IB Biology Topic 7.1 DNA Structure and Replication Notes & Questions (SL/HL)

IB Biology Topic 7.1 DNA Structure and Replication Notes & Questions (SL/HL) | RevisionDojo

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7.1 DNA Structure and Replication

Introduction

In this section, we will explore the intricate structure of DNA and the mechanisms by which it replicates. This knowledge is fundamental to understanding genetics, molecular biology, and the continuity of life.

7.1.1 DNA Structure

Components of DNA

Nucleotides: The building blocks of DNA, consisting of a phosphate group, a deoxyribose sugar, and a nitrogenous base. The four nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G).
Double Helix: DNA is structured as a double helix, with two strands running in opposite directions (antiparallel). The strands are held together by hydrogen bonds between the nitrogenous bases (A pairs with T, and C pairs with G).

Nucleosomes

Histones: Eukaryotic DNA is wrapped around histone proteins to form nucleosomes. Each nucleosome consists of DNA wrapped around an octamer of histones.
Supercoiling: Nucleosomes further coil to form a compact structure, aiding in the efficient packaging of DNA within the nucleus.

Example

Imagine twisting an elastic band repeatedly; it starts to coil upon itself. This is similar to how DNA supercoils.

DNA Supercoiling

Function: Supercoiling helps in saving space and protecting DNA from damage. It also facilitates the movement of chromosomes during cell division.

7.1.2 Mechanism of DNA Replication

Basic Steps

Initiation: DNA replication begins at specific locations called origins of replication. The enzyme helicase unwinds the double helix, creating a replication fork.
Elongation: DNA polymerase adds nucleotides to the growing DNA strand in a 5’ to 3’ direction. Due to the antiparallel nature of DNA, replication proceeds differently on the two strands:

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Note

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Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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7.1 DNA Structure and Replication

Introduction

7.1.1 DNA Structure

Components of DNA

Nucleotides: The building blocks of DNA, consisting of a phosphate group, a deoxyribose sugar, and a nitrogenous base. The four nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G).
Double Helix: DNA is structured as a double helix, with two strands running in opposite directions (antiparallel). The strands are held together by hydrogen bonds between the nitrogenous bases (A pairs with T, and C pairs with G).

Nucleosomes

Histones: Eukaryotic DNA is wrapped around histone proteins to form nucleosomes. Each nucleosome consists of DNA wrapped around an octamer of histones.
Supercoiling: Nucleosomes further coil to form a compact structure, aiding in the efficient packaging of DNA within the nucleus.

Example

Imagine twisting an elastic band repeatedly; it starts to coil upon itself. This is similar to how DNA supercoils.

DNA Supercoiling

Function: Supercoiling helps in saving space and protecting DNA from damage. It also facilitates the movement of chromosomes during cell division.

7.1.2 Mechanism of DNA Replication

Basic Steps

Initiation: DNA replication begins at specific locations called origins of replication. The enzyme helicase unwinds the double helix, creating a replication fork.
Elongation: DNA polymerase adds nucleotides to the growing DNA strand in a 5’ to 3’ direction. Due to the antiparallel nature of DNA, replication proceeds differently on the two strands:

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology 7.1 DNA Structure and Replication Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

7.1 DNA Structure and Replication

Introduction

7.1.1 DNA Structure

Components of DNA

Nucleosomes

DNA Supercoiling

7.1.2 Mechanism of DNA Replication

Basic Steps

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

7.1 DNA Structure and Replication

Introduction

7.1.1 DNA Structure

Components of DNA

Nucleosomes

DNA Supercoiling

7.1.2 Mechanism of DNA Replication

Basic Steps

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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