Deoxyribonucleic Acid

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Deoxyribonucleic Acid
The Structure of DNA
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DNA is

1. Blueprint of life
2. Instructions for making proteins
3. Found in our chromosomes
4. All of these

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Why do we study DNA?

1. Very important to life
2. For the medical benefits
3. Better food crops
4. All of these

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DNA

• Called the blueprint of life
• Contains the instructions for making proteins
• Discovered by Watson and Crick in 1953
• NoteRosalind Franklin
• Made the discovery, she died.

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Why do we study DNA?

• Central importance to all life on Earth
• Medical benefits such as cures for diseases
• Better food crops.

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Chromosomes and DNA

• Genes are on our chromosomes
• Chromosomes are DNA

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The Shape of the Molecule

• DNA is a very long polymer.
• Shaped like a twisted ladder or zipper.
• Called a double helix

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One Strand of DNA
phosphate

• Backbone is alternating phosphates and
  deoxyriboses
• Rungs are nitrogenous bases

deoxyribose
bases
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One Strand of DNA
nucleotide

• Polymer of nucleotides.
• Sequence of nucleotide bases determines type of
  protein
• Many millions of nucleotides.

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Nucleotides

• One deoxyribose together with its phosphate and
  base make a nucleotide

Nitrogenous base
O
Phosphate
C
C
C
Deoxyribose
O
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What is located on our chromosomes?

• Jeans
• Ribosomes
• Genes
• Proteins

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Who discovered DNA?

1. Robert Hooke
2. Watson and Crick
3. Crick and Hooke
4. Watson and Hooke

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The shape of the DNA molecule is called

1. Double ladder
2. Double helix
3. Double string
4. None of these

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The backbone of the DNA is alternating

1. Phosphate and base
2. Phosphate and ATP
3. Phosphate and deoxyribose
4. Deoxyribose and base

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What is the subunit of DNA?

1. Nucleus
2. Nucleolus
3. Nucleoplasm
4. Nucleotide

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The protein made is determined by

1. Number of nucleotides
2. Sequence of nucleotides
3. Type of nucleotide
4. None of these

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Four nitrogenous bases
DNA has four different bases

• Cytosine C
• Thymine T
• Adenine A
• Guanine G

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Two Kinds of Bases in DNA
N

• Pyrimidines are single ring bases
• Cytosine/thymine
• Purines are double ring bases
• Adenine/guanine

C
N
C
C
O
C
N
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Hydrogen Bonds

• Bases held together by hydrogen bonds
• Cytosine always pairs up with guanine
• CG
• Adenine always pairs up with thymine
• AT

Hydrogen bond
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DNA by the numbers

• Cell has about 2 m of DNA
• Average human has 75 trillion cells
• Average human has enough DNA to go from the earth
  to the sun more than 400 times
• DNA has a diameter of only 0.000000002 m

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Show Video

• http//sciencenetlinks.com/interactives/dna.swf

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What is the correct base pairing?

1. C-T and G-A
2. G-T and C-A
3. A-T and G-C
4. A-C and T-A

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Pyrimidines have.

1. Single ring
2. Double ring
3. Triple ring
4. All of these

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Bases are held together by

1. Peptide bonds
2. Covalent bonds
3. Ionic bonds
4. Hydrogen bonds

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Replication

• Before a cell divides
• Makes two exact copies

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Process

• DNA unwinds
• Enzyme DNA Helicase unzips the DNA molecule
• Unpaired nucleotides bond with free floating
  nucleotides with the aid of DNA polymerase
• Process goes in both directions
• One old original strand and one new strand

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Process of making an exact copy of DNA is

• Transcription
• Translation
• Replication

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What is the name of the enzyme that unzips DNA?

1. RNA polymerase
2. RNA Helicase
3. DNA Helicase
4. DNA polymerase