DNA-The code of life Why don’t we all look alike?.

DNA-The code of life

Why don’t we all look alike?

WARM-UP #7

Why do we Study DNA?

1. Disease2. Better vegetable, fruit, and animals.3. Crime4. History of life

DNA Facts

•One chromosome has 50 - 250 million base pairs.•DNA is found in the mitochondria. •mDNA is only found in the egg. Sperm has no mitochondria so mDNA is passed to offspring from the mother.•One sequence of DNA is a genome or gene.•Unwind all our DNA, it will stretch from the moon and back 6000X.

http://public.ornl.gov/hgmis/gallery/

• Gene: segment of DNA on your chromosomes that determines your traits.

• Trait: characteristics about you. It can be a part or a behavior. You inherited your traits from your parents.

• What is the human genome?

Genetic material of cells…Genetic material of cells…

• GENES – units of genetic material that GENES – units of genetic material that CODES FOR A SPECIFIC TRAITCODES FOR A SPECIFIC TRAIT

• Called Called NUCLEIC ACIDSNUCLEIC ACIDS

• DNA is made up of repeating DNA is made up of repeating monomers called monomers called NUCLEOTIDESNUCLEOTIDES

DNA(Deoxyribonucleic Acid)

A HISTORY OF DNAA HISTORY OF DNA

• Discovery of the DNA double helixDNA double helix

A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)

B. Rosalind Franklin - X-ray photo of DNA.(1952)

C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.(1953)

Discovery of DNA

Rosalind Franklin -

Invented X-ray diffraction photography. Photo used to determine the shape of DNA is spiral.

DISCOVERY OF DNA

James Watson and Francis Crick used the information from Franklin and other scientists to build a 3-D model of DNA.

Won the Nobel Piece Prize in Chemistry in 1961.

Watson & Crick proposed…Watson & Crick proposed…

•DNA had specific pairing between the DNA had specific pairing between the nitrogen bases:nitrogen bases:

ADENINEADENINE – – THYMINETHYMINE

CYTOSINECYTOSINE - - GUANINEGUANINE

•DNA was made of DNA was made of 22 long stands of long stands of nucleotides arranged in a specific way nucleotides arranged in a specific way

called the called the “Complementary Rule”“Complementary Rule”

DNA

DNA stands for –

Functions of DNA:1. Carries the codes to make proteins.

Deoxyribonucleic acid

2.Carries the genetic material that is passed on from the parents to the offspring.

STRUCTURE OF DNAThese three parts form the basic unit of DNA called the NUCLEOTIDE.

phosphate

Sugar (deoxyribose)

Nitrogen baseCan be A, T, C or G

STRUCTURE OF DNASide Pieces(The Rope Part)

Are alternating units of a 5 carbon sugar and a phosphate group. These go down both sides of the molecule

phosphate

Sugar (called deoxyribose)

STRUCTURE OF DNA

Nitrogen Bases (Steps of the ladder) -

The bases are connected to the sugar only !!!!!

1.Adenine - A2.Thymine – T3.Cytocine – C4.Guanine - G

DNA NucleotideDNA Nucleotide

OO=P-O O

PhosphatePhosphate GroupGroup

NNitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)

CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

phosphate

sugar

thymine

adenine

cytocine

guanine

How are the nucleotides held together?

• Nucleotides are held together by covalent bonds between the sugar of one nucleotide and the phosphate of the next.

DNA

DNA Double HelixDNA Double Helix

NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)

““Rungs of ladder”Rungs of ladder”

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

Nitrogenous BasesNitrogenous Bases

• PURINESPURINES

1. Adenine (A)Adenine (A)

2. Guanine (G)Guanine (G)

• PYRIMIDINESPYRIMIDINES

3. Thymine (T)Thymine (T)

4. Cytosine (C)Cytosine (C) T or C

A or G

BASE-PAIRINGSBASE-PAIRINGS

2 Bonds

CG

H-bonds

T A

3 bonds

STRUCTURE OF DNA

One complete turn of the

double helix is 10 base pairs or 10 steps on

the ladder

DNA Double HelixDNA Double Helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

Chargaff’s RuleChargaff’s Rule

• AdenineAdenine must pair with ThymineThymine

• GuanineGuanine must pair with CytosineCytosine

• Their amounts in a given DNA molecule will be about the sameabout the same.

