3. Double-stranded breaks are potentially lethal, unless they are repaired. 4. Repair systems in the cell correct the double-stranded breaks by joining bro- ken ends back together (see Chapter 16 for a detailed discussion of DNA repair). FIGURE 17-19 Each of the four types of chromosomal rearrangements can be produced by either of two basic mechanisms: chromosome breakage and rejoining or crossing over between repetitive DNA. Chromosome regions are numbered 1 through 10. Homologous 5. If the two ends of the same break are rejoined, the original DNA order is re- stored. If the ends of two different breaks are joined, however, one result is one or another type of chromosomal rearrangement. 6. The only chromosomal rearrangements that survive meiosis are those that produce DNA molecules that have one centromere and two telomeres. If a chromosomes are the same color. Origins of chromosomal rearrangements Breakage and rejoining Crossing over between repetitive DNA Deletion -3 2 Loss 32 4 Loss Deletion and duplication 3 4 23 23 4 Inversion ! 10 10 Translocation 10 6 2 Chromosome break - Joining of broken ends Repetitive DNA segments X Crossover
Genetic Recombination
Recombination is crucial to this process because it allows genes to be reassorted into diverse combinations. Genetic recombination is the process of combining genetic components from two different origins into a single unit. In prokaryotes, genetic recombination takes place by the unilateral transfer of deoxyribonucleic acid. It includes transduction, transformation, and conjugation. The genetic exchange occurring between homologous deoxyribonucleic acid sequences (DNA) from two different sources is termed general recombination. For this to happen, an identical sequence of the two recombining molecules is required. The process of genetic exchange which occurs in eukaryotes during sexual reproduction such as meiosis is an example of this type of genetic recombination.
Microbial Genetics
Genes are the functional units of heredity. They transfer characteristic information from parents to the offspring.
In Figure 17-19, is there any difference between the inversion products formed from breakage and those
formed from crossing over?
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