Chapter 10 1. Outline the history of our knowledge on DNA up to Watson and Crick

Question

Chapter 10

1.Outline the history of our knowledge on DNA up to Watson and Crick. What were the main contributions made by each researcher’s key experiment?

2.Explain the setup of the Hershey and Chase experiment, what would the results have been if protein was the genetic material?

3.Draw the structure of a DNA nucleotide, labeling each main component correctly. How does an RNA nucleotide differ?

4.If a section of double stranded DNA contains 19% Adenine, how much Thymine is present?

5.You are a researcher studying the genetic basis of heart attacks and have been working to determine the expression levels of different genes that might contribute to cancer formation. You obtain the DNA methylation status of five genes of interest (the data are shown in the table below). The plus (+) sign indicates the level of DNA methylation; more plus signs correlates with increased methylation levels.Based on this information which genes would you predict to have the highest rate of transcription?

Gene

Methylation levels

1

++

2

+++++

3

+++

4

++

5

+

What are the characteristics of the 3 main DNA forms?

Chapter 11

What are the different types of chromatin?

What are the structures and important roles for telomeres and centromeres?

What are the differences found between eukaryotic chromosomes and mitochondrial?

Chapter 12

Explain each of the different models of replication.

If you grow a culture of bacteria in media with radioactive nucleotides so that all DNA in the cells include radioactive nucleotides and then place the bacteria in new non radioactive media. After two rounds of replication what proportion of the DNA molecules will contain radioactivity?

Summarize the similarities and differences between rolling-circle replication, theta replication and linear eukaryotic replication.

What are the functions of the different DNA polymerases found in eukaryotic cells?

Draw a replication fork and include all key components and orientations. (Leading/lagging strands, DNA helicase, RNA primer and DNA gyrase)

What is the Holliday model of recombination and what are the necessary steps?

Chapter 13

What are the different types of RNA and what roles do they play?

Describe the properties and functions of each of the RNA polymerases and how they differ depending on the organism.

Describe in detail the process and mechanisms of transcription in both prokaryotes and eukaryotes.

Chapter 14

What are the primary purposes of each of the three post transcriptional modifications that occur in eukaryotic cells.

What is alternative splicing and what role does it play in the cell?

How is ribosomal RNA processed after transcription?

How do siRNA and miRNA work, describe/draw out the process in detail.

Gene

Methylation levels

1

++

2

+++++

3

+++

4

++

5

+

Explanation / Answer

Answer: Chapter 10: Question No.1

In 1962 Watson (b. 1928), Crick (1916–2004), and Wilkins (1916–2004) jointly received the Nobel Prize in Physiology or Medicine for their 1953 determination of the structure of deoxyribonucleic acid (DNA). Wilkins’s colleague Franklin (1920–1958), who died from cancer at the age of 37, was not so honored.

Rosalind Franklin: In 1951, she works on X-ray crystallography of DNA.

Maurice Wilkins: It was Wilkins’s idea to study DNA by X-ray crystallographic techniques, which he had already begun to implement when Franklin was appointed by Randall.

James Watson and Francis Crick: At a conference in the spring of 1951 at the Zoological Station at Naples, Watson heard Wilkins talk on the molecular structure of DNA and saw his recent X-ray crystallographic photographs of DNA. Watson soon moved to the Cavendish Laboratory, where several important X-ray crystallographic projects were in progress. Here, Watson works with Crick, another physicist in biology, was supposed to be writing a dissertation on the X-ray crystallography of hemoglobin. Watson and Crick rapidly put together several models of DNA and attempted to incorporate all the evidence they could gather. Franklin’s excellent X-ray photographs, to which they had gained access without her permission, were critical to the correct solution. The four scientists announced the structure of DNA in articles that appeared together in the same issue of Nature.

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