ExamI-06 - Bio324MolecularBiologyExamIOctober10.2006

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Bio 324 Molecular Biology Exam I October 10. 2006 This exam is worth a total of 100 points 1. a. The basic building block of nucleic acids is the nucleotide. It is composed of three components, what are they? (3 pts.) phosphates, nitrogenous base (purine or pyrimidine), and ribose sugar b. There are two types of nucleic acids in cells, DNA and RNA. List three differences between the structure of DNA and RNA. (3 pts.) thyamine vs uracil deoxyribose vs ribose ds vs ss c. Nucleic acids can be reversibly denatured and renatured. What bonds are being broken and reformed? Give two methods to denature nucleic acids. (4 pts.) hydrogen, denatured by pH or heat d. The genomes of most organisms are composed of both introns and exons. i. Define these two terms. (2 pts.) Introns - sequences of genomic DNA that are not coding sequences in a Open reading frame Exons - sequences that are apart of the open reading frame ii. Can exons be located in the non-coding regions of mRNAs? (1 pt.) yes, but they are seen as introns because after that specific splice they were seen as an intron but in another splice they may be seen as an exon. iii. Exons represent what fraction of the human genome? (1 pt.) 1% iv. For a single gene, is the location of the introns and exons in the RNA always invari- ant? Explain your answer. (3 pts.)
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2. a. The size of genomes is roughly proportional to the complexity of the organism until you reach higher eukaryotes. The largest variation in genome size within phyla is in in- sect and amphibian species. What accounts for the large variation in genome size between two amphibia that look nearly the same? (2 pts.) The amount of repetitive DNA. The higher eukaryotes have a greater amount of DNA due to an excess of repetitive DNA and a very low amount of unique DNA b. The largest fraction of the human genome is composed of transposons (45%). Are they an example of repetitive or non-repetitive DNA? What property do transposons possess? ( 3 pts.) c. There is a fair amount of disagreement about the actual number of genes within the human genome, ranging from estimates of 23,000 up to 40,000 genes, hardly much more than fruit flies (15,000) and round worms (19,000). When inspecting the se- quences of genomes, scientists try to identify ORFs (open reading frames) as being parts of functional genes. What is an ORF? (4 pts.) The open reading frame is the sequence of exons that code for a protein or function. It is the sequence between the start and stop codons.
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This note was uploaded on 01/26/2009 for the course BIOLOGY 244 taught by Professor Palter during the Fall '05 term at Temple.

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ExamI-06 - Bio324MolecularBiologyExamIOctober10.2006

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