DNA:DNA: DNA:DNA:

An Introduction to structure and functionAn Introduction to structure and function

Hopefully a reviewHopefully a review

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Questions to be able to answer:Questions to be able to answer:Questions to be able to answer:Questions to be able to answer:

What are the functions and types of DNA?What are the functions and types of DNA? What are chromosomes and how many do we What are chromosomes and how many do we

have?have? Draw a labeled sketch of DNADraw a labeled sketch of DNA Draw the nucleotide structureDraw the nucleotide structure Pyramidines or purines?Pyramidines or purines? Why is DNA like a zipper?Why is DNA like a zipper? How are bases held together?How are bases held together? How do bases pair?How do bases pair? Sketch DNA replicationSketch DNA replication How does DNA hold information?How does DNA hold information?

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The Human Genome Project — DNA VideoThe Human Genome Project — DNA VideoThe Human Genome Project — DNA VideoThe Human Genome Project — DNA Video

• http://www.nclack.k12.or.us/18242019171932910/blank/browse.asp?A=383&BMDRN=2000&BCOB=0&C=64959

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The Importance of DNAThe Importance of DNAThe Importance of DNAThe Importance of DNA

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DNA by the numbersDNA by the numbersDNA by the numbersDNA by the numbers• A human has 46

chromosomes, a plum tree has 48, a chicken has 78 and an ant has 2

• Each human cell has about 2m of DNA

• The average human has 75 trillion cells

• The 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

The earth is 150 billion mThe earth is 150 billion mor 93 million miles from or 93 million miles from the sun.the sun.

The earth is 150 billion mThe earth is 150 billion mor 93 million miles from or 93 million miles from the sun.the sun.

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DNADNADNADNA• DNA is often called the

blueprint of life - Why?

• In simple terms, DNA contains the instructions for making proteins within the cell.

• DNA stands for DDeoxyriboeoxyribonnucleic ucleic aacidcid. .

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Functions of DNAFunctions of DNA• Two primary functionsTwo primary functions

- - transmit information from one transmit information from one generation to the nextgeneration to the next

- provide blueprint for making proteins - provide blueprint for making proteins the same way every timethe same way every time

Two Types of DNATwo Types of DNA

• nuclear or chromosomal DNA (inherited from nuclear or chromosomal DNA (inherited from mother and father)mother and father)

• mitochondrial DNA (inherited from mother mitochondrial DNA (inherited from mother only)only)

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Why do we study DNA?Why do we study DNA?Why do we study DNA?Why do we study DNA?• Importance to all life on Earth• Medical benefits such as cures

for diseases• Genetic Engineering

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Chromosomes and DNAChromosomes and DNAChromosomes and DNAChromosomes and DNA

• Chromosomes are made up of a chemical called DNA

• Genes are coded for in different regions of chromosomes

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ChromosomesChromosomes

• Our body’s way of organizing all the information that our genetic material contains

• 23 pairs in humans

- Each pair contains one from mother and one from father

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The Shape of the MoleculeThe Shape of the MoleculeThe Shape of the MoleculeThe Shape of the Molecule

DNA is a very long polymer

The basic shape is like a twisted ladder

double helix

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The Double Helix MoleculeThe Double Helix MoleculeThe Double Helix MoleculeThe Double Helix Molecule

• The DNA double helix has two strands twisted together — looks like a twisted ladder.

• Need to look at the structure of one strand

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Finding the StructureFinding the StructureFinding the StructureFinding the Structure

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One Strand of DNAOne Strand of DNAOne Strand of DNAOne Strand of DNA

deoxyribosedeoxyribosedeoxyribosedeoxyribose

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One Strand of DNAOne Strand of DNAOne Strand of DNAOne Strand of DNA

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NucleotidesNucleotidesNucleotidesNucleotides

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

nucleotidenucleotide..

