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12.1 Chromosomal Inheritance
  • The sex chromosomes determine the sex of the individual; the other chromosomes are called autosomes.
  • Certain traits, unrelated to sex, are controlled by genes located on the sex chromosomes.
  • The discovery of X-linked genes supported the chromosome theory of inheritance.
  • Alleles on the X chromosome have a pattern of inheritance that differs from alleles on the autosomal chromosomes.
  1. What are X-linked genes?
  2. Are recessive phenotypes resulting from X-linked genes more likely to be seen in male or female humans and why?
  3. A couple in which the woman is red-green colorblind and the man has normal color vision have two sons and a daughter. What are the phenotypes and genotypes of the children in regard to color vision and how do you know?
Essential Study Partner Summaries of major points:
  1. Chromosomal theory of inheritance
  2. Sex chromosomes
  3. X-linked alleles
Art Review Art Quizzes
12.2 Gene Linkage
  • All alleles on the same chromosome are said to form a linkage group. Linked genes do not segregate and assort independently.
  • Despite linkage, crossing-over can bring about recombinant gametes and recombinant phenotypes do occur.
  • The percentage of recombinant phenotypes when alleles are linked can be used to map that chromosome
  1. Alleles which tend to be inherited together are called _______________ and are found on the _________________ (same or different) chromosome(s).
  2. Suppose you cross two individuals. You know that the genes you are interested in are on the same chromosome but the offspring show phenotypic ratios more consistent with independent segregation. What might have caused this result?
  3. Linked genes that are more frequently separated during crossing over are _______________ (closer together or farther apart) on the chromosome.
Summaries of major points:
  1. Linkage groups
  2. Chromosome mapping
Art Review
12.3 Changes in Chromosome Number
  • Chromosomal mutations include changes in chromosome number and changes in chromosome structure.
  • Several significant syndromes in humans are due to changes in chromosome number.
  1. A polyploid organism has greater than _______ chromosomes.
  2. Is polyploidy more often found in plants or animals?
  3. What is nondisjunction, how does it happen, and what are the results?
  4. What chromosomal mistake causes Down syndrome?
  5. What is a karyotype?
Essential Study Partner Summaries of major points:
  1. Mutations
  2. Changes in chromosome number
Art Review Art Quizzes Explorations
12.4 Changes in Chromosome Structure
  • Changes in chromosome structure include deletions, translocations, duplications, and inversions.
  • Chromosome rearrangements cause a variety of syndromes in humans.
  1. When the end of a chromosome or some internal portion of the chromosome is lost, it is called _________________.
  2. What is a chromosomal translocation?
  3. The occurrence of a segment more than once on the same chromosome is a ________________.
Essential Study Partner Summaries of major points:
  1. Changes in chromosomal structure
Art Review

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