KEY CONCEPT DNA structure is the same in all organisms

KEY CONCEPT DNA structure is the same in all organisms.

• If you unraveled all your chromosomes from all of your cells and laid out the DNA end to end, the strands would stretch from the Earth to the Moon about 6,000 times.

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Let’s Review!

• What is a macromolecule?

• What are the four kinds of organic molecules?

• What are nucleic acids made of?

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- A large organic molecule (made of carbon!)

- Carbohydrates, lipids, proteins and nucleic acids

- NUCLEOTIDES = Phosphate group, 5-carbon sugar, nitrogenous base

• Nucleic Acids are the chemical link between generations dating back to the beginning of life on earth.

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• A nucleic acid is a complex macromolecule that stores information in cells in the form of a code.

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DNADNA

What are genes made of?Where are genes located?

How do they determine characteristics?

http://upload.wikimedia.org/wikipedia/commons/9/9e/Parallel_telomere_quadruple.png

Try to figure out what happened?

Harmless Disease-causing Heat-killed Harmless & Heat-

bacteria bacteria disease causingkilled disease causing

Disease-causing bacteria (smooth

colonies)

Harmless bacteria (rough colonies)

Heat-killed, disease-causing bacteria (smooth colonies)

Control(no growth)



Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)

Dies of pneumonia

Section 12-1

Figure 12–2 Griffith’s Experiment

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Disease-causing bacteria (smooth

colonies)



Control(no growth)



Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)

Dies of pneumonia

Section 12-1

Figure 12–2 Griffith’s Experiment

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Some History• While Frederick Griffith was

experimenting with pneumonia, he discovered that mice injected with dead bacteria still died of pneumonia… so it was something inside the bacteria that was still passed on to the next generation.

• Oswald Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next.

Some More History

• Alfred Hershey and Martha Chase concluded that the genetic material of the bacteriophage (a virus that “eats” bacteria) is DNA, not protein.

Bacteriophage with phosphorus-32 in DNA

Phage infectsbacterium

Radioactivity inside bacterium

Bacteriophage with sulfur-35 in protein coat


No radioactivity inside bacterium

Figure 12–4 Hershey-Chase ExperimentSection 12-1

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DNA

• Genes are made of DNA = deoxyribonucleic acid

• How could DNA code for everything genes do?– Genes had to carry information from one

generation to the next– Genes had to put that information to work

by determining the inheritable characteristics of organisms

– Genes had to be easily copied, because it is replicated every time the cell divides

DNA StructureDNA Structure

• Double Helix • (twisting ladder) • modeled by

Watson & Crick 1953

• Sides/backbone - alternating deoxyribose sugar & phosphate

• “Rungs” - nitrogen bases held together by hydrogen bonds

The Double Helix• Rosaline Franklin’s x-ray

showed that two DNA strands are twisted around each other.

• James Watson and Francis Crick used Franklin’s x-ray to make a model of DNA.

• Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other.

• Watson and Crick also discovered that hydrogen bonding held the nitrogenous bases together.

http://upload.wikimedia.org/wikipedia/commons/9/9e/Parallel_telomere_quadruple.png

DNADNA• DNA = DeoxyriboNucleic AcidDNA = DeoxyriboNucleic Acid

– Short nucleic acid Short nucleic acid

– A polymer that stores genetic A polymer that stores genetic informationinformation

– Found in the chromosomes of all Found in the chromosomes of all organismsorganisms

– Controls production of proteins Controls production of proteins depending on sequence of depending on sequence of nitrogen basesnitrogen bases

– Unit of structure = nucleotideUnit of structure = nucleotide

DNADNA• Nucleotide – 3 partsNucleotide – 3 parts

1.1. A phosphate group – POA phosphate group – PO44

2.2. A 5 carbon sugar – deoxyriboseA 5 carbon sugar – deoxyribose

3.3. A nitrogen baseA nitrogen base

Draw the Picture

Base PairingBase PairingBase Pairing According to Base Pairing According to Chargaff’s Chargaff’s

