Figure: 7.CO Title: Human Karyotype Caption: Spectral karyotyping of human chromosomes utilizing differentially labeled “painting” probes. (Evelin Schrock, Stan du Manoir, and Tom Reid, National Institutes of Health)

Figure: 7.1 Title: Nondisjunction Caption: Nondisjunction during the first and second meiotic divisions. In both cases, some of the gametes that are formed either contain two members of a specific chromosome or lack that chromosome. After fertilization by a gamete with a normal haploid content, monosomic, disomic (normal), or trisomic zygotes are produced.

Figure: 7.2 Title: Cri-du-chat Syndrome Caption: A representative karyotype and a photograph of a child exhibiting cri-du-chat syndrome (46,5p–). In the karyotype, the arrow identifies the absence of a small piece of the short arm of one member of the chromosome 5 homologs. (Photo: Courtesy of the Greenwood Genetic Center, Greenwood, SC)

Figure: 7.3 Title: Down Syndrome Karyotype Caption: In the karyotype, three members of the G-group chromosome 21 are present, creating the 47,21+ condition. (Photo: Courtesy of the Greenwood Genetic Center, Greenwood, SC)

Figure: 7.4 Title: Incidence of Down Syndrome Births Caption: Incidence of Down syndrome births related to maternal age.

Figure: 7.5b Title: Patau Syndrome Caption: The karyotype and phenotypic depiction of an infant with Patau syndrome, where three members of the D-group chromosome 13 are present, creating the 47,13+ condition.

Figure: 7.6 Title: Autopolyploid Versus Allopolyploid Caption: Contrasting chromosome origins of an autopolyploid versus an allopolyploid karyotype.

Figure: 7.7 Title: Involvement of Colchicine Caption: The potential involvement of colchicine in doubling the chromosome number. Two pairs of homologous chromosomes are shown. While each chromosome had replicated its DNA earlier during interphase, the chromosomes do not appear as double structures until late prophase. When anaphase fails to occur normally, the chromosome number doubles if the cell reenters interphase.

Figure: 7.8 Title: The Origin and Propagation of an Amphidiploid Caption: The origin and propagation of an amphidiploid. Species 1 contains genome A consisting of three distinct chromosomes, a1, a2 and a3. Species 2 contains genome B consisting of two distinct chromosomes, b1 and b2. Following fertilization between members of the two species and chromosome doubling, a fertile amphidiploid containing two complete diploid genomes (AABB) is formed.

Figure: 7.10 Title: Chromosomal Mutations Caption: An overview of the five different types of rearrangement of chromosome segments.

Figure: 7.11 Title: Terminal and Intercalary Deletions Caption: Origins of (a) a terminal and (b) an intercalary deletion. In (c), pairing occurs between a normal chromosome and one with an intercalary deletion by looping out the undeleted portion to form a deletion (or compensation) loop.

Figure: 7.12 Title: Duplicated and Deficient Regions of Chromosomes Caption: The origin of duplicated and deficient regions of chromosomes as a result of unequal crossing over. The tetrad on the left is mispaired during synapsis. A single crossover between chromatids 2 and 3 results in the deficient (chromosome 2) and duplicated (chromosome 3) chromosomal regions shown on the right. The two chromosomes uninvolved in the crossover event remain normal in gene sequence and content.

Figure: 7.13ab Title: Bar Eye Phenotype in Drosophila Caption: The duplication genotypes and resultant Bar eye phenotypes in Drosophila. Photographs show two Bar eye phenotypes and the wild type(B+/B+). (Photos: Mary Lilly/Carnegie Institution of Washington)

Figure: 7.14 Title: Pericentric Inversion Caption: One possible origin of a pericentric inversion.

Figure: 7.15a Title: Single Crossover within an Inversion Loop Caption: The effects of a single crossover within an inversion loop in (a) a paracentric inversion, where two altered chromosomes are produced: one acentric and one dicentric. Both chromosomes also contain duplicated and deficient regions. The effects of this crossover in (b), a pericentric inversion, produces two altered chromosomes, both with duplicated and deficient regions.

Figure: 7.15b Title: Single Crossover within an Inversion Loop Caption: The effects of a single crossover within an inversion loop in (a) a paracentric inversion, where two altered chromosomes are produced: one acentric and one dicentric. Both chromosomes also contain duplicated and deficient regions. The effects of this crossover in (b), a pericentric inversion, produces two altered chromosomes, both with duplicated and deficient regions.

Figure: 7.16ab Title: Translocation Caption: (a) Possible origin of a reciprocal translocation. (b) Synaptic configuration formed during meiosis in an individual that is heterozygous for the translocation.

Figure: 7.16c Title: Translocation Caption: (c) Two possible segregation patterns, one of which leads to a normal and a balanced gamete (called alternate segregation) and one that leads to gametes containing duplications and deficiencies (called adjacent segregation).

Figure: 7.17 Title: Translocation in Familial Down Syndrome Caption: Chromosomal involvement and translocation in familial Down syndrome. The photograph shows the relevant chromosomes from a trisomy 21 offspring produced by a translocation carrier parent. (Photo: Dr. Jorge Yunis)

Figure: 7.UN1 Title: Insights and Solutions Caption: A male Drosophila from a wild-type stock is discovered to have only seven chromosomes, whereas normally 2n = 8. Close examination reveals that one member of chromosome IV (the smallest chromosome) is attached to (translocated to) the distal end of chromosome II and is missing its centromere, thus accounting for the reduction in chromosome number. (a) Diagram all members of chromosomes II and IV during synapsis in meiosis I.

Figure: 7.UN2 Title: Insights and Solutions Caption: A male Drosophila from a wild-type stock is discovered to have only seven chromosomes, whereas normally 2n = 8. Close examination reveals that one member of chromosome IV (the smallest chromosome) is attached to (translocated to) the distal end of chromosome II and is missing its centromere, thus accounting for the reduction in chromosome number. (b) If this male mates with a female with a normal chromosome composition who is homozygous for the recessive chromosome IV mutation eyeless (ey), what chromosome compositions will occur in the offspring regarding chromosomes II and IV?

Figure: 7.UN3 Title: Problems and Discussion Caption: Woman found to be heterozygous for a chromosomal rearrangement.