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Questions and Answers
What is the primary function of DNA?
What is the primary function of DNA?
- To produce energy for the cell
- To provide structural support to organelles
- To protect the cell from external damage
- To contain biological instructions for species (correct)
Which bases are considered purines in DNA?
Which bases are considered purines in DNA?
- Adenine and Cytosine
- Adenine and Guanine (correct)
- Cytosine and Thymine
- Thymine and Uracil
How is the structure of DNA characterized?
How is the structure of DNA characterized?
- Double-stranded helix with complementary bases (correct)
- Single-stranded with a simple backbone
- Single helix allowing easy access to bases
- Linear molecule without hydrogen bonds
What type of bond connects the bases in DNA?
What type of bond connects the bases in DNA?
What is supercoiling in DNA?
What is supercoiling in DNA?
Which pairing of bases in DNA is held together by two hydrogen bonds?
Which pairing of bases in DNA is held together by two hydrogen bonds?
How many base pairs are approximately present in each turn of the DNA helix?
How many base pairs are approximately present in each turn of the DNA helix?
What role do histones play in DNA structure?
What role do histones play in DNA structure?
What type of proteins are H2A and H2B classified as?
What type of proteins are H2A and H2B classified as?
How many base pairs typically occur per turn of the DNA helix?
How many base pairs typically occur per turn of the DNA helix?
What is the role of H1 in nucleosomes?
What is the role of H1 in nucleosomes?
What term describes the twisting of DNA that occurs when it is overwound?
What term describes the twisting of DNA that occurs when it is overwound?
Which type of topoisomerase cleaves one strand of the DNA double helix?
Which type of topoisomerase cleaves one strand of the DNA double helix?
What primary structural feature distinguishes eukaryotic DNA from prokaryotic DNA?
What primary structural feature distinguishes eukaryotic DNA from prokaryotic DNA?
Which of the following describes the conditions that lead to negative supertwisting?
Which of the following describes the conditions that lead to negative supertwisting?
In the context of DNA supercoiling, what is predominantly observed in prokaryotes?
In the context of DNA supercoiling, what is predominantly observed in prokaryotes?
What characteristic is unique to prokaryotic cells compared to eukaryotic cells?
What characteristic is unique to prokaryotic cells compared to eukaryotic cells?
What is the function of silencers in genetic regulation?
What is the function of silencers in genetic regulation?
Which of the following statements is true regarding mitochondrial DNA?
Which of the following statements is true regarding mitochondrial DNA?
Which enzyme is primarily responsible for the assembly of new DNA segments during replication?
Which enzyme is primarily responsible for the assembly of new DNA segments during replication?
What is the primary role of a TATA box in a gene sequence?
What is the primary role of a TATA box in a gene sequence?
What type of ploidy is commonly found in prokaryotic organisms?
What type of ploidy is commonly found in prokaryotic organisms?
During DNA replication, what is the first major step involved?
During DNA replication, what is the first major step involved?
Which of the following accurately describes ribosomes found in prokaryotes?
Which of the following accurately describes ribosomes found in prokaryotes?
What role do initiator proteins play in DNA replication?
What role do initiator proteins play in DNA replication?
How does helicase contribute to DNA replication?
How does helicase contribute to DNA replication?
What is the directionality of DNA polymerase during replication?
What is the directionality of DNA polymerase during replication?
What is the primary function of DNA polymerase I in prokaryotes?
What is the primary function of DNA polymerase I in prokaryotes?
Which statement about DNA polymerase III is true?
Which statement about DNA polymerase III is true?
What advantage does the 3'-exonuclease activity of DNA polymerase III provide?
What advantage does the 3'-exonuclease activity of DNA polymerase III provide?
What type of bonds do nucleases cleave in nucleic acids?
What type of bonds do nucleases cleave in nucleic acids?
What initial structure forms as DNA unwinds during replication?
What initial structure forms as DNA unwinds during replication?
What is the primary role of exonucleases?
What is the primary role of exonucleases?
How does DNA polymerase III proofread its newly synthesized DNA?
How does DNA polymerase III proofread its newly synthesized DNA?
Why is the synthesis of the lagging strand discontinuous?
Why is the synthesis of the lagging strand discontinuous?
What is the function of RNA primers in DNA replication?
What is the function of RNA primers in DNA replication?
How is energy derived for the action of DNA ligase in bacteria?
How is energy derived for the action of DNA ligase in bacteria?
What structure is responsible for linking the phosphorylated 5′ terminus of one Okazaki fragment to the free 3′ terminus of another?
What structure is responsible for linking the phosphorylated 5′ terminus of one Okazaki fragment to the free 3′ terminus of another?
What type of supercoiling occurs in front of the helicase during DNA replication?
What type of supercoiling occurs in front of the helicase during DNA replication?
Which site on DNA polymerase III is responsible for polymerase activity?
Which site on DNA polymerase III is responsible for polymerase activity?
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Study Notes
DNA Function
- DNA contains the genetic instructions for an organism, determining traits and functions.
- DNA is passed down from parent to offspring.
- The sequence of DNA bases forms genes, responsible for protein synthesis.
DNA Structure
- DNA structure consists of a double helix with two antiparallel strands.
- The backbone of each strand is composed of alternating phosphate and deoxyribose sugar molecules linked by phosphodiester bonds.
- The four bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).
- A pairs with T, while G pairs with C through hydrogen bonds.
- The double helix has two grooves, a major groove and a minor groove.
DNA Supercoiling
- Supercoiling is a process that compacts DNA.
- Negative supercoiling is predominant in most cellular DNA, making it easier to unwind.
- Topoisomerases regulate supercoiling, Type I relaxes negative supercoiling, and Type II relaxes positive supercoiling.
DNA Replication
- DNA replication is a semi-conservative process.
- DNA replication involves three major steps: unwinding of the double helix, priming, and assembly of a new DNA segment.
- The process is initiated by initiator proteins binding to origin of replication, followed by helicase unwinding the DNA.
- DNA primase adds RNA primers to initiate new DNA synthesis.
- DNA polymerase III synthesizes new DNA strands in the 5' to 3' direction.
- DNA polymerase III has exonuclease activity for proofreading.
- Leading strand is synthesized continuously, while the lagging strand is synthesized in fragments called Okazaki fragments.
- DNA ligase joins Okazaki fragments together.
Eukaryotic DNA
- Eukaryotic DNA is packaged around histone proteins to form nucleosomes.
- Nucleosomes are further compacted into 30nm fibers and then higher-order structures.
- Non-histone proteins assist in further compaction.
Prokaryotic DNA
- Prokaryotes have a single circular chromosome.
- Prokaryotic DNA is less complex than eukaryotic DNA.
Mitochondrial DNA
- Mitochondria contain their own DNA, separate from the nuclear DNA.
- Mitochondrial DNA is circular and relatively small, encoding for specific proteins.
- Each mitochondrion contains 5-10 copies of its own genome.
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