Chapter 6 Biology

  1. Telomeres
    • a protective cap at the end of the DNA
    • every time a cell divides the telomere gets a bit shorter
    • when the telomere becomes too short, the cell dies
  2. Cancer
    • cells that rebuild the telomere with each division can become cancerious
    • cells that have forgotten how to die
    • unrestrained cell growth and division
    • can lead to tumors
    • second leading cause of death in US
  3. Prokaryotic Chromosomes
    • genetic info is carried in a single circular chromosome
    • this strand of DNA is attached at one site to the cell membrane
  4. Eukaryotic Chromosomes
    • genetic info is organized into linear chromosomes
    • eukaryotic chromosomes float freely in the nucleus
  5. Binary Fission
    • prokaryotes divide by binary fission
    • bacteria divide by binary fission
    • circular chromosome duplicates itself and the cell splits into two indentical new cells
    • asexual reproduction (daughter cells inherit their DNA from single parental cell)
  6. Cell Division
    • occurs in the mitotic phase
    • the rest of the cycle is called interphase (two gap phases for growth, synthesis phase for replication of DNA)
  7. Eukaryotic Cell Cycle
    • Gap 1: cell's primary growth phase. Normal cellular functions (making proteins, getting rid of waste, etc) take place
    • DNA Synthesis: cell begins preparations for division. Every chromosome creates an exact duplicate of itself in a process called replication
    • Gap 2: Second period of growth and preparation for cell division.
    • Mitosis: cell's nucleus duplicates, then divides
    • Cytokinesis: cell then duplicates, forming two separate cells
  8. Replication
    • the process of DNA duplication
    • cell division is preceded by replication
    • unwinding then rebuilding (enzyme connects appropriate complementray base to the exposed base)
  9. Complementarity
    characteristic that in the double-stranded DNA molecule the base on one strand always has the same pairing-partner (called complementary base) on the other strand
  10. Pairs
    • Adenine to Thymine
    • Guanine to Cytosine
  11. Mutation
    • errors in replication can lead to changes in the DNA sequence called mutations
    • several DNA repair processes occur after replication
    • if error remains, the sequences in a replicated DNA molecule can be different from those in the parent molecule
  12. Mitosis
    • most cells are not immortal: mitosis generates replacements
    • two reasons for mitosis: growth and replacement
  13. Apoptosis
    A form of cell death in which a programmed sequence of events leads to the elimination of cells without releasing harmful substances into the surrounding area. Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells, unnecessary cells, and unhealthy cells. PROGRAMMED DEATH
  14. Mitosis
    • cells duplicate themselves, occurs in four steps then followed by the replication of chromosomes
    • 1. chromosomes condense
    • 2. all of the duplicated and condensed pairs of chromosomes move to the center of the cell
    • 3. each chromosome is pulled apart from its duplicate
    • 4. new cell membranes form around each complete set of chromosomes and the cytoplasm duplicates as well
    • one parent cell becomes two daughter cells
  15. Interphase
    • first step in mitosis (preparation)
    • chromosomes replicate in preparation for mitosis
    • long, linear chromosomes that have replicated condense
  16. Centromere
    joint between two sister chromatids
  17. Prophase
    • nuclear membrane breaks down
    • sister chromatids (replicated chromosomes) condense
    • spindle forms
  18. Metaphase
    • sister chromatids line up at the center of the cell
  19. Anaphase
    • sister chromatid pairs are pulled apart by the spindle fibers
    • One full set of chromosomes goes to one side of the cell and another identical set goes to the other
  20. Telophase
    • chromosomes begin to uncoil as the nuclear membrane is reassembled around them
  21. Cytokinesis
    • cytoplasm and organelles duplicate and are divided into approximately equal parts
    • cell splits into two
  22. Metastasis
    cancer cells can separate from a tumor and spread throughout the body via the circulatory system
  23. Sexual Reproduction
    • requires special cells made by meiosis (generates sperms and eggs)
    • diploid cells: two copies of each chromosome
    • haploid cells: one copy of each chromosome
  24. Meiosis
    • starts with a diploid cell (from gonads)
