70 Questions
What is the enzyme responsible for adding more repeating bases to the end of the lagging strand of telomeres?
Telomerase
In somatic cells, what is the consequence of lacking telomerase?
Progressive shortening of chromosomes
What is the average error rate of DNA replication?
Less than one mistake per billion bases
Which enzyme can proofread its work by checking the match between paired bases and correcting mismatched bases?
DNA polymerase
What occurs during mismatch repair in DNA replication?
Recognition and correction of mismatched bases after DNA synthesis
What type of damage can UV light cause to DNA?
Formation of thymine dimers
Which disease is characterized by the inability to repair DNA damaged by ultraviolet radiation?
Xeroderma Pigmentosum (XP)
What is the consequence of defects in DNA repair genes?
Increased susceptibility to cancer
What is the function of the nucleotide excision repair system?
Recognition and repair of specific types of DNA damage
What is the role of telomeres in limiting the amount of time cells remain in an actively growing state?
Contributing to chromosome shortening
Which enzyme is responsible for repairing damages to DNA and fixing mistakes in DNA synthesis?
DNA repair polymerase
What is the direction of DNA synthesis?
5' -> 3'
Which component of DNA forms the molecule's backbone?
Sugar and phosphate groups
What is the function of DNA ligase in DNA replication?
Joins Okazaki fragments on the lagging strand
Which bases form complementary pairs in DNA?
Adenine-Thymine, Guanine-Cytosine
What is the primary structure of DNA composed of?
Sugar and phosphate groups, nitrogen-containing bases
What is the role of helicase in DNA replication?
Unwinds the DNA double helix
What is the directionality of DNA?
3' end and 5' end
How is the leading strand synthesized during DNA replication?
Continuously
What stabilizes the secondary structure of DNA?
Complementary base pairing
Which enzyme is responsible for catalyzing DNA synthesis?
DNA polymerase
What did Meselson and Stahl's experiment support as the mechanism for genetic material duplication?
Semiconservative DNA replication
Which direction does the leading strand synthesize in?
5' -> 3'
What are the regions at the ends of linear chromosomes called?
Telomeres
Which proteins are involved in opening and stabilizing the DNA helix during replication?
Helicase and topoisomerase
What is the name of the short, discontinuous fragments formed on the lagging strand during DNA replication?
Okazaki fragments
In which direction does DNA polymerase work?
5' -> 3'
What is the name of the large multi-enzyme machine responsible for DNA synthesis around the replication fork?
Replisome
What is the name of the mechanism proposed by Watson and Crick for DNA synthesis?
Semiconservative replication
What is the name of the enzyme responsible for joining the Okazaki fragments on the lagging strand?
DNA ligase
Which enzyme is responsible for linking together the Okazaki fragments on the lagging strand during DNA replication?
DNA ligase
What is the consequence of defects in repair enzymes involved in DNA synthesis?
Increased mutation rate
Which enzyme catalyzes the addition of more repeating bases to the end of the lagging strand of telomeres?
Telomerase
What stabilizes the secondary structure of DNA?
Complementary base pairing
In which direction does DNA synthesis occur?
5' -> 3'
What is the primary structure of DNA composed of?
Sugar and phosphate groups
What is the average error rate of DNA replication?
1 error per billion base pairs
What is the role of helicase in DNA replication?
Unwinds the DNA double helix
Which bases form complementary pairs in DNA?
Adenine (A) with Thymine (T)
What is the directionality of DNA?
3' end has an exposed phosphate group
Which hypothesis for DNA replication did the Meselson-Stahl experiment support?
Semiconservative
What is the name of the enzyme responsible for catalyzing DNA synthesis?
DNA polymerase
What is the function of DNA ligase in DNA replication?
Joining Okazaki fragments on the lagging strand
What are the regions at the ends of linear chromosomes called?
Telomeres
In which direction does DNA polymerase work?
5' -> 3'
What stabilizes the DNA helix during replication?
SSBPs
What is the name of the large multi-enzyme machine responsible for DNA synthesis around the replication fork?
Replisome
What occurs during mismatch repair in DNA replication?
Correction of base-pairing errors
What is the consequence of defects in DNA repair genes?
Increased mutation rate
What is the average error rate of DNA replication?
1 in 10^9 base pairs
What is the role of telomerase in DNA replication?
It catalyzes the synthesis of DNA from an RNA template at the end of the lagging strand
What is the function of the nucleotide excision repair system?
