Chapter 12- Meiosis

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Chapter 12- Meiosis
2010-04-17 22:20:16

Exam 3
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  1. What is fertilization?
    when a sperm and egg unite
  2. What is a karyotype?
    the number of types of chromosomes present.
  3. what is a homologous chromosome?
    Chromosomes of the same type
  4. What is a gene?
    a section of DNA that influences hereditary traits
  5. What does it mean to be haploid?
    one of each type of chromosome
  6. What does it mean to be diploid?
    two of each type of chromosome
  7. What does it me to be polyploid?
    3 or more versions of a chromosome
  8. What happens before meiosis occurs (Interphase)?
    each chromosome is diploid parent cell is replicated forming sister chromatids
  9. In animals, daughter cells become what?
  10. 2 haploid gametes fuse during fertilization to become what?
  11. 5 phases of meiosis 1
    early prophase

    late prophase



  12. What happens in early prophase 1?
    chromosomes condense

    nuclear envelope breaks up

    spindle forms

    homologous pairs synapse forming a tetrad
  13. What happens in late prophase 1:
    -non sister chromatids begin to seperate

    -exchange or crossing over occurs when chiasmata are formed during this stage
  14. What happens during metaphase 1:
    pairs of homologs line up at metaphase plate
  15. What happens in Anaphase 1?
    paired homologs seperate and begin to migrate to opposite ends
  16. What happens in Telophase 1/Cytokinesis?
    homologs finish migrating to opposite poles then cytokinesis occurs
  17. end result of meiosis 1?
    one chromosome of each homologous pair is distributed to a different cell
  18. What happens during prophase 2?
    Spindle apparatus forms and attaches to chromosomes?
  19. What happens during metaphase 2?
    replicated chromosomes consisting of 2 sister chromatids line up at metaphase plate
  20. What happens during Anaphase 2?
    sister chromatids seperate and begin moving to different poles
  21. What happens during telophase 2/Cytokinesis?
    Chromosomes finish moving to opposite poles and then the cell divides
  22. End result of meiosis 2?
    4 haploid cells form from one dipolid cell
  23. what is the key difference between mitosis and meiosis?
    homologs pair in meiosis, not in mitosis
  24. What happens during the synape of prophase 1?
    2 pairs of sister chromatids are held together by a network of proteins called synaptonemal complex
  25. What does crossing swap?
    Swaps segment of paternal and maternal chromosomes
  26. What is a gene?
    provides instructions for specifying what particular trait might be in an indivdual
  27. how many genes are there on each chromosome?
    hundreds or thousands
  28. How many different combinations of chromosomes can humans produce?
    8.4 million
  29. crossing over is a form of what?
    genetic recombination?
  30. crossing over produces what?
    new combinations of alleles on the same chromosome
  31. What is outcrossing?
    gametes from different individuals combine to form offspring
  32. how does outcrossing increase genetic diversity?
    because chromosomes of 2 different parents are combined
  33. What is self-fertilization?
    when gametes from the same individual combine
  34. What does John Maynord Smith's mathematical model predict?
    asexually reproducing organisms should reproduce faster and outcompete similar organisms in sexual reproduction
  35. What is the purifying selection hypothesis?
    Natural selection occurs against damaged alleles
  36. What does the Changing Environment Hypothesis state?
    Offspring that are different from their parent are more likely to survive through environmental changes
  37. What is nondisjunction?
    failure of homologous chromosomes to seperate
  38. what is a trisomy?
    2 gametes having an extra copy of a chromosome
  39. what is monosomy?
    2 gametes lacking a chromosome
  40. what are aneuploid zygotes?
    those with too few or too many chromosomes
  41. Where are the most cases of aneuploidy chromosomes found?
    sex chromosomes and chromosome 21