Unit 3

• DNA


  Double helix structure composed of two long strands twisted around each other, made up of nucleotides consisting of a sugar molecule, a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G)
• DNA


  • Adenine pairs with thymine (A-T), and cytosine pairs with guanine (C-G), forming complementary base pairs
• DNA function

  Stores genetic information that determines an organism's traits and characteristics, serves as the code for building proteins essential for various cellular processes
• DNA replication


  Process by which DNA is copied to produce identical DNA molecules, occurs during all cell division, ensuring each new cell receives a complete set of genetic information
• Fertilization

  Fusion of a sperm cell with an egg cell, resulting in the formation of a zygote

  
• Female reproductive organs

  • Ovaries
  • Fallopian tubes (oviducts)
  • Uterus
  • Cervix
  • Vagina

  
• Ovaries


  Primary female reproductive organs responsible for producing eggs (ova) and hormones such as estrogen and progesterone
• Ovulation


  One egg is released from an ovary each month and travels down the fallopian tube towards the uterus

  
• Fallopian tubes


  Where fertilization typically occurs, as sperm can meet and fertilize the egg while it is in transit

  
• Uterus


  Where a fertilized egg implants and develops into a fetus during pregnancy

  
• Cervix


  Lower part of the uterus that connects to the vagina and acts as a passageway for sperm to enter and menstrual blood to exit
• Vagina


  Muscular canal that extends from the cervix to the outside and serves as the birth canal during childbirth
• Menstruation


  Monthly process where the lining of the uterus is shed if fertilization does not occur, resulting in menstrual bleeding

  
• Hormonal regulation of the menstrual cycle


  Involves interactions between the pituitary gland, ovaries, and uterus

  
• Hormonal balance is essential for the proper functioning of the female reproductive system, influencing menstrual cycles, ovulation, and fertility

  
• Defects or injuries to structures of the female reproductive system, such as blocked fallopian tubes, uterine abnormalities, or hormonal imbalances, can result in fertility problems by stopping ovulation, fertilization, or embryo implantation
• Male reproductive organs


  • Testes
  • Epididymis
  • Vas deferens
  • Seminal vesicles
  • Prostate gland
  • Urethra
  • Penis
• Testes


  Primary male reproductive organs responsible for producing sperm and testosterone
• Spermatogenesis


  Sperm production occurs within the testes
• Urethra


  Serves as a common passage for both urine and semen
• Defects or injury to structures of the male reproductive system, such as blockages in the vas deferens or hormonal imbalances, can result in fertility problems by interfering with sperm production
• Mitosis


  Process of cell division where one diploid parent cell divides into two genetically identical diploid daughter cells

  
• Mitosis


  • Essential for growth, repair, and maintenance of multicellular organisms
• Asexual reproduction


  Involves mitosis and occurs in organisms where offspring are produced from a single parent forming clone offspring

  
• Asexual reproduction


  • Budding in yeast and hydra
  • Binary fission in bacteria

  
• Regeneration


  Process where organisms can regrow lost or damaged body parts through mitotic cell division, as seen in some animals like starfish or lizards
• Meiosis


  Specialized type of cell division that occurs in sexually reproducing organisms, leading to the formation of gametes (sperm and egg cells)

  
• Meiosis


  Involves two cell divisions, resulting in the production of four haploid daughter cells from one diploid parent cell

  
• Meiosis


  • Serves to halve the chromosome number in gametes, ensuring that when fertilization occurs, the resulting zygote has the correct diploid chromosome number
  • Involves homologous chromosomes, which are pairs of chromosomes that carry genes for the same traits, one from each parent
  • Involves a process called crossover or recombination, where homologous chromosomes exchange genetic material, resulting in the mixing of genetic information and increased genetic diversity among offspring

  
• In both mitosis and meiosis, DNA replication occurs prior to cell division, ensuring that each resulting daughter cell inherits a complete and accurate set of genetic information

  
• Menstrual cycle


  Monthly 28-day process regulated by hormones from the pituitary gland, ovaries, and uterus, involving menstruation, the release of an egg (ovulation), and the preparation of the uterus for potential pregnancy

  
• If fertilization does not occur, hormone levels drop, causing the shedding of the uterine lining and initiating a new 28-day cycle

  
• Zygote formation


  During fertilization, gametes unite to form a zygote, containing all genetic information for the offspring. Recombination occurs, mixing genes from both parents, leading to genetic variation crucial for evolutionary change.
• Early development


  Cells formed through mitosis undergo differentiation, becoming specialized for specific functions. Differentiated cells form tissues and organs in multicellular organisms. In embryos, genetic information is initially uniform, but gene activation or deactivation leads to specialization into various cell types.

  
• Environmental influences


  Can affect gene expression, modifying traits in organisms (e.g. fruit flies developing straight wings instead of curly ones in cooler environments, plants producing white instead of green color due to lack of chlorophyll production)
• Placenta


  Vital organ during pregnancy that provides nutrients, oxygen, and hormone production, while acting as a barrier against harmful substances, supporting the development and well-being of the fetus in the uterus

  
• Umbilical cord


  Flexible tube-like structure that connects the developing fetus to the placenta in the uterus during pregnancy, serving as a lifeline for the fetus by providing essential nutrients and oxygen from the mother's bloodstream and transporting waste products and carbon dioxide back to the mother's bloodstream for elimination

  
• Around two months into pregnancy, when major organs have formed, the embryo is referred to as a fetus

  
• Early pregnancy is crucial, as problems with inherited genes or exposure to harmful environmental factors can affect the embryo
• Harmful substances like alcohol, drugs, and tobacco can lead to birth defects and complications, and infections like German measles or AIDS can also harm the embryo or fetus