3.4.2 + 3.5.1

  1. What happens to the DNA as it continuously keeps getting replicated?
    • it shortens
    • *that is why they have an "age" limit to how many times they can be replicated
  2. (telomere replication) first step
    -when RNA primer is removed from the 5 end of the laggin strand, a strand of aprent DNA remains unreplicated
  3. (telomere replication) 2nd step (2(
    -telomerase binds to the overhanging section of single stranded DNA

    -telomerase adds deoxyribonucloetides to the end of the parent DNA to extend it
  4. (telomere replication) 3rd step
    -telomerase moves down the DNA strand and adds additional repeats
  5. (telomere replication) 4th step
    • primase, DNA polymerase, and ligase then synthesize the laggin strand in the 5 to 3 direction
    • *this restores the original length of the chromosome
  6. Does telomerase enzyme put an RNA primer or does it have one in its structure?
    it has one in it
  7. Stress AND size of telomere
    The more stress a person has the smaller the telomere will be
  8. The shorter the telomeres length is...the
    less likely of a risk to get aging related diseases
  9. Definition of meiosis
    nuclear division that results in cells having half as many chromosomes as the parent cell
  10. In animals when does meiosis occur?
    • prior to the formation of eggs and sperm
    • *when these two combine the chromosome levels are restored
  11. What is leading hypothesis for meiosis?
    genetically variable offspring are more likely to thrive in changing environments
  12. What are homologous chromosomes?
    • chromosomes of the same type
    • *maternal and paternal that code for G in karyotype
  13. What is an allele?
    • different versions of the same gene
    • *the stretch in DNA that codes for same function
    • **they do not necessairly have to code for same thing
    • **one can code for blue eyes and the other brown eyes
  14. What is a karyotype?
    • number and type of chromosomes present
    • *not everyone has 23 type and 46 chromosomes
  15. What are considered haploid cells?
    • sperm and egg
    • *they only have one version of chromosome
  16. WHat is haploid?
    it is number of distinct types of chromosomes
  17. What does a chromosome do berfore undergoing meiosis?
  18. IN meiosis what happens? (2)
    • -parent cells that contains a pair of homologs are seperated into daughter cells.
    • *one homolog goes into one daughter cell

    • -the sister chromatids in daughter cells seperate creating 4 daughter cells
    • *gametes
  19. what does meiosis mean?
    to lessen
  20. During meiosis I, how many different ways can tetrads line up before they separate?
  21. What is gametogenesis?
    the haploid cells that were produced in meiosis go on to produce either sperm or eggs
  22. When does a haploid become a diploid?
    during fertilization
  23. How does a zygote become a diploid adult?
    through mitosis
  24. (steps to meiosis) first step: (3)

    -chromosomes replicate in parent cell

    -they are in a uncondensed state
  25. (steps to meiosis) step 2 (5)
    early prophase I

    -chromosomes condense

    -nuclear envelope breaks up

    -spindle apparatus forms

    -synapsis of homologs
  26. (steps to meiosis) Late prophase I
    -crossing over of non-sister chromatids
  27. Closer look at synapsis. what happens during synapsis?
    • homologs are held together by proteins in the synaptonemal complex
    • *during prophase I
  28. closer look at crossing over. What ahppens during crossing over? (2)
    -complex of proteins forms where crossing over will occur

    -chromosome segments are swapped between non-sister chromatids
  29. When dpes synapsis and crossing over occur?
    prophase I
  30. (steps to meiosis) step 4
    metaphase I

    -tetrads migrate to metaphase plate
  31. (steps to meiosis) step 5
    anaphase I

    -homologs separate and begin moving to the opposite sides of cell
  32. (steps to meiosis) step 6
    telophase I and cytokinesis

    -chromosomes move to the opposite sides of cell then the cell divides
  33. (steps to meiosis) 7th step
    meiosis II, Prophase II

    spindle apparatus forms
  34. (steps to meiosis) 8th step
    meiosis II, Metaphase II

    • -chromosomes line up at middle of cell
    • *metaphase plate
  35. Small summary of Meiosis II
    sister chromatids separate
  36. Small summary of Meiosis I
    Homologous chromosomes separate
  37. Small summary of prior to meiosis
    -chromosomes replicate which forms sister chromatids
  38. What is Aneuploidy?
    condition in which cells have too many or too few chromosomes
  39. (aneuploidy) Turner syndrome (2)
    "XO" sex chromosomes

    - she is a female with many physical and mental complications
  40. (aneuploidy) Kinefeiter syndrome (2)

    -it is a male with female characteristics
  41. What is trisomy?
    • having 3 chromosomes per number
    • *3 13s
  42. (trisomy)Chromosome number 21 (2)
    -has the most cases

    -down syndrome
  43. Down syndrome AND age of mother
    the older the mother is the higher risk the child will have down syndrome
  44. Why is chromosome 21 the most prevalent and not the other chromomes for trisomy?
    the other ones typically are rarely born. they die
Card Set
3.4.2 + 3.5.1
dna synthesis and meiosis