oocyte after it is released from the ovaries?

  It travels through the uterine tubes for potential fertilization.
• What are the similarities and differences between male and female reproductive systems?

  Similarities:

  • Both have paired gonads (testes in males, ovaries in females).
  • Both feature tubular structures for transporting gametes.
  • Hormones regulate gamete maturation and reproductive functions.

  
  

  Differences:

  • Males produce sperm continuously; females release one oocyte per cycle.
  • Male structures are external; female structures are internal.
  • Distinct processes: ejaculation in males vs. menstruation in females.
• What are homologous pairs in genetics?

  Homologous pairs are chromosome pairs with the same genes in the same order but may carry different alleles.
• What does polyploid mean in genetics?

  Polyploid refers to a cell with more than two sets of chromosomes.
• What is the outcome of fertilization without meiosis?

  The fertilized ovum would have 92 chromosomes.
• What is the overview of meiosis?

  • Meiosis consists of two main divisions: meiosis I and meiosis II.
  • Meiosis I reduces the number of replicated chromosomes from 46 to 23.
  • Meiosis II produces four haploid cells from one diploid cell.
• What are the stages of meiosis I?

  1. Interphase: DNA replication occurs.
  2. Prophase I: Chromosomes condense, homologous chromosomes pair, crossing over occurs.
  3. Metaphase I: Tetrads align along the metaphase plate.
  4. Anaphase I: Homologous chromosomes are pulled apart.
  5. Telophase I: Nuclear envelope may reform, and cytokinesis occurs.
• What are the stages of meiosis II?

  1. Interphase II: No DNA replication occurs.
  2. Prophase II: Chromosomes condense again.
  3. Metaphase II: Replicated chromosomes align at the metaphase plate.
  4. Anaphase II: Sister chromatids are pulled apart.
  5. Telophase II: Nuclear envelope reforms, and cytokinesis occurs.
• What is the end result of meiosis?

  The net result is four genetically distinct haploid cells.
• What is the difference between haploid and diploid cells?

  Haploid cells contain one set of chromosomes (23), while diploid cells contain two sets (46).
• How does meiosis maintain the chromosome number across generations?

  Meiosis reduces the diploid number to haploid, restoring diploid number during fertilization.
• What are the two mechanisms that generate genotypic diversity during meiosis?

  Crossing over and independent assortment generate genotypic diversity.
• What is independent assortment in meiosis?

  Independent assortment is the random distribution of alleles into gametes during meiosis.
• What are the differences between mitosis and meiosis?

  • Mitosis: one division; Meiosis: two divisions.
  • Mitosis: two daughter cells; Meiosis: four daughter cells.
  • Mitosis: daughter cells genetically identical; Meiosis: daughter cells genetically different.
  • Mitosis: chromosome number same as parent (2n); Meiosis: half the number (1n).
  • Mitosis: occurs in somatic cells; Meiosis: occurs in germline cells.
  • Mitosis: occurs throughout life; Meiosis: completes after sexual maturity.
  • Mitosis: used for growth and repair; Meiosis: used for sexual reproduction.
• What are spermatogonia and oogonia?

  Spermatogonia and oogonia are specialized diploid stem cells that produce gametes.
• How do spermatogonia ensure continuous sperm production?

  They undergo mitotic division to produce one daughter cell that develops into sperm and another that remains a stem cell.
• What are the steps of sperm and oocyte formation and specialization?

  Spermatogenesis:

  1. Spermatogonia divide to form primary spermatocytes.
  2. Primary spermatocytes undergo meiosis I to form secondary spermatocytes.
  3. Secondary spermatocytes undergo meiosis II to become spermatids.
  4. Spermatids differentiate into mature spermatozoa.

  
  

  Oogenesis:

  1. Oogonia grow into primary oocytes.
  2. Primary oocytes divide into a polar body and secondary oocyte.
  3. Secondary oocyte continues to meiosis II, resulting in another polar body and the mature ovum.
• How do the timetables of spermatogenesis and oogenesis differ?

  Spermatogenesis begins at puberty and continues throughout life, while oogenesis starts in the female fetus and resumes monthly after puberty.
• How do paternal and maternal age effects differ in terms of genetic conditions?

  Maternal age effects are linked to chromosomal imbalances, while paternal age effects involve mutations in sperm.
• At what point in prenatal development does an embryo become a fetus?

  An embryo becomes a fetus at the end of the eighth week of prenatal development.
• What is the significance of the transition from embryo to fetus in prenatal development?

  • Marks the end of the embryonic period.
  • Indicates the beginning of fetal development.
  • Fetus undergoes further growth and organ development.
• How do paternal and maternal age effect conditions differ?

  Paternal and maternal age effects differ in their mechanisms and outcomes.
• What are maternal age effects associated with?

  Maternal age effects are associated with chromosomal imbalances in oocytes.
• What leads to errors in chromosome segregation during meiosis in older mothers?

  Prolonged arrest at prophase I leads to errors in chromosome segregation.
• What condition can result from maternal age effects?

  Down syndrome (trisomy 21) can result from maternal age effects.
• What do paternal age effects involve?

  Paternal age effects involve the accumulation of mutations in sperm.
• Why are older fathers more likely to pass on dominant mutations?

  Older fathers are more likely to pass on dominant mutations due to frequent cell divisions of spermatogonia.
• At what point does an embryo become a fetus?

  An embryo becomes a fetus at the end of the eighth week of prenatal development.
• What are the key events of fertilization?

  • Millions of sperm are deposited in the vagina.
  • Capacitation activates the sperm.
  • Sperm penetrates the corona radiata.
  • Enzymes from the acrosome break through the zona pellucida.
  • Sperm membrane fuses with the oocyte membrane.
  • A wave of electrical activity prevents other sperm from entering.
  • Nuclei disassemble and chromosomes merge to form a zygote.
• What is a zygote?

  A zygote is the single-cell entity formed when a sperm fertilizes an oocyte.
• What is a morula?

  A morula is a solid ball of cells resembling a mulberry formed from a zygote.
• What is a blastocyst?

  A blastocyst is characterized by a fluid-filled center and an inner cell mass that will form the embryo.
• What is the significance of the inner cell mass in a blastocyst?

  The inner cell mass distinguishes cells within the blastocyst and marks the beginning of embryonic development.
• How are some genes silenced during development?

  Some genes are silenced through methylation, which inhibits their expression.
• What are the primary germ layers?

  The primary germ layers are ectoderm, endoderm, and mesoderm.