PLB 113 Homework__2_KEY_Spring_2009_1_

PLB 113 Homework__2_KEY_Spring_2009_1_ - PLANT BIOLOGY 113...

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PLANT BIOLOGY 113 Spring 2009 Instructor: Professor S. O’Neill HOMEWORK QUESTIONS #2 (50 points) Please turn-in during lecture or to your discussion section by Thursday, April 30th. 1. What information can nucleotide sequencing of genomic DNA provide about the number of genes expressed in a plant? There are programs that will predict the position of genes in genomic DNA sequences. If cDNA sequence or ESTs are known, this information can also be used to locate genes. If the entire sequence of a genome is known, it is possible to predict the number of potential genes in a plant. However, this number does not indicate the number of genes expressed. Expressed genes encode gene products, and it is not known if these predicted genes are functional. 2. What is leaf mDNA? How is it prepared? When used in saturation hybridization experiments, what can it tell you about mRNA populations in a root? Leaf mDNA represents single stranded, single copy DNA that hybridizes specifically with leaf mRNAs. Single copy DNA is hybridized with an excess of leaf mRNA. Using a hydroxyapatite column, double stranded nucleic acids (which are bound to the column) are separated from single stranded nucleic acids (which are not bound to the column). RNA is hydrolyzed from all samples. The scDNA that was bound to the column is leaf mDNA, and the unbound scDNA is leaf null mDNA. Root mRNAs that hybridize with leaf mDNA are present in both leaves and roots. Therefore, leaf mDNA identifies mRNAs that are shared between leaves and roots. 3.
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PLB 113 Homework__2_KEY_Spring_2009_1_ - PLANT BIOLOGY 113...

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