Fig 8-1 Figure: 08-01 Caption: Nondisjunction during the first and second meiotic divisions. In both cases, some of the gametes formed either contain two members of a specific chromosome or lack that chromosome. Following fertilization by a gamete with a normal haploid content, monosomic, disomic (normal), or trisomic zygotes are produced.

Fig 8-3 Figure: 08-03a Caption: Drawings of capsule phenotypes of the fruits of the Jimson weed Datura stramonium. In comparison with wild type, each phenotype is the result of trisomy of 1 of the 12 chromosomes characteristic of the haploid genome. The photograph illustrates the plant itself.

Fig 8-4 Figure: 08-04 Caption: Diagrammatic representation of one possible pairing arrangement during meiosis I of three copies of a single chromosome, forming a trivalent configuration. During anaphase I, two chromosomes move toward one pole and one chromosome toward the other pole.

Fig 8-6 Figure: 08-06 Caption: Incidence of Down syndrome births contrasted with maternal age.

Fig 8-9 Figure: 08-09 Caption: Contrasting chromosome origins of an autopolyploid versus an allopolyploid karyotype.

Fig 8-10 Figure: 08-10 Caption: The potential involvement of colchicine in doubling the chromosome number, as occurs during the production of an autotetraploid. Two pairs of homologous chromosomes are followed. While each chromosome has 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.

Fig 8-11 Figure: 08-11 Caption: The origin and propagation of an amphidiploid. Species 1 contains genome A consisting of three distinct chromosomes,  and  Species 2 contains genome B consisting of two distinct chromosomes,  and  Following fertilization between members of the two species and chromosome doubling, a fertile amphidiploid containing two complete diploid genomes (AABB) is formed.

Fig 8-13 Figure: 08-13 Caption: Application of the somatic cell hybridization technique in the production of an amphidiploid. Cells from the leaves of two species of plants are removed and cultured. The cell walls are digested away and the resultant protoplasts are induced to undergo cell fusion. The hybrid cell is selected and stimulated to divide and differentiate, as illustrated in the photograph. An amphidiploid has a complete set of chromosomes from each parental cell type and displays phenotypic characteristics of each. Two pairs of chromosomes from each species are depicted.

Fig 8-14 Figure: 08-14 Caption: Overview of the five different types of rearrangement of chromosome segments.

Fig 8-15 Figure: 08-15 Caption: Origins of (a) a terminal and (b) intercalary deletion. In part (c), pairing occurs between a normal chromosome and one with an intercalary deletion by looping out the undeleted portion to form a deficiency (or a compensation) loop.

Fig 8-16 Figure: 08-16 Caption: Deficiency loop formed in salivary chromosomes of Drosophila melanogaster where the fly is heterozygous for a deletion. The deletion encompasses bands 3C2 through 3C11, corresponding to the region associated with the Notch phenotype.

Fig 8-17 Figure: 08-17 Caption: The origin of duplicated and deficient regions of chromosomes as a result of unequal crossing over. The tetrad at the left is mispaired during synapsis. A single crossover between chromatids 2 and 3 results in deficient and duplicated chromosomal regions. (See chromosomes 2 and 3, respectively, on the right.) The two chromosomes uninvolved in the crossover event remain normal in their gene sequence and content.

Fig 8-18 Figure: 08-18a Caption: (a) The duplication genotypes and resultant Bar eye phenotypes in Drosophila. Photographs show two Bar eye phenotypes and the wild type (B+/B+).

Fig 8-19 Figure: 08-19 Caption: One possible origin of a pericentric inversion.

Fig 8-20 Figure: 08-20 Caption: A comparison of the arm ratios of a submetacentric chromosome before and after the occurrence of a paracentric and pericentric inversion. Only the pericentric inversion results in an alteration of the original ratio.

Fig 8-21 Figure: 08-21 Caption: Illustration of how synapsis occurs in a paracentric inversion heterozygote by virtue of the formation of an inversion loop.

Fig 8-22 Figure: 08-22a Caption: The effects of a single crossover within an inversion loop in cases involving (a) a paracentric inversion. In (a), two altered chromosomes are produced, one that is acentric and one that is dicentric. Both chromosomes also contain duplicated and deficient regions.

Fig 8-22 Figure: 08-22b Caption: The effects of a single crossover within an inversion loop in cases involving (b) a pericentric inversion. In (a), two altered chromosomes are produced, one that is acentric and one that is dicentric. Both chromosomes also contain duplicated and deficient regions.

Fig 8-23 Figure: 08-23ab Caption: (a) The possible origin of a reciprocal translocation; (b) the synaptic configuration formed during meiosis in an individual that is heterozygous for the translocation.

Fig 8-23 Figure: 08-23c 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).

Fig 8-24 Figure: 08-24 Caption: The possible origin of a Robertsonian translocation. Two independent breaks occur within the centromeric region on two nonhomologous chromosomes. Centric fusion of the long arms of the two acrocentric chromosomes creates the unique chromosome. Two acentric fragments remain.

Fig 8-25 Figure: 08-25 Caption: Chromosomal involvement in familial Down syndrome, as described in the text. The photograph illustrates the relevant chromosomes from a trisomy 21 offspring produced by a translocation carrier parent.

Figure: 08-UN01 Caption: a) Diagram all members of chromosomes II & IV during synapsis in Meiosis I

Figure: 08-UN02 Caption: (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: 08-UN04 Caption: one-half red-eyed females and one-half white-eyed males

Figure: 08-UN03 Caption: Woman found to be heterozygous for a chromosonal rearrangement