Fig 6-1 Figure: 06-01a Caption: Results of gamete formation where two heterozygous genes are (a) on two different pairs of chromosomes

Fig 6-1 Figure: 06-01b Caption: Results of gamete formation where two heterozygous genes are (b) on the same pair of homologs, but where no exchange occurs between them.

Fig 6-1 Figure: 06-01c Caption: Results of gamete formation where two heterozygous genes are (c) on the same pair of homologs, where an exchange occurs between two nonsister chromatids.

Fig 6-2 Figure: 06-02a Caption: Results of a cross involving two genes located on the same chromosome where complete linkage is demonstrated. (a) The  results of the cross.

Fig 6-2 Figure: 06-02b Caption: Results of a cross involving two genes located on the same chromosome where complete linkage is demonstrated. (b) The results of a test cross involving the  progeny.

Fig 6-3 Figure: 06-03a Caption: The F1 and F2 results of crosses involving the yellow-body, white-eye mutations and the white-eye, miniature-wing mutations. In cross A, 1.3 percent of the F2 flies (males and females) demonstrate recombinant phenotypes, which express either white or yellow. In cross B, 37.2 percent of the  flies (males and females) demonstrate recombinant phenotypes, which are either miniature or white mutants.

Figure: 06-03b Caption: The  and  results of crosses involving the yellow-body, white-eye mutations and the white-eye, miniature-wing mutations. In cross A, 1.3 percent of the  flies (males and females) demonstrate recombinant phenotypes, which express either white or yellow. In cross B, 37.2 percent of the  flies (males and females) demonstrate recombinant phenotypes, which are either miniature or white mutants.

Fig 6-4 Figure: 06-04 Caption: A map of the yellow (y), white (w), and miniature (m) genes on the X chromosome of Drosophila melanogaster. Each number represents the percentage of recombinant offspring produced in one of three crosses, each involving two different genes.

Fig 6-5 Figure: 06-05a Caption: An example of a single crossover between two nonsister chromatids and the gametes subsequently produced. In (a) the exchange does not alter the linkage arrangement between the alleles of the two genes, only parental gametes are formed, and the exchange goes undetected.

Fig 6-5 Figure: 06-05b Caption: An example of a single crossover between two nonsister chromatids and the gametes subsequently produced. In (b), the exchange separates the alleles and results in recombinant gametes, which are detectable.

Fig 6-6 Figure: 06-06 Caption: The consequences of a single exchange between two nonsister chromatids occurring in the tetrad stage. Two noncrossover (parental) and two crossover (recombinant) gametes are produced.

Fig 6-7 Figure: 06-07 Caption: Consequences of a double exchange occurring between two nonsister chromatids. Because the exchanges involve only two chromatids, two noncrossover gametes and two double-crossover gametes are produced. The photograph illustrates several chiasmata found in a tetrad isolated during the first meiotic prophase stage.

Fig 6-8 Figure: 06-08a Caption: A three-point mapping cross involving the yellow 1y or y+2, white 1w or w+2, and echinus 1ec or ec+2  genes in Drosophila melanogaster. NCO, SCO, and DCO refer to noncrossover, single-crossover, and double-crossover groups, respectively. Because of the complexity of this and several of the ensuing figures, centromeres have not been included on the chromosomes, and only two nonsister chromatids are initially shown in the left-hand column.

Fig 6-8 Figure: 06-08b Caption: A three-point mapping cross involving the yellow 1y or y+2, white 1w or w+2, and echinus 1ec or ec+2  genes in Drosophila melanogaster. NCO, SCO, and DCO refer to noncrossover, single-crossover, and double-crossover groups, respectively. Because of the complexity of this and several of the ensuing figures, centromeres have not been included on the chromosomes, and only two nonsister chromatids are initially shown in the left-hand column.

Fig 6-9 Figure: 06-09 Caption: The three possible sequences of the white, yellow, and echinus genes, the results of a double crossover in each case, and the resulting phenotypes produced in a test cross. For simplicity, the two noncrossover chromatids of each tetrad are omitted.

Fig 6-10 Figure: 06-10a Caption: (a) Some possible allele arrangements and gene sequences in a heterozygous female.

Figure: 06-10b Caption: The data from a three-point mapping cross, depicted in (b), where the female is test crossed, provide the basis for determining which combination of arrangement and sequence is correct. [See Figure 6–11 (d).]

Fig 6-11 Figure: 06-11 Caption: Producing a map of the three genes in the cross in Figure 6-10, where neither the arrangement of alleles nor the sequence of genes in the heterozygous female parent is known.

Fig 6-12 Figure: 06-12 Caption: Three types of double exchanges that may occur between two genes. Two of them, (b) and (c), involve more than two chromatids. In each case, the detectable recombinant chromatids are bracketed.

Fig 6-13 Figure: 06-13 Caption: The relationship between the percentage of recombinant chromatids that occur and actual map distance when (a) Poisson distribution is used to predict the frequency of recombination in relation to map distance; and (b) there is a direct relationship between recombination and map distance.

Figure: 06-14 Caption: A partial genetic map of the four chromosomes of Drosophila melanogaster. The circle on each chromosome represents the position of the centromere.

Fig 6-16 Figure: 06-16 Caption: The production of mutant tissue in a female Drosophila heterozygous for the recessive yellow (y) and singed (sn) alleles as a result of mitotic recombination.

Fig 6-23 Figure: 06-23 Caption: A hypothetical grid of data used in synteny testing to assign genes to their appropriate human chromosomes. Three somatic hybrid cell lines, designated 23, 34, and 41, have each been scored for the presence, or absence, of human chromosomes 1–8, as well as for their ability to produce the hypothetical human gene products A, B, C, and D.

Fig 6-24 Figure: 06-24 Caption: Representative regional gene assignments for human chromosome 1 and the X chromosome. Many assignments were initially derived by using somatic cell hybridization techniques.