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Questions and Answers
Why does DNA need to replicate before cells divide?
Why does DNA need to replicate before cells divide?
DNA replicates before a cell divides to give a complete set of genetic instructions to each daughter cell.
What is Deoxyribose?
What is Deoxyribose?
A sugar derived from ribose by replacing a hydroxyl group with hydrogen.
What is a Nitrogenous base?
What is a Nitrogenous base?
An organic molecule that has a nitrogen atom, along with chemical properties of a base. The function of this base is to bond nucleic acids together.
What holds the base pairs in place?
What holds the base pairs in place?
What is the function of Helicase?
What is the function of Helicase?
What role does DNA polymerase play?
What role does DNA polymerase play?
What is Primase?
What is Primase?
What is the function of Ligase?
What is the function of Ligase?
In what direction does polymerase build?
In what direction does polymerase build?
In what direction does polymerase read?
In what direction does polymerase read?
What is the leading strand?
What is the leading strand?
What is the lagging strand?
What is the lagging strand?
What holds complementary bases (A & T) together?
What holds complementary bases (A & T) together?
What is the first step in DNA replication?
What is the first step in DNA replication?
The two separated strands will act as ____________________ for making the ___________________________________.
The two separated strands will act as ____________________ for making the ___________________________________.
Why is DNA replication said to be semi-conservative?
Why is DNA replication said to be semi-conservative?
What enzyme unwinds the DNA strands?
What enzyme unwinds the DNA strands?
DNA pieces separated by primers in the lagging strand are called?
DNA pieces separated by primers in the lagging strand are called?
List the 4 events that must occur in the lagging strand prior to completing its replication.
List the 4 events that must occur in the lagging strand prior to completing its replication.
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Study Notes
DNA Replication Overview
- DNA replication is essential before cell division to ensure each daughter cell receives a full set of genetic instructions.
- The process is semi-conservative, resulting in each new helix containing one original strand and one newly synthesized strand.
Key Components
- Deoxyribose: A sugar formed by replacing a hydroxyl group in ribose with a hydrogen atom.
- Nitrogenous Base: Organic molecules with nitrogen that bond nucleic acids together, crucial for genetic coding.
- Hydrogen Bonds: Bonds that hold the complementary nitrogenous base pairs (A & T) together.
Enzymes Involved
- Helicase: Responsible for unzipping the DNA double helix, separating the two strands.
- DNA Polymerase: Acts as the builder, adding nucleotides to form the new DNA strand.
- Primase: Initiates DNA synthesis by creating RNA primers that indicate where DNA polymerase should start.
- Ligase: Functions as the gluer, sealing gaps between DNA fragments to create a continuous strand.
Strand Characteristics
- Leading Strand: Synthesized continuously in the 5'-3' direction; DNA polymerase reads the template in the 3'-5' direction.
- Lagging Strand: Synthesized in segments called Okazaki fragments; built in the opposite direction (5'-3'), requiring the polymerase to work backwards, filling gaps as helicase unzips.
DNA Replication Process
- The first step of DNA replication is to unzip the double helix.
- The separated strands of DNA serve as templates for synthesizing new strands.
- Lagging strand replication involves multiple steps: helicase unwinds the DNA, SSB proteins stabilize strands, primase synthesizes RNA primers, and DNA polymerase extends the strand from the primer.
Summary of Important Terms
- Templates: The separated DNA strands that guide the synthesis of new DNA strands.
- Okazaki Fragments: Short segments of DNA synthesized on the lagging strand.
- SSB Proteins: Single-stranded binding proteins that help keep the DNA strands apart during replication.
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