G CT A

Chargaff’s Rule

• Chargaff discovered that the percentage of A and T were equal. The same for C and G. This observation became Chargaff’s rule. This is always the same no matter what organisms.

Genetic Diversity…Genetic Diversity…• Different Different

arrangements of arrangements of NUCLEOTIDESNUCLEOTIDES in a in a nucleic acid (DNA) nucleic acid (DNA) provides the key to provides the key to DIVERSITYDIVERSITY among among living organisms.living organisms.

The Code of Life…The Code of Life…

• The “code” of the chromosome is the The “code” of the chromosome is the SPECIFIC ORDERSPECIFIC ORDER that bases occur. that bases occur.

A T C G T A T G C G G…A T C G T A T G C G G…

DNA is wrapped tightly around histones and coiled tightly to form

chromosomes

See p. 297

How does DNA copy itself?

Purpose: DNA copies itself to ensure that each new cell that is produced in gets the correct number of chromosomes and receives an EXACT copy of the DNA molecule.

Replication must occur before cell division.

• This is called DNA REPLICATION.

• The DNA molecule serves as its own pattern or template so as an exact copy can be made.

Watson and Crick• The model that Watson and Crick where

the nitrogen bases pair suggested a mechanism for DNA to replicate.

Messelson and Stahl• They proved that DNA is semiconservative

by attaching radioactive material to DNA. As the cell divided, they observed the new DNA in each cell and saw that it contained half of the old.

• Semiconservative: contains half of the old strand when DNA is replicated.

STEPS OF DNA REPLICATION

1. Helicase begin to unzip the double helix at many different places. The hydrogen bonds between the bases are broken. Occurs in two different directions.

2. Free floating in the cytoplasm nucleotides pair with the bases on the template. DNA polyermase bonds together the nucleotides. Small segments are bonded together.

3. Two identical strands of DNA result. The DNA will twist back together. DNA is called SEMICONSERVATIVE because it uses an old strand to make a new one.

This results in 2 new identical DNA molecules.

DNA Replication Video

http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=player_embedded

DNA Replication Fork

Point where DNA is split apart to replicate. Forms a Y!

Role of Enzymes• 1. Helicase

unzips the two DNA strands.

• 2. DNA polymerase is the enzyme that joins individual nucleotides to produce a new strand of DNA. Proofreads DNA when finished!

DNA Replication in Prokaryotic Cells

• 1. Proteins binds to starting point.

• 2. Starts at a single point and proceeds in both directions.

Eukaryotic Replication

• Since eukaryotic cells are so much bigger, the replication will start at dozens to hundreds of different places on the DNA.

DNA REPLICATIONWhat if there is a mistake?

There is always a chance that the wrong nucleotide bonds to another. HOWEVER, DNA polymerase is responsible for “reading” the bases and recognizing and replacing damaged or wrong nucleotides. This PROOFREADING allows for only one (1) error in ONE BILLION nucleotides.

DNA Fingerprinting

• When DNA is found at a crime, the DNA is replicated many times to make enough to test. Once they have fingerprinted it, they can compare to find suspect.

• Video

• http://www.bing.com/videos/search?q=dna+crime+scene&view=detail&mid=684167203C024AD0C797684167203C024AD0C797&first=21&FORM=LKVR22&adlt=strict

DNA Fingerprinting

Speed of DNA Replication• In the human cell, 50 nucleotides can

be added every second. It would that several days for replication to occur if the DNA did not start at several spots on the DNA so that it is occurring in many places on the DNA strand.

