Questions and Answers
What is the process of copying double-stranded DNA to produce an identical double-stranded DNA called?
What enzyme separates the DNA strand into two separate strands?
Helicase
What are the single strand binding proteins that prevent reannealing of single-stranded DNA?
SSB Protein
Which enzyme creates RNA primers needed to start the replication process?
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Which component helps hold polymerase on the DNA strand during replication?
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What removes RNA primers that previously began the synthesis?
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What enzyme links short DNA chains to create one long continuous DNA strand?
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What are the DNA pieces that are separated due to the lagging strand called?
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What model represents the mechanism by which DNA is replicated in cells, consisting of half parental DNA and half new DNA?
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What is the continuously synthesized strand during DNA replication called?
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What is the discontinuously synthesized strand during DNA replication called?
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In what direction do DNA strands replicate?
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Study Notes
DNA Replication Overview
- DNA replication involves duplicating a double-stranded DNA molecule to produce two identical strands, essential for heredity.
Key Enzymes and Proteins
- Helicase: An enzyme that unwinds and separates DNA strands, forming two single strands during replication.
- SSB Protein: Coats single-stranded DNA to prevent reannealing, ensuring the strands remain separated for replication; consists of 178 amino acids.
- Primase: Creates RNA primers necessary to initiate the synthesis process; classified as a type of RNA polymerase.
- Sliding Clamp: Assists in holding DNA polymerase onto the DNA strand, enhancing the process of replication.
- RNase H: Responsible for removing RNA primers used during the initial steps of DNA synthesis.
- DNA Ligase: Joins short DNA fragments into a continuous DNA strand, mainly functioning on the backbone of the DNA.
Structure and Function of DNA Strands
- Okazaki Fragments: Short DNA segments formed on the lagging strand due to the discontinuous nature of its synthesis; identified by scientist Reiji Okazaki.
- Semi-conservative Model: Each daughter DNA strand contains one original (parental) and one new strand, promoting genetic continuity.
Leading and Lagging Strands
- Leading Strand: Synthesized continuously, allows for straightforward addition of nucleotides during replication.
- Lagging Strand: Synthesized discontinuously, leading to the creation of fragments that must be later joined together.
Directionality of DNA Synthesis
- DNA replication occurs from the 5' to 3' direction; DNA polymerase attaches nucleotides in this specific orientation. Okazaki fragments form as a result of DNA polymerase working in the 3' to 5' direction.
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