Genetics 8

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Genetics 8
2012-07-15 12:43:03
Dr Troy Bray

Lecture test number two.
Show Answers:

  1. What is a chromosome mutation or chromosomal aberation?
    Large changes in chromosome structure.
  2. What is a genome mutation?
    A change in chromosome number. (change in number of sets or number of individuals in a set)
  3. What are the four chromosomal classifications?
    • Meta
    • Submeta
    • Acro
    • Telocentric 
  4. Describe the chromosomes found in a karyotype.
    • Short p arms are on top.
    • Long q arms are on the bottom.
    • Larger chromosomes have smaller numbers and numbers increase with diminishing size. 
  5. What is G banding?
    • Mild heat or enzymes that partially digest chromosomal proteins.
    • Exposed to Giemsa dye.
    • Banding patterns help distinguish similar chromosomes and dectection of structural changes. 
  6. What are the two primary ways that chromosomes can be altered?
    • Total amount of genetic material within a single chromosome can be increased or decreased.
    • Genetic material in one chromosome can be rearranged without affecting the total amount of genetic material. 
  7. What are the two ways genetic material can be lost or gained?
    • Deletion (deficiency): occurs when a segment of chromosome is lost.
    • Duplication: occurs when a section of a chromosomeis repeated compared to the normal parental chromosome. 
  8. What are the two types of deletions?
    • Terminal deficiency: single break, a piece without centromere is lost and degrades.
    • Interstitial deficiency: two breaks, central fragment is lost and two outer pieces reattach to each other.
  9. Cri-du-chat syndrome, Angelman & prader willi syndrome, Smith-Magenis Syndrome, are all examples of what?
  10. What do duplications normally occur from?
    Result from abnormal events during recombination. (unequal crossing over between homologous chromosomes and sister chromotids.
  11. What is a gene family and how are the formed?
    • Two or more genes that are similar to each other.
    • Accumulation of small chromosomal duplications can over the course of many generations. 
  12. What are homologous genes?
    Two or more genes derived from a single ancestral gene. 
  13. What is the difference between Paralogs and Orthologs?
    Homologous genes within a single species are paralogs; while homologous genes found in multiple species are called orthologs.
  14. How are paralogs and orthologs derrived?
    • Paralogs: result of duplications
    • Orthologs: result of speciation 
  15. What is the difference between pericentric and paracentric inversions?
    • Pericentric inversion: Centromere lies within the inverted region.
    • Paracentric inversion: Centromere is found outside the inverted region. 
  16. Why do most inversions have no phenotypic effects?
    The gene's promotor and coding sequence are maintained in the same direction, so transcription can still occur.
  17. What is a disorder is caused by a breakpoint in a vital gene due to inversion?
    Hemophilia (Type A) X linked inversion
  18. What is an Inversion Heterozygote?
    An individual with one normal and one inverted chromosome.
  19. What is an inversion loop?
    During meiosis 1, an inversion loop forms to permit the homologous genes on both chromosomes to align. 
  20. If crossing over takes place when a gene has a pericentic inversion, what happens?
    It leads to duplication/ deletion of genetic material.
  21. If crossing over takes place when a gene has a paracentric inversion, what happens?
    Formation of both Dicentric and Acentric chromosomes. This causes the dicentric chromosome to be pulled apart and the acentric chromosome to be lost or degraded.
  22. What is a translocation?
    One segment of a chromosome breaks off and becomes attached to a different chromosome.
  23. What are telomeres?
    ends of chromosomes containing tandemly repeating sequences. Their purpos is to preven the attachment of DNA to the ends of chromosomes.
  24. What are reactive ends and what are the consequences of having them?
    • Broken ends of chromsomes that lack telomeres.
    • DNA repair enzymes may join broken pieces of different chromosomes together to produce abnormal chromosomes. 
  25. What are the two types of nonhomologous crossing over?
    • Reciprocal translocation
    • Simple translocation 
  26. What is reciprocal translocation?
    produced when two non homologous chromosomes swap parts.
  27. What is a simple translocation?
    produced when a fragment from one chromosome is attached to andother chromosome (unbalanced).
  28. What is a What is an example of a simple translocation?
    Familial down syndrome.
  29. What is a Robertsonian translocation?
    A type of simple translocation where the centromeric region of two non homologous acrocentric chromosomes become fused to form a single chromosome.
  30. What is Euploidy?
    Having the total chromosome number that is exact multiple of a chromosome set.
  31. What is aneuploidy?
    Alteration in chromosome number so that the total number is not an exact multiple of a set.
  32. What is nondisjunction?
    Full segregation of chromosomes is not obtained. Either bivalents in Meiosis 1 or sister chromotids in Meiosis 2. 
  33. Down syndrome, edward syndrome, and patau syndrome are the result from what?
  34. What are two aneuploid condiditons in sex chromosomes?
    • Klinefelter (XXY)
    • Turner (XO) 
  35. What is endopolyploidy?
    • Variation in euploidy can be restricted to certain tissues.
    • The mechanism of formation is mitosis without cytokinesis. 
  36. What is a Chromocenter?
    Where all polytene chromosomes are attached. 
  37. What are the three natural ways chromosome composition can vary?
    • Meiotic nondisjunction
    • Mitotic nondisjunction
    • Autopolyploidy 
  38. What is autopolyploidy?
    An organism or part of an organism having more than two sets of chromosomes all derived from the same species.
  39. What is allopolyploidy?
    An organism with sets of chromosomes from two or more different species. Hybrids.
  40. What is allotetraploidy?
    Diploid for two genomes from a different species.
  41. What are homeologous chromosomes?
    Are evolutionarily related chromosomes from two different species that can properly synapse during meiosis to create haploid gametes. Fertile offspring.
  42. What are NonHomeologous chromosomes?
    Produce sterile offspring.
  43. What is a heterokaryon?
    A cell containing two nuclei. It will spontaneously go through nuclear fusion to create a hybrid cell with a single nucleus.
  44. What  is parthenogenesis?
    Inducement of egg to begin development without fertilization.
  45. What is an Anther culture (androgenesis)?
    A method of breading in order to selectively weed out recessive alleles of a plant.