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www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information.

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Page 1: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

www.BioEdOnline.org

Essential Idea

The structure of DNA allows efficient storage of genetic information.

Page 2: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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Understandings

The nucleic acids DNA and RNA are polymers of nucleotides.

DNA differs from RNA in the number of strands present, the base composition and the type of pentose.

DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.

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Discovery of DNA movie

The animation below describes the discovery of the DNA molecule.

http://media.hhmi.org/biointeractive/films/Double_Helix.html

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IB ASSESSMENT STATEMENT

Outline (summarize) DNA nucleotide structure. Include the following terms:

sugar (deoxyribose), base phosphate. Be sure to describe the relative positions of

the above terms.

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Nucleic Acids

Nucleic Acids are information molecules of cells.

They contain the genetic code for all living organisms.

There are two type of nucleic acids:

1. DNA – Deoxyribonucleic acid

2. RNA – Ribonucleic acid

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Nucleic Acids

Nucleic Acids are polymers made of monomers call nucleotides

Nucleotides consist of three substances:

1. Nitrogenous Bases

2. Pentose Sugar

3. Phosphoric Acid

The Animation below shows explains the structure of DNA.

http://www.sumanasinc.com/webcontent/animations/content/DNA_structure.html

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The Molecular Components of DNA and RNA (II)

The Sugar – Phosphate Backbone DNA – Deoxyribose (Pentose) Sugar RNA – Ribose (Pentose) Sugar Phosphate Group

Base + Sugar + Phosphate = Nucleotide

Deoxyribose + Triphosphate Group Ribose + Triphosphate Group

BASE BASE

1’

2’3’

5’1’

2’3’

5’

2005 VisiScience Corporation All Rights Reserved

Page 9: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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The Molecular Components of DNA and RNA (I)

Bases DNA and RNA

Adenine (A) Cytosine (C) Guanine (G)

DNA Only Thymine (T)

RNA Only Uracil (U)

2005 VisiScience Corporation. All Rights Reserved.

Uracil

ThymineGuanine

Adenine Cytosine

Page 10: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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The DNA and RNA Strand

Nucleotide + Nucleotide(n)

= DNA (or RNA) strand

Deoxyribonucleotides = DNA

Ribonucleotides = RNA

2005 VisiScience Corporation. All Rights Reserved.

3'

5'

Base

Base

Base

1'

3'

5'

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RNA vs. DNA

DNA is Double Stranded – Double Helix

RNA is Single Stranded

Page 12: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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IB ASSESSMENT STATEMENT

Identify the names of the four nitrogenous bases in DNA.

Page 13: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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5'

5'

3'

3'

DNA is Double-Stranded

Hydrogen bonds enable the DNA ladder.

A always pairs with T. C always pairs with G.

The sequence of one strand predicts the sequence of the other.

2005 VisiScience Corporation. All Rights Reserved.

3

45

21

4

5

1

6

32

87

96

Thymidine

Two Hydrogen Bonds

Adenosine

93

45

2

4

5

1

6

32

7

6

1

8Cytidine

Guanosine

Three Hydrogen Bonds

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RNA vs. DNA

Page 15: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

KEY CONCEPT DNA structure is the same in all organisms.

DNA Animation: https://www.youtube.com/watch?v=8kK2zwjRV0M

Page 16: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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IB ASSESSMENT STATEMENT

Outline (summarize) how DNA nucleotides are linked (bonded) together by covalent bonds into a single strand.

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DNA is composed of two polynucleotides chains.

Nucleotides are covalently bonded between the phosphate of one nucleotide to the C3 of the second nucleotide.

The phosphate group creates a bridge connecting C5 on one pentose with the C3 on the next pentose.

The bond is a phosphodiester bond which indicates that there are two covalent bonds formed between the -OH and the acidic phosphate group

Page 21: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

The sugar phosphate backbone which provides the stable backbone of one of the helices.

Covalent bonds that link the nucleotides along the backbone of the molecule.

The bases projecting into the centre.

.

Page 22: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

At one end there is pentose with 5' (said "five prime" ) carbon which is free from bonding.

At the other end there is a 3' carbon free from bonding to other nucleotides.

Additional nucleotides are joined to the 3' end of the existing polynucleotide chain.

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IB ASSESSMENT STATEMENT

Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds.

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Chargaff’s rule Animation

http://www.hhmi.org/biointeractive/chargaffs-ratio

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TAC

G

Nucleotides always pair in the same way. The base-pairing rules show

how nucleotides always pair up in DNA.

Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width.

– A pairs with T– C pairs with G

Page 27: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width.

Cytosine always pairs with guanine

Thymine always pairs with Adenine.

Page 28: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

hydrogen bond covalent bond

The bases are connected by hydrogen bonds.

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IB Assessment State

Draw and label a simple diagram of the molecular structure of DNA. Be sure to show the following

the complementary base pairs of A–T and G–C, held together by hydrogen bonds

and the sugar–phosphate backbones.

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Two polynucleotide chains.

Two anti-parallel chains.

a)The number followed by the prime (') determined the carbon in deoxyribose free from bonding to another nucleotide.

b) Note that the two chains are in opposite directions 3' to 5' is parallel to 5' to 3' chain.

The anti-parallel chains have a uniform distance (2nm) between the outside of the two sugar phosphate backbones

Complementary base pairs: Inside the double helix bases form one strand hydrogen bond to bases on the opposite strand but always in the following way:

a) Adenine hydrogen binds to Thymine b) Cytosine hydrogen bonds to Guanine

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IB Assessment Statement

Draw & Label a Simple diagram of the molecular structure of DNA

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DNA and Chromosomes Eukaryotic Chromosome Structure

Chromosome

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Nature of Science

Using models as representation of the real world—Crick and Watson used model making to discover the structure of DNA. (1.10)

Page 35: Www.BioEdOnline.org Essential Idea The structure of DNA allows efficient storage of genetic information

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Application & Skill

Application: Crick and Watson’s elucidation of the structure of DNA using model making.

Skill: Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.