Concept explainers
Newsdate: March 1, 2030. A unique creature has been discovered during exploration of outer space. Recently, its genetic material has been isolated and analyzed. This material is similar in some ways to DNA in its chemical makeup. It contains in abundance the 4-carbon sugar erythrose and a molar equivalent of phosphate groups. In addition, it contains six nitrogenous bases: adenine (A), guanine (G), thymine (T), cytosine (C), hypoxanthine (H), and xanthine (X). These bases exist in the following relative proportions:
X-ray diffraction studies have established a regularity in the molecule and a constant diameter of about 30 Å. Together, these data have suggested a model for the structure of this molecule.
- (a) Propose a general model of this molecule. Describe it briefly.
- (b) What base-pairing properties must exist for H and for X in the model?
- (c) Given the constant diameter of 30 Å, do you think that either (i) both H and X are purines or both pyrimidines, or (ii) one is a purine and one is a pyrimidine?
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Concepts of Genetics (11th Edition)
- Lactose sugar is hydrolyzed to produce two monosaccharides.(ii) Why can't we store Vitamin C in our bodies?The distinction between a nucleoside and nucleotide is explained in (iii).arrow_forwardThe following define nucleic acids EXCEPT A) They are polyionic molecules of high molecular weight composed of subunits or monomers called nucleosides. B) They are chainlike macromolecules that function in the storage and transfer of genetic information. C They are polynucleotides. They contain genes that encode for polypeptides and RNAS.arrow_forwardRNA differs from DNA in that: a) The ribose in RNA nucleotides contains fewer oxygen atoms than does deoxyribose DNA nucleotides. b) It is always single stranded and cannot form base pairs. c) It contains the nucleotide uracil, which pairs with thymine. d) It is single-stranded but can fold into a variety of structures, some of which are double-stranded. e) RNA can only be found in the cytoplasm whereas DNA can only be found in the nucleus.arrow_forward
- Section B: True / False The diagram shows an amino acid in L-configuration. NH, 1. H- CO,H CH,OH This sugar can be found in DNA. ҫнон он 2. но CH,OH 3. Base pairing can be found between two purines in DNA. The relation between the following two sugars is epimers. сно сно но C-OH HCOH OH но C-H HC он HC- он он он CH,OH CH,OHarrow_forwardIntramolecular ______ are responsible for formation of the most common three-dimensional shape in proteins, the alpha helix. a) van der waals forces b) hydrogen bonds c) covalent bonds d) ionic (electrostatic) interactionsarrow_forwardDehydration synthesis always results in the formation of which of the following? A.)Water B.)Amino acids C.)Proteins D.)Peptidesarrow_forward
- The human eye is a remarkable organ. It forms a high-resolution image by focusing light through a transparent lens made of living tissue. The lens is made up largely of proteins called crystallins. Where did they originate?arrow_forwardRNA differs from DNA in that the base _______________ is substituted for _______________. (a) adenine; uracil (b) uracil; thymine (c) guanine; uracil (d) cytosine; guanine (e) guanine; adeninearrow_forwardRNA molecules are more easily broken down than DNA at a high pH. This can be attributed to the fact that: RNA has a higher melting temperature than DNA. RNA contains uracil that helps break down the RNA, whereas DNA contains thymine. RNA is single stranded but DNA is double stranded. RNA is a smaller chain than DNA, which makes RNA easier to break apart than DNA. RNA contains an oxygen at the 2' carbon of its ribose sugar whereas DNA does not.arrow_forward
- You have discovered a new molecule in outer space. You have never seen this type of molecule before on Earth. You analyze the composition and discover that it is made of 28% carbon atoms, 24% oxygen atoms, and 48% hydrogen atoms. You immediately decide that it is not an alien protein or an alien nucleotide. Explain why you know that the molecule cannot be a protein or a nucleotide. Do you think that the molecule is an alien fatty acid or an alien carbohydrate? Explain your decision Will your molecule be hydrophilic or hydrophobic? Explain your answer considering polarity and electronegativityarrow_forwardRNA and DNA have the following characteristic in common. Both use the same four nitrogenous bases. None of the other answers are correct. Both commonly form double-stranded molecules in the cell. Both contain a sugar-phosphate backbone in their chains of nucleotides. Both use 2-deoxyribose sugars in their nucleotides.arrow_forwardIt is a pyrimidine derivative that does not form part of nucleic acids.... A) Thymine B) Cytosine C) Adeninearrow_forward
- Concepts of BiologyBiologyISBN:9781938168116Author:Samantha Fowler, Rebecca Roush, James WisePublisher:OpenStax College