SolutionProblemSetH - Problem Set H 1. What is Chargaffs...

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BILD 1 – Problem Set H Answers - 1 - Problem Set H 1. What is Chargaff’s Rule? Chargaff's rules state that DNA from any cell of all organisms should have a 1:1 ratio of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine . This pattern is found in both strands of the DNA. 2. If a cell’s DNA contains 33% G, approximately what percentage of its DNA is composed of T? G= 33% C=33% (approximately) T= 17 % (approximately) A=17% (approximately) 3. Why does Thymine only form pair with Adenine but not Guanine or Cytosine? Thyamine has to bind to a pyrimidine: Adenine and Guanine are purines with two organic rings. Cytosine and thymine are pyrimidines with a single ring. Purines are twice as wide as Pyrimidines. Therefore a purine-purine base pair would be too wide compared to a Pyrimidine-Pyrimidine base pair; thus, not conferring to the observed structure of the double helix. Thyamine has to bind to a purine that can form hydrogen bonds with it. This purine is Adenine and only Adenine. 4. What three main classes of enzymes are involved in nucleotide excision repair? Nuclease, DNA polymerase, DNA ligase 5. How many leading strands and lagging strands are present in one replication bubble? 2 leading and 2 lagging strands 6. What are histones? Nucleosomes? Histones: Small proteins responsible for the first level of DNA packing in chromatin. They have positive charges that bind tightly to DNA’s negative charge. Nucleosome: The basic unit of DNA packing (resemble beads on a string). 7. Gene expression passes through what two main stages to code for a protein? a. Transcription (the synthesis of RNA under the direction of DNA). b. Translation (the synthesis of a polypeptide chain through translation of an mRNA base sequence to an amino acid sequences). 8.
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SolutionProblemSetH - Problem Set H 1. What is Chargaffs...

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