Transciption – Making of RNA• Transcription – process of copying DNA

to produce a complimentary strand of RNA.

Types of RNAThere are three (3) types RNA:1. Messenger RNA – (mRNA) carries messages from the DNA in the nucleus to the cytoplasm.

2. Transfer RNA – (tRNA) 20 different kinds which are only able to bond with one (1) specific type of amino acid.

Types of RNA

• 3. Ribosomal RNA – (rRNA) major component (part) of the ribosomes

RNA TRANSCIPTION

Transcription – the process by which DNA makes RNA.

Steps in RNA Transcription:1. A special enzyme tells DNA its time to

make RNA.

2. The enzyme tells the nucleotides to only bond with RNA nucleotides.

3. The code letters for RNA are: A, C, G and U.

RNA TRANSCIPTION

4. Process occurs just like DNA replication

--When complete, only a single strand of RNA is formed UNLIKE DNA’s double strand.

--All three types of RNA are formed this way.

--All leave the nucleus and travel out into the cytoplasm.

Transcription Video

• http://www.bing.com/videos/search?q=transcription&view=detail&mid=EE2661D88067BDEFF3E7EE2661D88067BDEFF3E7&first=0&FORM=LKVR8&adlt=strict

RNA TRANSLATIONProtein Synthesis: the formation of a protein using information coded on DNA and carried out by RNA in the assembly of amino acids.

Proteins are:a. Amino acids in chains – 20 kindsb. Made of 10’s or 100’s or 1000’s of amino acidsc. Must be arranged in a specific sequence for each

type of proteind. Function & type of protein is determined by amino

acid sequencee. DNA makes RNAf. RNA orders the amino acids

RNA TRANSLATION

Translation Process:1. mRNA goes to the ribosomes, tRNA goes to the cytoplasm.2. tRNA picks up amino acids& brings them to the ribosome.3. mRNA tells tRNA in which sequence to assemble the proteins.(mRNA is the template!)4. An amino acid chain is a protein.

RNA TRANSLATION

So WHAT??:

RNA makes amino acid chains

Proteins make cells

DNA makes RNA

Amino acid chains make proteins

Go to gslc.genetics.utah.edu/unitsTranslate & Transcribe a Protein and What is a Protein?

Translation

• Groups of 3 nucleotides on the mRNA code for each amino acid to build a protein.

• These groups of 3 are called: CODONS

• The tRNA brings the correct amino acid to the chain.

• You will build your own proteins tomorrow with the mRNA that you made yesterday!

We have been told that DNA is the blueprint for life, BUT what

does that mean?DNA holds the instructions that tell a cell how to construct amino acid chains. That is important because amino acid chains build proteins.

ANDProteins build cells

Steps to Protein Synthesis

• 1. DNA replication – make new DNA

• 2. Transcription – DNA message given to RNA

• 3. Translation – RNA is translated in amino acid chains(protein).

Prokaryotic - Protein synthesis

• Location – cytoplasm

• At the same time.

• Eukaryotic – Protein synthesis

SO, HOW DOES AN AMINO ACID CHAIN GET BUILT?

RNA stands for ribonucleic acidIt differs from DNA in three ways:1. RNA is single stranded.

2. The sugar in RNA is called ribose.3.Uracil is one of the bases in

RNA. There is NO thymine in RNA. This means A goes with U and G still goes with C.

Well, first we have to make something called RNA

DNA DNA ReplicationReplication• Replication: coping of DNA Replication: coping of DNA

• The DNA molecule produces The DNA molecule produces 2 2 IDENTICALIDENTICAL new complementary new complementary strands following the rules of strands following the rules of base pairing: base pairing:

A-T, G-CA-T, G-C

•Each strand of the Each strand of the original DNA serves as original DNA serves as a template for the new a template for the new strand strand

Semiconservative Model

• Replication is called semiconservation because one strand of DNA is used to as a template to make the new DNA.

