Biology 1115 Chapter 15

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Biology 1115 Chapter 15
2013-11-30 20:18:15
chromosomal basis inheritance
The chromosomal basis of inheritance
Show Answers:

  1. Where are genes located?
    on a chromosome
  2. Explain how the behaviour of chromosomes during meiosis accounts for Mendel's two laws of inheritance.
    • Law of segregation: when homologous chromosomes separate
    • Law of independent assortment: the way homologous chromosomes line up at the metaphase plate independently which gives a variety of gametes
  3. Who was Thomas Hunt Morgan?
    he provided the first solid evidence associating a specific gene with a specific chromosome by experimenting on fruit flies
  4. What are 3 characteristics that make fruit flies a convenient organism for genetic studies?
    • they breed at a high rate
    • a generation can be bred every two weeks
    • they have only 4 pairs of chromosomes
  5. In Morgan's experimental evidence, the normal phenotype's that were common in the fly population was called?
    wild type
  6. In Morgan's experimental evidence, traits that were alternative to the wild type were called?
    mutant phenotype
  7. How did Morgan's findings support the chromosome theory of inheritance?
    Morgan determined that the white-eyes mutant allele must be located on the X chromosome
  8. Where are the sex linked chromosomes located?
    X chromosome
  9. How are the X and Y sex chromosomes homologous?
    only the ends of the Y chromosome have regions that are homologous with the X chromosomes
  10. What is the SRY gene?
    It's a gene on the Y chromosome that codes for the development of testes
  11. A gene located on either sex chromosome is called?
    sex-linked gene
  12. True or false. The sex chromosomes have genes for many chromosomes unrelated to sex.
  13. In humans, sex-linked usually refers to a gene the?
    X chromosome
  14. What are 3 disorders caused my recessive alleles on the X chromosomes in humans? Who are these more common to?
    • colour blindness
    • Duchenne muscular dystrophy
    • hemophilia
    • more common to men
  15. Why are sex-linked recessive disorders much more common in males than in females?
    this is because a female need two copies of the allele and male needs only one copy of the allele, that's why it's more common in males
  16. What is the X inactivation in mammalian females?
    one of the 2 X chromosomes in each cell is randomly inactivated during embryonic development
  17. What happens to the inactive X chromosome?
    it condenses into a Barr body, which is no longer functional
  18. If a female is heterozygous for a particular gene located on the X chromosome, what happens to her character?
    she will be mosaic for that character
  19. What are linked genes?
    genes located on the same chromosome that tend to be inherited together
  20. Morgan noted that the flies body colour and wing size did not assort independently and reasons that?
    they were on the same chromosome
  21. What is genetic recombination?
    the production of offspring with combinations of traits differing from either parent
  22. Define parental types.
    offspring with a phenotype matching one of the parental phenotypes
  23. Define recombinant types or recombinants.
    Offspring with nonparental phenotypes (new combinations of traits)
  24. What does a 50% frequency of recombination mean?
    it's the frequency of recombinants observed for any two genes on different chromosomes
  25. Morgan proposed that some process must sometimes break the physical connection between genes on the same chromosome, what was this mechanism?
    crossing over of homologous chromosomes
  26. In a genetic map, the further apart two genes are? (2)
    the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency
  27. Genes that are far apart on the same chromosome can have a recombination frequency of what?
    near 50%
  28. what happens in nondisjunction?
    pairs of homologous chromosomes do not separate normally during meiosis
  29. What can result from nondisjunction?
    one gamete can receive two of the same type of chromosome and the other gamete receives no copy
  30. Define aneuploidy. What happens to the offspring with this condition?
    • results from the fertilization of gametes in which nondisjunction occurred
    • offspring have an abnormal number of a particular chromosome
  31. what is a monosomic zygote?
    has only one copy of a particular chromosome
  32. what is trisomic zygote?
    has three copies of a particular chromosome
  33. Define polyploidy.
    is a condition in which an organism has more than two complete sets of chromosome
  34. define triploidy and tetraploidy.
    • triploidy: 3 sets of chromosomes
    • tetraploidy: 4 sets of chromosomes
  35. Polyploidy is more common in?
  36. which are more normal in appearance, aneuploidy or polyploidy?
  37. Breakage of chromosomes can lead to 4 types of changes in chromosome structure, what are they?
    • deletion: removes a chromosomal segment
    • duplication: repeats a segment
    • inversion: reverses a segment within a chromosome
    • translocation: moves a segment from one chromosome to another
  38. What is down syndrome?
    an aneuploidy condition that results from three copies of chromosomes 21.
  39. What is the correlation between down syndrome of child and mother's age?
    frequency of down syndrome increases with the age of the mother
  40. what is klinefelter syndrome?
    result of an extra chromosome in a male, producing XXY individuals.
  41. what is
  42. what is monosomy X (turner syndrome)?
    produce X0 females, who are sterile.
  43. would you expect females with trisomy X to exhibit major phenotypic differences from normal females?
    no because one X will become dysfunctional and form a Barr body
  44. What are the 2 normal exceptions to Mendelian genetics?
    • 1. genes located in the nucleus
    • 2. genes located outside the nucleus
  45. what is genomic printing?
    genomic printing involves the silencing of certain genes that are "stamped" with an imprint during gamete formation
  46. it appears that genomic imprinting is the result of?
    the methylation, addition of CH3 of DNA
  47. normal development requires that embryonic cells have ______________ of certain genes.
    exactly one active copy
  48. what are extranuclear or cytoplasmic genes?
    genes found in organelles in cytoplasm
  49. Extranuclear genes are inherited ___________. Why?
    • maternally
    • because zygote's cytoplasm comes from the egg