Chapter 5 Answers - Bio2600: Introduction to Cell Biology...

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Bio2600: Introduction to Cell Biology Study Guide Chapter 5 Answers 5-3 (a)—6; (b)—3; (c)—2; (d)—5; (e)—1; (f)—4 5-4 A. Adenine and guanine are purines; cytosine and thymine are pyrimidines. B. Cytosine pairs with guanine and adenine with thymine. 5-5 See Figure A5-5 Figure A5-5 5-6 A. See Figure A5-6. Figure A5-6
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B. There are approximately 10 base pairs per turn when the DNA has the standard conformation. 5-7 5 CTACCCACGAATGC 3 . 5-8 D. 5 -AAGCGCTT-3 3 -TTCGCGAA-5 None of the other sequences will base-pair with themselves. This double-stranded DNA molecule has the same sequence whether read forward or backward, which is why it is described as palindromic. Note that the reading direction is always defined as 5 to 3 . An example of a palindromic sentence is “Step on no pets.” 5-9 Choice (a) is the answer. Since the sequence of nucleotides in the DNAs from different species varies considerably, the ratio A-T to G-C base pairs will vary as well. Yet since A must always pair with T and G with C, the ratio of A+G to C+T must always be 1 (choice (b) is therefore incorrect). Choice (c) is incorrect, since the DNA backbone always contains a 1:1 ratio of sugar to phosphate. Choice (d) is incorrect, as all living organisms contain only A, G, C, and T in their DNA (but modifications of these bases occur in some organisms and under some circumstances, after their incorporation into the nucleotide chain). Choice (e) is incorrect because all genomic DNA is double stranded (except in some viruses). 5-13 In eucaryotic chromosomes, DNA is complexed with proteins to form chromatin . The paternal and maternal copies of human Chromosome 1 are homologous , whereas the paternal copy of Chromosome 1 and the maternal copy of Chromosome 3 are nonhomologous . Cytogeneticists can determine large-scale chromosomal abnormalities by looking at a patient’s karyotype . Fluorescent molecules can be used to paint a chromosome by virtue of DNA hybridization , and thereby to identify each chromosome using microscopy.
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This note was uploaded on 04/02/2008 for the course BIO 2600 taught by Professor Vanburkem during the Winter '08 term at Wayne State University.

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Chapter 5 Answers - Bio2600: Introduction to Cell Biology...

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