RuleRule

• The complementary bases always pair a certain purine with a certain pyrimidine

Base Base

A = A = adenineadenine

T = T = thyminethymine

C = C = cytosinecytosine

G = G = guanineguanine

Complementary Complementary BaseBase

thyminethymine

adenineadenine

guanineguanine

cytosinecytosine

Base Pairing Rule:Base Pairing Rule:

– AA always pairs with always pairs with TT

– CC always pairs with always pairs with GG

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Nitrogen BasesNitrogen Bases• Nitrogen Bases – name source Nitrogen Bases – name source

for the nucleotidesfor the nucleotides

• 2 different types:2 different types:

– Purines – double ringPurines – double ring• AdenineAdenine • GuanineGuanine

– Pyrimidines – single ringPyrimidines – single ring• CytosineCytosine• ThymineThymine

Nitrogen BasesNitrogen Bases

Purines Pyrimidines

Adenine Guanine Cytosine Thymine

Phosphate groupDeoxyribose

DNA Structure

Phosphate

Group Deoxyribose Sugar

Nitrogenous Base

Weak Hydrogen Bonds

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Figure 12–7 Structure of DNASection 12-1

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Let’s pair up DNA!• What would pair up with ATCG?

TAGC• What would pair up with

ATTAGC?

TAATCG• What would pair up with

ATACGGTC?

TATGCCAG

Replication – General InfoReplication – General Info

• The exact copying of DNAThe exact copying of DNA

• DNA must be copied before DNA must be copied before cells divide cells divide each daughter each daughter cell has a complete set of cell has a complete set of DNADNA

• Original strands serve as Original strands serve as templates for new strandstemplates for new strands

• Replication occurs in both Replication occurs in both directionsdirections

Replication – General InfoReplication – General Info

How it happens:

1.Helicase (enzyme) unwinds the DNA by breaking hydrogen bonds

2. DNA polymerase (enzyme) joins individual nucleotides to each separated strand, producing DNA molecule

**DNA polymerase also proofreads each new DNA strand to make perfect copies

Results of Replication

2 DNA molecules 2 DNA molecules each contains one each contains one original original

strand & one new strand (semi-strand & one new strand (semi-conservative)conservative)

Review of The Genetic Code

• The sequence of nitrogen bases (A,T,C & G) along a DNA strand code for the synthesis (making) of specific proteins.

• According to Chargaff’s Rule:– A bonds with T– C bonds with G

What are chromosomes???

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Nucleotides make up DNA DNA winds into ChromatinChromatin condenses into

ChromosomesChromosomes contain GenesGenes are sections of DNATHAT CODE FOR PROTEINS

Chromosomes contain Instructions for making YOU!!!

• Proteins are made in the ribosomes outsideoutside the nucleus.

• DNA is copied (replicated) in the nucleus but cannot leave the nucleus.

THEREFORE…….

• A message must be sent to the ribosomes in the cytoplasm telling them what proteins to make.

• This message is carried by a nucleic acid called messenger (mRNA ).

RNA Structure

1. RNA is a single strand2. RNA has the sugar ribose3. Adenine bonds with Uracil (NOT thymine).4. Can leave the nucleus

RNA differs from DNA in 4 ways:

Differences Between

• DNA• Deoxyribose

Sugar• Double Stranded• A, C, T, G• Remains in

nucleus

• RNA• Ribose sugar• Single Stranded• A, C, U, G• Moves out of

nucleus

2. Which scientists came up with the double helix model of DNA?

1. How many strands does DNA have?

a. Hershey & Chasec. Galileo & Aristotle

b. Watson and Crickd. Darwin & Malthus

a. one b. twoc. three d. four

Let’s wrap it up with a few questions together…

3. What holds the strands of DNA together?

5. What DNA bases would pair up with GAATCC?

c. CGGAGG

a. CTTAGG

d. GCCTCC

b. GAATCC

a. Phosphate Group

b. Deoxyribose Sugarc. Hydrogen Bonds d. Nitrogen bonds

4. What DNA bases would pair up with CATTAT? a. CATTAT b. TATTAC

c. GTAATA d. GUAAUA

Is your answer the same as earlier…•What are genes made of?

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KEY CONCEPT DNA structure is the same in all organisms