Chapter 8
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37 terms
Terms | Definitions |
|---|---|
 Chromosome Mutations or Chromosome Aberrations | Changes in the total number of chromosome, such as a deletion or rearrangement |
| Aneuploidy | Variations in chromosome number. When an organism gains or loses one ore more chromosomes and has other than an exact multiple of the haploid set |
| Euploidy | Completely haploid sets of chromosomes are present |
| Polyploidy | Occurs when more than two sets of chromosomes are present |
| Nondisjunction | Chromosomal variation arises from nondisjunction, where chromosomes or chromatids fail to disjoin and move to opposite poles during Meiosis I or II |
| Monosomy | The loss of one chromosome to produce a 2n-1 complement |
| Trisomy | 2n+1 Chromosomes. Often lethal for autosomes, but not sex chromosomes. Three copies of one chromosome are present so pairings are irregular. |
| Trivalent | When three copies of a chromosome are synapsed |
| Univalent | An unpaired chromosome, can be present along with a bivalent instead of a trivalent. When 3 chromosomes aren't synapsed, instead 2 are and 1 is left unpaired. |
| Down Syndrome | Results from trisomy of chromosome 21 |
| Familial Down Syndrome | Runs in families, involve a translocation of chromosome 21 |
| Amniocentesis or Chorionic Villus Sampling (CVS) | Testings for women who become pregnant late in their reproductive years |
| Patau Syndrome | Trisomy 13 |
| Edwards Syndrome | Trisomy 18 |
| Triploid | 3n |
| Tetraploid | 4n |
| Pentaploid | 5n |
| Autopolyploidy | The addition of one or more sets of chromosomes identical to the haploid complement of the same species |
| Allopolyploidy | The combination of chromosome sets from different species as a consequence of interspecific matings |
| Allotetraploid | Arises from hybridization of two closely related species |
| Endopolyploidy | The condition in which only certain cells in an otherwise diploid organism are polyploid |
| Deletion (deficiency) | Chromosome breaks in one or more places and a portion if it is lost, the missing piece. |
| Terminal Deletion | Deletion near one end |
| Intercalary Deletion | Deletion from the interior of the chromosome |
| Cri-du-chat | Results form a segmental deletion of a small terminal portion of the short arm of chromosome 5 |
| Duplications | Arise as the result of unequal crossing over during meiosis or through a replication error prior to meiosis |
| Gene Redundancy | ORganisms that have multiple copies of ribosomal RNA genes (rRNA) |
| Gene Amplification | A mechanism to increase the rRNA |
| Inversion | Involves a rearrangement of the linear gene sequence rather than the loss of genetic information. Segment turned 180 degrees in a chromosome, requires two breaks and reinsertion of the inverted segment. May arise from chromosomal looping |
| Paracentric inversion | Does not change the relative lengths of the two arms of a chromosome |
| Pericentric Inversion | Includes centromere, does change the relative lengths of the two arms of a chromosome |
| Paracentric inversion crossover | One recombinant chromatid is dicentric (two centromeres) and one is acentric (lacking a centromere) |
| Translocation | Movement of a chromosomal segment to a new location in the genome |
| Reciprocal Translocation | Involves the exchange of segments between two nonhomologous chromosomes. Unusual synapsis |
| Alternate Segregation | Leads to normal and a balanced gamete |
| Adjacent Segregation | Leads to gametes containing duplications and deficiencies |
| Fragile Sites | more susceptible to chromosome breakage when cells are cultured in the absence of certain chemicals such as folic acid |
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