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Questions and Answers
What is the purpose of gel electrophoresis in DNA sequencing?
What is the purpose of gel electrophoresis in DNA sequencing?
- To translate DNA into proteins
- To separate DNA fragments based on their charge
- To replicate DNA fragments
- To separate DNA fragments based on their size (correct)
What is the main difference between the DNA arrangement in eukaryotes and prokaryotes?
What is the main difference between the DNA arrangement in eukaryotes and prokaryotes?
- The size of the genome
- The type of DNA molecule
- The number of chromosomes
- The presence of a well-defined nucleus (correct)
What is the approximate number of genes in the human genome?
What is the approximate number of genes in the human genome?
- 10,000
- 20,000 (correct)
- 40,000
- 30,000
What is the percentage of noncoding DNA in the human genome?
What is the percentage of noncoding DNA in the human genome?
What is the purpose of supercoiling in prokaryotes?
What is the purpose of supercoiling in prokaryotes?
What is unique about the marbled lungfish's genome?
What is unique about the marbled lungfish's genome?
What is the purine that always pairs with cytosine in DNA molecules?
What is the purine that always pairs with cytosine in DNA molecules?
Who determined the structure of DNA using Rosalind Franklin's X-ray crystallography image?
Who determined the structure of DNA using Rosalind Franklin's X-ray crystallography image?
What is the method of DNA sequencing developed by Fred Sanger?
What is the method of DNA sequencing developed by Fred Sanger?
What is the difference between deoxynucleotides and dideoxynucleotides?
What is the difference between deoxynucleotides and dideoxynucleotides?
What is the purpose of using a predetermined ratio of deoxynucleotides to dideoxynucleotides in DNA sequencing?
What is the purpose of using a predetermined ratio of deoxynucleotides to dideoxynucleotides in DNA sequencing?
Who was the person who contributed to the discovery of the shape of DNA but did not receive the Nobel Prize?
Who was the person who contributed to the discovery of the shape of DNA but did not receive the Nobel Prize?
What is the characteristic of the prokaryotic genome?
What is the characteristic of the prokaryotic genome?
What is the function of histones in eukaryotes?
What is the function of histones in eukaryotes?
What is the term for the tightly packaged region of eukaryotic chromosomes?
What is the term for the tightly packaged region of eukaryotic chromosomes?
What is the location of the prokaryotic chromosome?
What is the location of the prokaryotic chromosome?
What is the purpose of plasmids in prokaryotes?
What is the purpose of plasmids in prokaryotes?
What is the term for the less dense region of eukaryotic chromosomes?
What is the term for the less dense region of eukaryotic chromosomes?
What is the characteristic of euchromatin?
What is the characteristic of euchromatin?
What is the term for the process in which one parental DNA strand acts as a template for new DNA synthesis?
What is the term for the process in which one parental DNA strand acts as a template for new DNA synthesis?
What is the result of Meselson and Stahl's experiment after one round of cell division?
What is the result of Meselson and Stahl's experiment after one round of cell division?
What is the purpose of the Meselson and Stahl experiment?
What is the purpose of the Meselson and Stahl experiment?
What is the difference between the 15N and 14N DNA in the Meselson and Stahl experiment?
What is the difference between the 15N and 14N DNA in the Meselson and Stahl experiment?
What is the model of DNA replication supported by the Meselson and Stahl experiment?
What is the model of DNA replication supported by the Meselson and Stahl experiment?
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Study Notes
DNA Structure and Replication
- Complementary base pairing: Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C)
- Predicting DNA strand sequence: knowing the sequence of the complementary strand allows us to predict the sequence of the original strand
DNA Structure Discovery
- Rosalind Franklin's X-ray crystallography image of DNA led to Watson and Crick's discovery of the double helix structure in 1953
- Watson and Crick won the Nobel Prize in 1962, but Rosalind Franklin had passed away by then, likely due to radiation poisoning
DNA Sequencing
- Fred Sanger's dideoxy chain termination method is widely used for DNA sequencing, including the human genome sequencing project
- Method uses chain terminators (dideoxynucleotides) that lack a free 3' OH group, preventing further DNA strand extension
- Sanger's method generates DNA fragments of different sizes, which can be separated using gel electrophoresis
Gel Electrophoresis
- Technique used to separate DNA fragments based on size
- Nucleic acids are loaded into a gel matrix, and an electric current is applied to pull negatively charged molecules towards the positive electrode
- Smaller molecules move faster through the gel, separating fragments by size
DNA Packaging in Cells
- Prokaryotes (e.g., E. coli) have a single circular chromosome in the cytoplasm, condensed into the nucleoid
- Plasmids are small loops of DNA outside the genomic chromosome, not essential for normal growth and function
- Human genome consists of approximately 3.2 billion base pairs, with only 0.4% variation between individuals
DNA Arrangement in Prokaryotes and Eukaryotes
- Prokaryotes have a single circular chromosome, wound tightly around itself (supercoiling)
- Eukaryotes have linear DNA molecules wrapped around proteins (histones) to form nucleosomes, which are further compacted into fibers
DNA Replication
- Three models of DNA replication were proposed: conservative, semi-conservative, and dispersive
- Meselson and Stahl's experiment using E. coli grown in heavy nitrogen (15N) and 14N supported the semi-conservative replication model
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