Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

[Q]: Context: Comet ISON, formally known as C/2012 S1, was a sungrazing comet discovered on 21 September 2012 by Vitali Nevski ( , Vitebsk, Belarus) and Artyom Novichonok ( , Kondopoga, Russia). 
 Question: By whom was Comet ISON discovered?
[A]: artyom novichonok


[Q]: Context: A rock is a naturally formed, non-living Earth material. Rocks are made of collections of mineral grains that are held together in a firm, solid mass (Figure 1.1). How is a rock different from a mineral? Rocks are made of minerals. The mineral grains in a rock may be so tiny that you can only see them with a microscope, or they may be as big as your fingernail or even your finger (Figure Rocks are identified primarily by the minerals they contain and by their texture. Each type of rock has a distinctive set of minerals. A rock may be made of grains of all one mineral type, such as quartzite. Much more commonly, rocks are made of a mixture of different minerals. Texture is a description of the size, shape, and arrangement of mineral grains. Are the two samples in Figure 1.3 the same rock type? Do they have the same minerals? The same texture? The different colors and textures seen in this rock are caused by the presence of different minerals. A pegmatite from South Dakota with crystals of lepidolite, tourmaline, and quartz (1 cm scale on the upper left). Sample 2 Crystals are tiny or microscopic Magma erupted and cooled quickly Andesite As seen in Table 1.1, these two rocks have the same chemical composition and contain mostly the same minerals, but they do not have the same texture. Sample 1 has visible mineral grains, but Sample 2 has very tiny or invisible grains. The two different textures indicate different histories. Sample 1 is a diorite, a rock that cooled slowly from magma (molten rock) underground. Sample 2 is an andesite, a rock that cooled rapidly from a very similar magma that erupted onto Earths surface. A few rocks are not made of minerals because the material they are made of does not fit the definition of a mineral. Coal, for example, is made of organic material, which is not a mineral. Can you think of other rocks that are not made of minerals? Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: 
 Question: _______________________ is a naturally formed, non-living earth material.
[A]: rock


[Q]: Context: It has been previously shown that disruption of RAD26 in yeast strain W303-1B results in a strain that is deficient in transcription-coupled repair (TCR), the preferential repair of the transcribed strand of an expressed gene over the non-transcribed strand and the rest of the genome. RAD26 encodes a protein that is homologous to Cockayne syndrome group B protein (CSB) and is a member of the SWI2/SNF2 family of DNA-dependent ATPases involved in chromatin remodeling. Like the rad26 mutant, cells from Cockayne syndrome patients are defective in TCR. We examined the role of Rad26 in TCR by disrupting RAD26 in two repair-proficient laboratory strains and, remarkably, observed no effect upon TCR. Our results indicate that disruption of RAD26 alone is insufficient to impair TCR. Thus, W303-1B must already possess a mutation that, together with disruption of RAD26, causes a deficiency in TCR. We suggest that other genes are mutated in Cockayne syndrome cells that contribute to the deficiency in TCR. Surprisingly, deletion of RAD26 results in expression of genes that are repressed by flanking transposon delta elements, an Spt(-) phenotype. The delta elements appear to perturb local chromatin structure. Expression of genes flanked by delta elements in rad26Delta mutants is consistent with a role for Rad26 in chromatin remodeling. 
 Question: Which gene strand is targeted by transcription-coupled repair (TCR)?
[A]:
the transcribed strand