It recognizes and removes damaged sections of single-stranded DNA
What is the consequence of defects in DNA repair genes?
Increased likelihood of cancer development
What is the role of DNA polymerase III in DNA replication?
It synthesizes the lagging strand using an RNA primer
What occurs during mismatch repair in DNA replication?
The defective bases are removed and repaired
What type of damage can UV light cause to DNA?
Formation of thymine dimers, causing a kink in the DNA strand
What is the consequence of lacking telomerase in somatic cells?
Shortening of the chromosomes as the individual ages
What is the mechanism proposed by Watson and Crick for DNA synthesis?
Semi-conservative replication
Which disease is characterized by the inability to repair DNA damaged by ultraviolet radiation?
Xeroderma Pigmentosum (XP)
What is the role of DNA ligase in DNA replication?
It connects the new sequence on the lagging strand
Which enzyme is responsible for adding more repeating bases to the end of the lagging strand of telomeres?
Telomerase
What is the average error rate of DNA replication?
1 mistake per billion bases
What occurs during mismatch repair in DNA replication?
Recognition of the mismatched pair and removal of the mismatched base
What stabilizes the secondary structure of DNA?
Single-stranded DNA-binding proteins
What is the consequence of defects in DNA repair genes?
Elevated mutation rate in cells
What type of damage can UV light cause to DNA?
Formation of thymine dimers
What is the function of DNA ligase in DNA replication?
Connecting the Okazaki fragments on the lagging strand
What is the directionality of DNA synthesis?
5' to 3'
Which bases form complementary pairs in DNA?
Adenine and thymine
What is the name of the large multi-enzyme machine responsible for DNA synthesis around the replication fork?
Replisome
Study Notes
DNA Replication: Key Concepts and Processes
- Watson and Crick proposed that DNA strands serve as templates for DNA synthesis, with bases added according to complementary pairing.
- Biologists proposed three hypotheses for how old and new DNA strands interact during replication: semiconservative, conservative, and dispersive.
- Meselson and Stahl's experiment supported semiconservative DNA replication as the mechanism for genetic material duplication.
- DNA polymerase is the enzyme responsible for catalyzing DNA synthesis and can only work in the 5' -> 3' direction.
- Replication begins at the origin of replication and proceeds bidirectionally, forming a replication bubble and fork.
- Proteins like helicase and topoisomerase are involved in opening and stabilizing the DNA helix during replication.
- The leading strand is synthesized continuously in the 5' -> 3' direction, while the lagging strand is synthesized discontinuously away from the replication fork.
- The lagging strand is formed as short, discontinuous fragments called Okazaki fragments, which are later joined by DNA ligase.
- Enzymes responsible for DNA synthesis around the replication fork are organized into a large multi-enzyme machine called the replisome.
- Telomeres are the regions at the ends of linear chromosomes and present challenges for DNA replication due to the inability to replace RNA primers.
DNA Replication: Mechanisms and Processes
- Watson and Crick proposed the template model for DNA replication, with bases added according to complementary base pairing
- Three alternative hypotheses for DNA replication were proposed: semiconservative, conservative, and dispersive
- The Meselson-Stahl experiment supported semiconservative DNA replication as the mechanism for hereditary material duplication
- DNA polymerase is the enzyme that catalyzes DNA synthesis and can only work in the 5' -> 3' direction
- Replication starts at the origin of replication, leading to the formation of replication bubbles and forks
- Proteins like helicase, SSBPs, and topoisomerase open and stabilize the DNA helix during replication
- The leading strand is synthesized continuously in the 5' -> 3' direction, while the lagging strand is synthesized discontinuously
- The lagging strand is synthesized as short fragments called Okazaki fragments and is also known as the discontinuous strand
- Okazaki fragments are later joined together by DNA ligase to form a continuous DNA strand
- Enzymes responsible for DNA synthesis around the replication fork are organized into a large multi-enzyme machine called the replisome
- Telomeres are the regions at the ends of linear chromosomes and present challenges for DNA replication due to the lack of available primers
- As the replication fork reaches the end of a linear chromosome, the RNA primer from the lagging strand cannot be replaced with DNA
Test your knowledge of DNA replication with this quiz covering key concepts and processes. Explore the mechanisms of semiconservative replication, the roles of enzymes like DNA polymerase and helicase, and the challenges posed by telomeres.
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