dna and rna – dna image

DNA and RNA

• What do all of these organisms have in common?

They all share a universal genetic code.

How do we know that all of our genetic information comes from DNA?

Thanks to many scientists and many experiments over the last ≈ 90 years.

Let’s take a look…….

Who helped?• In 1928: Griffith accidentally

discovered a process called Transformation that turned non-deadly bacteria into deadly pneumonia causing bacteria.

• In 1944: Avery, McCarty, and MacLeodRepeated Griffith’s Experiment

• Discovered DNA was the transformation factor.

• In 1952: Hershey-Chase experimented with bacteria and bacteriophages. Showed DNA was what entered the bacteria and caused disease.

Now we know!

DNA carries the genetic code!

But, how do we know how it works?

How did DNA:

DNA’s Structure was the key!

2. Duplicate itself easily?

1. Store information?

The Race to Discover DNA’s Structure

1950Chargaff’s Rule: Equal amounts of Adenine and Thymine, and equal amounts of Guanine and Cytosine

Erwin Chargaff

Why do you think the bases match up

this way?

Purine + Purine = Too wide

Pyrimidine + Pyrimidine = Too Narrow

Purine + Pyrimidine = Perfect Fit from X-ray data


Maurice Wilkins

Rosalind Franklin

X-Ray diffraction image of DNA taken by Franklin in

1951


James Watson Francis Crick

1953Compiled data from previous scientists to build a double-helical model of DNA

DNA and RNA are Nucleic Acids• What is a nucleic acid?

• Nucleic acids are one of the major organic biomolecules.

Nucleic Acids• They contain C, H,

N, O, P• They are made of

nucleotide monomers

• They store information• The instructions makes

proteins

• Examples: DNA & RNA

sugar

phosphate

nitrogen base

DNA Structure• What does DNA stand for?• What is the monomer for nucleic acids?• What is the structure of this monomer?

nucleotide

N base

PO4

SugarSugar

PO4

N baseThe numbers are the positions of the carbons on the sugar.

(the 3’ end)

5

4

3 2

1

(the 5’ end)

DeoxyriboNucleic Acid

A DNA NUCLEOTIDE

H

H2

H H

H3

HH H

H

H

O

O

O

C C

C

N

N

PO

O

O

C

C

C C

C

O

OO

C

C

1.

2.

3.

1.

2.

3.1. Phosphate Group2. 5-Carbon Sugar (Dexoyribose)3. Nitrogen Base

1. Phosphate Group

2. 5-Carbon Sugar(Dexoyribose)

3. Nitrogen Base

DNA Nucleotides• There are four nitrogen bases making up four

different nucleotides.

Adenine

Guanine

Thymine

CytosinePyrimidines

PurinesA

C

G

T

N base

Chargaff’s Base Pair Rules• Adenine always bonds with thymine.

• Guanine always bonds with Cytosine.

The lines between the bases represent hydrogen bonds

A

CG

T

C

G

A

A

T

G

Nucleotide PS

N-b

Pairing DNA Nucleotides• What is a nucleotide?

Rule

A to T

C to G

What is the base pairing rule?What would be the complementary nucleotide pairing?

3’End

3’End 5’End

5’End

DNA

DOUB

LE H

ELIX

ladder shaped molecule

Purpose of DNA• DNA contains our genetic code which codes

for proteins.• It is our “blueprint”…all cells have the same

blueprint, but only certain parts are looked at when building different cells

What is RNA?• RNA stands for

RiboNucleic Acid• DNA must have a “helper”

molecule. (DNA is too fat)

• RNA is a single stranded nucleic acid

• made up of monomers called nucleotides

sugar

phosphate

nitrogen base

A

B

C

RNA Nucleotides• A - Sugar (ribose)• B - Phosphate• C - Nitrogen base

sugar

phosphate

nitrogen base

Phosphate Group

Nitrogen Base

Sugar

(ribose)

RNA• Identify the parts of the RNA strand.

• Adenine bonds with Uracil.

• Guanine bonds with Cytosine.

A

CG

U

Rules for Base Pairing

DNA makes RNA• C = G

• A = U

3’ DNA strand

5’ DNA strandRNA strand

C

A

T

G

G

U

C

A

What is the function of RNA?• Carries the coded “message” of DNA.• Translates the “message” into proteins

• 3 Types of RNA• Messenger RNA (mRNA)• Transfer RNA (tRNA)• Ribosomal RNA (rRNA)

DNA RNASugar is deoxyribose

Sugar is ribose

Adenine base is present

Cytosine base is present

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Comparing DNA & RNA

DNA RNAGuanine base is present

Thymine base is present

Uracil base is present

Shape is double helix

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Comparing DNA & RNA

DNA RNAShape is single stranded

Located in nucleus

Located in cytoplasm

Stores genetic information

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√

Comparing DNA & RNA

DNA RNAFunctions in protein synthesis

Composed of nucleotides

Instructions (template) for synthesis of proteinsTranscribes and Translates the templateMore than one type

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Comparing DNA & RNA

dna and rna – dna image

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