    • gametes: special reproductive cells (gametes are produced through meiosis)/ have only half as many chromosomes as the rest of the cells in the body
    • you have two copies of every gene
    • reduces amount of genetic material in gametes (gametes have half as much genetic material as the parent cell)
    • produces gametes that all differ from each other with respect to the combinations of alleles they carry (gametes carry different combinations of alleles)
  25. Homologues and Sister Chromatids
    • Homologues are the maternal and paternal copies of a chromosome
    • A sister chromatid is a chromosome and its identical duplicated version held together at a centromere
  26. Meiosis (2)
    • cells undergoing meiosis divide twice (4 total)
    • interphase: each chromosome in a homologous pair replicates to form a sister chromatid
    • meiosis I: homologous pairs seperate
    • meiosis II: sister chromatids seperate. results in four haploid cells, two contain a single copy on one of the original chromosomes and the other two contain a single copy of the other chromosome
  27. Prophase I
    • most complex of all phases of meiosis
    • replicated chromosomes condense
    • spindle is formed
    • nuclear membrane disintegrates
  28. Metaphase I
    each pair of homologous chromosomes moves to the equator of the cell
  29. Anaphase I
    • beginning of the first cell division that occurs during meiosis
    • homologues are pulled apart toward opposite sides of the cell
    • maternal and paternal sister chromatids are pulled to the ends of the cell in a random fashion
  30. Telophase I
    • marked by the chromosomes arriving at the two poles of the cell
    • the cytoplasm divides and the cell membrane pinches the cell into two daughter cells
  31. Meiosis Division
    separating the sister chromatids
  32. Prophase II
    • genetic material once again coils tightly making the chromatids visible under the microscope
    • in the brief interphase prior to prophase II there is no replication of any of the chromosomes
  33. Metaphase II
    sister chromatids (each appearing as an X) move to the center of the cell
  34. Anaphase II
    the fibers attached to the centromere begin pulling each chromatid in the sister chromatid pair toward opposite ends of each daughter cell
  35. Telophase II
    the cytoplasm then divides, the cell membrane pinches the cell into two new daughter cells, and the process ends
  36. Crossing over
    crossing over during meiosis produces a mixture of maternal and paternal genetic material on each chromatid
  37. Reassortment of Homologues
    the homologues and sister chromatids distributed to each daughter cell during meiosis are a random mix of maternal and paternal genetic material
  38. Alleles come from two parents
    each parent donates his or her own set of genetic material
  39. Sexual reproduction (offspring genetically different )
    • crossing over in the production of gametes
    • shuffling and reassortment of homologues during meiosis
    • combining alleles from two parents at fertilization
  40. Sex of Offspring
    • in humans, male if the Y chromosome is present
    • in birds, female if W chromosome is present
    • presence or absence of sex chromosomes
    • number of chromosome sets
    • environmental factors
  41. Karyotype
    • a display of an individuals complete set of chromosomes
    • can be used to identify abnormalities in a fetus's chromosomes early in development
    • Down Syndrome: Trisomy 21 (caused by having an extra copy of chromosome 21)
  42. Amniocentesis, CVS
    • amniotic fluid: contains many cells from the fets (four months into pregnancy)
    • tissue is removed from the placenta
    • because the fetus and placenta both develop from the same fertilized egg, their cells contain the same genetic composition
    • can be done several weeks earlier in the pregnancy, usually between 10 and 12
  43. Nondisjunction
    • unequal distribution of chromosomes during meiosis
    • error of cell division that creates a gamete with zero or two copies of a chromosome rather than a single copy
  44. Too Many of Too Few Sex Chromosomes
    • Turner Syndrome: X_, short height, web of skin between neck and shoulders, underdeveloped ovaries (sterile), learning difficulties
    • Klinefelter Syndrome: XXY, underdeveloped, testes, lower testosterone, some female features, long limbs, slightly taller
    • XYY Males: taller than average, acne, lower intelligence
    • XXX Females: may be sterile, no obvious physical or mental problems
Card Set
Chapter 6 Biology
Chapter 6 Biology