Inversions may cause a variety of structural changes in the DNA Break points between genes Normal sequence B 5" 3 5 Breaks in DNA 3'5 O 5 3-D 5' 3'5'O 5' 3' O P 3' Inverted alignment B P D 3'5 D 5' 3'-O 5 3'5 3 -5' 3 5 P. Joining of breaks to complete inversion 5" 3" Inversion One break point between genes One within gene C (C disrupted) "C" P B "C" 3 Inversion Break points in genes A and D Creating gene fusions A DP 3 Inversion points of the inversion are clearly not in essential regions. Some of the possible consequences of inversion at the DNA level are shown in Figure 17-26. Most analyses of inversions are carried out on diploid cells that contain one normal chromosome set plus one set carrying the inversion. This type of cell is called an inversion heterozygote, but note that this designation does not imply that any gene locus is heterozygous; rather, it means that one normal and one abnormal chromosome set are present. The location of the inverted segment can often be detected microscopically. In meiosis, one chromosome twists once at the ends of the inversion to pair with its untwisted homolog; in this way, the paired homologs form a visible inversion loop (Figure 17-27). FIGURE 17-26 An inversion may have no effect on genes, may disrupt a gene, or may fuse parts of two genes, depending on the location of the break point. Genes are represented by A, B, C, and D. Template strand is dark green; nontemplate strand is light green; jagged red lines indicate where breaks in the DNA produced gene fusions (A with D) after inversion and rejoining. The letter P stands for promoter; arrows indicate the positions of the break points. o in D.
Inversions may cause a variety of structural changes in the DNA Break points between genes Normal sequence B 5" 3 5 Breaks in DNA 3'5 O 5 3-D 5' 3'5'O 5' 3' O P 3' Inverted alignment B P D 3'5 D 5' 3'-O 5 3'5 3 -5' 3 5 P. Joining of breaks to complete inversion 5" 3" Inversion One break point between genes One within gene C (C disrupted) "C" P B "C" 3 Inversion Break points in genes A and D Creating gene fusions A DP 3 Inversion points of the inversion are clearly not in essential regions. Some of the possible consequences of inversion at the DNA level are shown in Figure 17-26. Most analyses of inversions are carried out on diploid cells that contain one normal chromosome set plus one set carrying the inversion. This type of cell is called an inversion heterozygote, but note that this designation does not imply that any gene locus is heterozygous; rather, it means that one normal and one abnormal chromosome set are present. The location of the inverted segment can often be detected microscopically. In meiosis, one chromosome twists once at the ends of the inversion to pair with its untwisted homolog; in this way, the paired homologs form a visible inversion loop (Figure 17-27). FIGURE 17-26 An inversion may have no effect on genes, may disrupt a gene, or may fuse parts of two genes, depending on the location of the break point. Genes are represented by A, B, C, and D. Template strand is dark green; nontemplate strand is light green; jagged red lines indicate where breaks in the DNA produced gene fusions (A with D) after inversion and rejoining. The letter P stands for promoter; arrows indicate the positions of the break points. o in D.
Biology: The Dynamic Science (MindTap Course List)
4th Edition
ISBN:9781305389892
Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan
Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan
Chapter14: Dna Structure And Replication
Section: Chapter Questions
Problem 16TYK
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Question
In Figure 17-26, the bottom panel shows that genes B and
C are oriented in a different direction (note the promoters). Do you think this difference in orientation would
affect their functionality?
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