C C

C

OPhosphate

O

CC

O -P OO

O Nitrogenous base

Deoxyribose

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The Structure of DNAThe Structure of DNAThe Structure of DNAThe Structure of DNA

• One strand of DNA is a polymer of nucleotides• One strand of DNA has many millions of nucleotides

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Four nitrogenous basesFour nitrogenous basesFour nitrogenous basesFour nitrogenous bases

DNA has four different bases

•Cytosine C• Thymine T

• Adenine A

• Guanine G :

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Four Nitrogenous BasesFour Nitrogenous BasesFour Nitrogenous BasesFour Nitrogenous Bases

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Easy to Remember Shapes for DiagramsEasy to Remember Shapes for DiagramsEasy to Remember Shapes for DiagramsEasy to Remember Shapes for Diagrams

Cytosine C

Thymine T

Adenine A

Guanine G

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Curved Lines go TogetherCurved Lines go Together

Curved Lines go TogetherCurved Lines go Together

Straight Lines go TogetherStraight Lines go Together

Straight Lines go TogetherStraight Lines go Together

Two Kinds of Bases in DNATwo Kinds of Bases in DNATwo Kinds of Bases in DNATwo Kinds of Bases in DNA

• Pyrimidines are single ring bases

• Purines are double ring bases

C

C

C

C

N

N

OO

N

CC

CC

N

N

N

N

N

C

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Pyrimidines: Pyrimidines: Thymine and CytosineThymine and CytosinePyrimidines: Pyrimidines: Thymine and CytosineThymine and Cytosine

• Thymine and cytosine each have one ring of carbon and nitrogen atoms

C

C

C

C

N

N

OO

N

CytosineCytosine

C

C

C

C

N

N

OO

OO

ThymineThymine

C

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Purines: Purines: Adenine and GuanineAdenine and GuaninePurines: Purines: Adenine and GuanineAdenine and Guanine

• Adenine and guanine each have two rings of carbon and nitrogen atoms

C

C

C

C

N

N

N

AdenineAdenine N

N

C

C

C

C

C

N

N

OO

N

GuanineGuanineN

N

C

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Two Stranded DNATwo Stranded DNATwo Stranded DNATwo Stranded DNA

• DNA has two strands that fit together something like a zipper• The teeth are the nitrogenous bases but why do they stick

together?

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Hydrogen BondsHydrogen BondsHydrogen BondsHydrogen Bonds• The bases attract

each other because of hydrogen bonds

• Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA

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Hydrogen Bonds, cont.Hydrogen Bonds, cont.Hydrogen Bonds, cont.Hydrogen Bonds, cont.

• When making hydrogen bonds, cytosine always pairs up with guanine — C-G or G-C

• And adenine always pairs up with thymine — A-T or T-A

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Important:Important:Important:Important:• Adenine and Thymine always Adenine and Thymine always

join togetherjoin togetherA TA T

• Cytosine and Guanine always Cytosine and Guanine always join togetherjoin together

C GC G

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DNA ReplicationDNA Replication

• DNA is unwoundDNA is unwound

• An enzyme An enzyme called DNA called DNA Polymerase adds Polymerase adds complementary complementary bases to “single bases to “single stranded”stranded”

- A with T- A with T

- C with G- C with G

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DNA ReplicationDNA ReplicationDNA ReplicationDNA Replication

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TranscriptionTranscriptionTranscriptionTranscription

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PracticePracticePracticePractice

• Simple replication

Draw the replication for the sequence of Draw the replication for the sequence of bases:bases:

Include labels of the backbone Include labels of the backbone structure and the hydrogen bondsstructure and the hydrogen bonds

Include labels of the backbone Include labels of the backbone structure and the hydrogen bondsstructure and the hydrogen bonds

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The Structure of DNA:The Structure of DNA:The Structure of DNA:The Structure of DNA:

Can you do these things?• Make a labeled sketch

• Label the structure of a nucleotide

• Know which bases pair up and how they are held together

• Explain why the structure of the DNA Molecule is often described as a zipper.

• Make a sketch of DNA replication

• Explain how DNA holds information

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