1. Asexual v. Sexual:
    number of parents?
  2. Asexual v. Sexual:
    result of what?
    • a: mitosis
    • s: fusion of sex cells from each parent
  3. Asexual v. Sexual:
    • a: identical
    • s: distinct; variation among offspring
  4. Human somatic cells have __ of chromosomes. 
    The two chromosomes in each pair are called __.
    • 23 pairs
    • homologous chromosomes, or homologs
  5. True or False:
    Chromosomes in a homologous pair carry genes controlling different inherited traits.
    • false
    • Chromosomes in a homologous pair carry genes controlling different inherited traits.
    • Chromosomes in a homologous pair carry genes controlling the same inherited traits.
  6. True or False: 
    Homologous pairs of chromosomes carry genes controlling the same inherited characters, but not necessarily the same information for those characters.
  7. In a diploid cell:
    how many pairs
    how many sets
    • 1 pair
    • 2 sets (maternal, paternal)
  8. In a haploid cell:
    how many pairs
    how many sets
    • no pairs 
    • one set
  9. Human somatic cells (2n) have __ chromosomes. 
    Human somatic cells have __ of homologous chromosomes. 
    Human __ number is __.
    • 46
    • 23 pairs (2 sets)
    • 2n 
    • 46
  10. Human gametes (1n) have __ chromosomes. 
    Human gametes have __ of homologous chromosomes.
    Human __ number is __.
    • 23
    • 0 pairs (1 unpaired set)
    • 1n 
    • 23
  11. As in mitosis, what must occur with DNA first?
    DNA replication
  12. Meiosis consists of how many cell divisions?
  13. Meiosis begins with a __ cell (pairs of homologous chromosomes) and produces __ (only one chromosome from each homologous pair).
    • 2n
    • 4 1n
  14. Explain meiosis I.
    • homologous chromosomes separate
    • Meiosis I results in two haploid daughter cells with replicated chromosomes
    • Meiosis I= reduction division
    • The number of chromosoems are reduced from 2n to 1n
  15. At the end of meiosis I, we have?
    • haploid cells with replicated chromosomes
    • (2-chromatid chromosomes)
  16. At the end of meiosis II, we have __.
    haploid cells with unreplicated chromosoems
  17. What occurs in prophase?
    • DNA supercoils and chromosomes are visible
    • Synapsis: homologous chromosoems move beside each other
  18. Each pair of chromosomes forms a __, a group of 4 chromatids (4 DNA molecules)
  19. In prophase:
    __: chromatids cross over each other and exchange DNA segments
    __: X-shaped regions of tetrad where crossing over of DNA occurs.
    • recombination
    • chiasma
  20. Where does crossing over occur?
    at the ends; only the ends
  21. In metaphse I, what occurs.
    tetrads line up at the metaphse plate
  22. In anaphase I, what occurs?
    sister chromatids remain attached, but homologous chromosomes separate
  23. Between Meiosis I and II:
    DNA Replication (does/ does not) occur
    S phase (does/ does not) occur between divisions.
    This is not __. It is called __
    • DNA Replication (does/ does not) occur
    • S phase (does/ does not) occur between divisions.
    • interphase 
    • interkinesis
  24. What is different about metaphase II and metaphase of mitosis?
    because of crossing over in meiosis I, the two sister chromatids of each chromosome are no longer genetically identical
  25. At the end of emiosis, there are what?
    four daughter cells, each with a haploid set of unreplicated chromosomes, each genetically distinct from the others and from the parent cell
  26. Mitosis __ the number of chromosome sets, producing cells that are __ to the parent cell. 
    • conserves
    • genetically identical
  27. Meiosis __ the number of chromosome sets, producing cells that are __ from each other and from the parent cell
    • reduces from two to one
    • genetically different
  28. __ are the original source of genetic diversity. 
    They create different versions of genes called __.
    • mutations 
    • alleles
  29. Reshuffling of __ during sexual reproduction produces __.
    • alleles
    • genetic variation
  30. What are the three mechanisms that contribute to genetic variation?
    • independent assortment of chromosomes
    • crossing over
    • random fertilizatioin
  31. What is independent assortment?
    homologous pairs of chromosomes orient randomly at metaphse I of meiosis
  32. The number of combinations possible when chromosomes assort independently into gametes is __.  For humans, there are more than __ possible combos of maternal and paternal chromosomes.
    • 2n
    • 8 million 
  33. When does crossing over occur?
    What happens?
    • prophase one
    • homologous portions of two nonsister chromatids trade places
  34. After crossing over occurs, how do the chromosomes look?
    one recombinated sister chromatid, one original
  35. Where is the only place DNA is switched at?
  36. What is random fertilization?
    any sperm can fuse with any egg, producing a zygote with any of about 70 trillion combinations
  37. Explain the animal life cycle.
    • 2 1n cells fuse-->
    • 1 2n zygote-->
    • mitosis creates a multicellular diploid organism-->
    • sex cells undergo emiosis to produce gametes
    • only the haploid cells are gametes
  38. will gametes ever reproduce again in the aniimal life cycle?
  39. The life cycle of plants includes both a __ and __.
    diploid (sporophyte stage) and haploid multicellular (gametophyte) stage
  40. True or False:
    Spores are gametes.
    • False:
    • Spores are NOT gametes
  41. Explain the plant life cycle.
    • Zygote reproduces by mitosis-->
    • diploid sporophyte stage--> 
    • meiosis-->
    • haploid spores-->
    • mitosis-->
    • gametophyte stage-->
    • gametes-->
    • mitosis-->
    • fertilization--> 
    • zygote
  42. The diploid organism in plants is the __ and makes __ by __.
    • sporophyte 
    • haploid spores
    • meiosis
  43. Spores grow by __ into a __= __. It makes __ by __.
    • mitosis
    • haploid organism
    • gametophyte
    • haploid gametes
    • mitosis
  44. __ of gametes results in a diploid __.
    • fertilization
    • sporophyte
Card Set