Biology 1115 Chapter 13

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  1. How are living organisms distinguished?
    by their ability to reproduce their own kind
  2. What is genetics?
    the scientific study of heredity and variation
  3. What is heredity?
    the transmission of traits from one generation to the next
  4. How is variation demonstrated?
    by the differences in appearance that offspring show from parents and siblings
  5. What is asexual reproduction?
    one parent produces genetically identical offspring by mitosis
  6. What is a clone?
    a group of genetically identical individuals from the same organism
  7. what is sexual reproduction?
    two parents give rise to offspring that have unique combinations of genes inherited from two parents
  8. define gene.
    are the units of heredity, and are made up of segments of DNA.
  9. How are genes passed to the next generation?
    through reproductive cells called gametes (sperm and eggs)
  10. one set of ___________ is inherited from each parent.
  11. What is karyotype?
    ordered display of the pairs of chromosomes from a cell
  12. The two chromosomes in each pair are called ______________________.
    homologous chromosomes
  13. What makes the two chromosomes in each pair homologous? (3)
    • same length
    • carry gene controlling the same inherited characters
    • same banding pattern
  14. What are the sex chromosomes called, who do they represent?
    • x: females (XX)
    • y: males (XY)
  15. The 22 pairs of chromosomes that do not determine sex is called?
  16. Each pair of homologous chromosomes includes ____________________.
    one chromosome from each parent
  17. What is a diploid cell (2n)?
    • has two sets of chromosomes
    • for humans, diploid number is 46
  18. What is a haploid cell(n)?
    • a single set of chromosomes
    • in humans, diploid number is 23
  19. A gamete, sperm or egg, is haploid or diploid?
    haploid, single set of chromosomes
  20. What is fertilization?
    is when the gametes come together (the sperm and egg)
  21. What is the fertilized egg called and what does it contain?
    • its called a zygote (diploid)
    • contains one set of chromosomes from each parent
  22. The zygote produces somatic cells by ___________ and develops into an adult. (human life cycle)
  23. At sexual maturity, the ovaries and testes produce what kind of gametes?
    haploid gametes
  24. Gametes are the only type of human cells produced by ____________.
  25. _________ and _________ alternate in sexual life cycles to maintain chromosome number.
    Fertilization and meiosis
  26. In a cell where DNA synthesis has occurred, each chromosome is ___________.
  27. What does each duplicated chromosome consist of?
    It consists of two identical sister chromatids.
  28. What is the first step of meiosis?
    replication of chromosomes
  29. What does the two meiosis stages result in?
    four non-identical daughter cells
  30. How many chromosomes does the daughter cell in meiosis have?
    half as many chromosomes
  31. In general, what happens in the first cell division (meiosis 1)?
    homologous chromosomes separate
  32. What does meiosis 1 result in? what is this division called?
    • results in two haploid daughter cells with duplicated chromosomes
    • called the reductional division
  33. what happens in the second cell division (meiosis 2)?
    sister chromatids separate
  34. What are the results in meiosis 2? What is the division called?
    • results in four haploid daughter cells with unduplicated chromosomes
    • it's called the equational division
  35. Meiosis 1 is preceded by interphase, what happens in this stage?
    chromosomes are replicated to form sister chromatids
  36. What are centrosomes?
    • microtubules organizing centers
    • help organize chromosomes
  37. What are two main things about sister chromatids?
    they are genetically identical and joined at the centromere
  38. What is the main difference between mitosis and meiosis?
    • Mitosis: conserves the number of chromosomes sets, producing cells that are genetically identical to the parent cell
    • Meiosis: reduces the number of chromosome sets from diploid to haploid, producing cells that differ genetically from parent cells
  39. What are the three events that are unique to meiosis, and all three occur in meiosis 1?
    • 1. synapsis and crossing over in prophase 1
    • 2. at metaphase plate there are paired homologous chromosomes, instead of individual replicated chromosomes
    • 3. At anaphase 1, its homologous chromosomes that are separated instead of sister chromatids
  40. ____________ produces in sexual life cycles contributes to evolution
    Genetic variation
  41. What are mutations?
    permanent changes in an organisms DNA
  42. Mutations create different versions of genes called?
  43. ________________ during sexual reproduction produces genetic variation?
    Reshuffling of alleles
  44. What are the three mechanisms that contribute to genetic variation?
    • independent assortment of chromosomes
    • crossing over
    • random fertilization
  45. How do homologous pairs orient at metaphase 1 of meiosis?
  46. What happens in independent assortment?
    the maternal and paternal homologues are separated into different daughter cells independently
  47. What are the number of combinations possible when chromosomes assort independently into gametes?
    2^n where n is the haploid number
  48. What does crossing over produce?
    recombinant chromosomes
  49. What is a recombinant chromosome?
    combine genes inherited from each parent
  50. Where does crossing over occur?
    begins very early in prophase 1
  51. What happens in crossing over?
    homologous portions of two nonsister chromatids trade places
  52. How does crossing over contribute to genetic variation?
    by combining DNA from two parents into a single chromosome
  53. How does random fertilization add to genetic variation?
    because any sperm can fuse with any ovum
  54. How many possible chromosome combinations can the fusion of two gametes without crossing over produce?
    8.4 million
  55. What does natural selection results in?
    results in the accumulation of genetic variations favoured by the environment
  56. Sexual reproduction contributes to the genetic variation in a population, which originates from _____________.
  57. What is a life cycle?
    is the generation-to-generation sequence of stages in the reproductive history of an organism
  58. What is common to all organisms that reproduce sexually?
    the alteration of meiosis and fertilization
  59. In the animal life cycle, which are the only haploid cells?
  60. The gametes fuse to form a?
    diploid zygote
  61. The diploid zygote divides by __________ to develop a multicellular organism.
  62. Which organisms exhibit an alteration in generation?
    plants and some algae
  63. What are the 2 stages the life cycle of plants and some algae include?
    diploid and haploid multicellular stage
  64. What is the diploid organism in a plant life cycle called? This organism undergoes __________to produce haploid spores.
    • sporophyte
    • meiosis
  65. Each spore in a plant life cycle  grows by mitosis to produce a haploid organism called?
  66. A gametophyte makes haploid gametes by?
  67. ___________ of gametes results in a diploid sporophyte.
  68. In most fungi and some protists, the only diploid stage is the ?
    single-celled zygote
  69. What stage does the fungi life cycle NOT include?
    multicellular diploid stage
  70. In the fungi life cycle, the zygote produce haploid cells by?
  71. In the fungi life cycle, each haploid cell grows by mitosis, into a ?
    haploid multicellular organism
  72. In the fungi life cycle, the haploid adult produces gametes by?
  73. Only_________ can undergo mitosis.
    diploid cells
  74. Which life cycle stage is found in plants but not animals?
    Multicellular haploid
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Biology 1115 Chapter 13
2013-11-28 18:48:42
Meiosis sexual life cycles

Meiosis and sexual life cycles
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