Steps of DNASteps of DNA ReplicationReplication

1.DNA unzips and the hydrogen bonds between the nitrogen bases pulled apart. The base pairs are separated and are left exposed. This occurs in two different directions. This occurs along hundreds of different places at a time.

. Parental DNA

DNA Template

New DNA

Steps of Replication

2. Free-floating nucleotides are paired up to the free nucleotides. DNA polymerase bond the nucleotides together.

3.Two identical strands result. DNA polymerase checks for mistakes when complete.

DNA Replication

• DNA has 80 million base pairs in a chromosomes. DNA is copied at about 50 base pairs per second. This would take a month if replication did not occur at hundreds of different places at once.

1. Why is replication necessary?

2. When does replication occur?

3. Describe how replication works.

4. Use the complementary rule to create the complementary strand:

A---?G---?C---?T---?A---?G---?A---?G---?C---?A---?G---?T---?

Replication Quiz

1. Why is replication necessary?So both new cells will have the correct DNA2. When does replication occur?During interphase (S phase).3. Describe how replication works.Enzymes unzip DNA and complementary

nucleotides join each original strand.4. Use the complementary rule to

create the complementary strand:

A---TG---CC---GT---AA---TG---CA---TG---CC---GA---TG---CT---A

Replication Quiz

(1961)(1961) Watson & Crick proposed… Watson & Crick proposed…• ……DNA controlled cell function by DNA controlled cell function by

serving as a template for serving as a template for PROTEINPROTEIN structure.structure.

• 3 Nucleotides = a triplet or 3 Nucleotides = a triplet or CODONCODON(which code for a specific AMINO ACID)(which code for a specific AMINO ACID)

See p.303See p.303

• AMINO ACIDSAMINO ACIDS are the building blocks are the building blocks of proteins.of proteins.

DNA DNA TranscriptionTranscription

• DNA can “unzip” DNA can “unzip” itself and itself and RNARNA nucleotides match nucleotides match up to the DNA up to the DNA strand.strand.

• Both DNA & RNA Both DNA & RNA are formed from are formed from NUCLEOTIDESNUCLEOTIDES and and are called are called NUCLEICNUCLEIC acids.acids.

See p.301See p.301

DNA DNA TranslationTranslation

• The cell uses The cell uses information from information from “messenger” RNA “messenger” RNA to produce proteinsto produce proteins

See p.304-305See p.304-305

We will We will discuss details discuss details

of this on a of this on a later datelater date

Transcription/Translation Quiz1. Why is transcription necessary?

2. Describe transcription.

3. Why is translation necessary?

4. Describe translation.

5. What are the main differences between DNA and RNA.

6. Using the chart on page 303, identify the amino acids coded for by these codons:

UGGCAGUGC

1. Why is transcription necessary?Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.

2. Describe transcription.

RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.

3. Why is translation necessary?

Translation assures that the right amino acids are joined together by peptides to form the correct protein.

4. Describe translation.The cell uses information from MRNA to produce proteins.

5. What are the main differences between DNA and RNA.DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.

6. Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGCtryptophan-glutamine-cysteine

AMAZING DNA FACTS…AMAZING DNA FACTS…

• DNA from a single human DNA from a single human cell extends in a single cell extends in a single thread for almost 2 meters thread for almost 2 meters long!!!long!!!

• It contains information It contains information equal to some 600,000 equal to some 600,000 printed pages of 500 words printed pages of 500 words each!!! each!!! (a library of about 1,000 books)(a library of about 1,000 books)

LET’S REVIEW DNA…LET’S REVIEW DNA…LM p.44LM p.44

1.1. List the conclusions Griffith & Avery, List the conclusions Griffith & Avery, Hershey & Chase drew from their Hershey & Chase drew from their experiments.experiments.

2.2. Summarize the relationship between Summarize the relationship between genes & DNA.genes & DNA.

3.3. Describe the overall structure of the Describe the overall structure of the DNA molecule.DNA molecule.

4.4. What are the 4 kinds of bases?What are the 4 kinds of bases?