Why do we Study DNA?

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

DNA Karotype

• 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.

• Chromosomes: 23 pairs made up of DNA wind around histones (proteins).

• What is the human genome?

DNA Facts•One chromosome has 50 - 250 million base pairs.•DNA is found in the mitochondria.

•One sequence of DNA is a genome or gene.

*DNA molecules are incredibly long. If all of the DNA from all of your cells wasstretched out into a single thread, it would extend to the moon and back about one million times!

• The human genome is contained in 23 pairs of chromosomes.

• The DNA within the human genome makes up 60,000 to 100,000 genes.

• .• Humans get one complete set of genes

from each parent.• In April 2003, the National Human Genome

Research Institute (NHGRI) celebrates• the completion of the human genome

sequence and the 50th anniversary of the description of the DNA double helix.

• The nucleus, or control centre, of a cell, is where DNA is located.

http://genomics.energy.gov/gallery/chromosomes/gallery-01.html

Karotype

• A display of metaphase chromosomes of a cell arranged by size and centromere positions.

• From these pictures, doctors can study to chromosomes to look for disorders.

Genetic material of cells…Genetic material of cells…

What is the type of organic molecule?What is the type of organic molecule?

• Madeup of DNAMadeup of DNA

• Called Called NUCLEIC ACIDSNUCLEIC ACIDS

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

DNA(Deoxyribonucleic Acid)

How do we know that all of our genetic information comes

from DNA?

• What type of experiment would you design to determine that DNA is the source of all genetic information?

Fredick Griffith’s Experiment

1. Injected mice with two bacteria - one that made them sick and one that didn’t.

2. He boiled bacteria A and then the mice did not get sick.

3. He injected both bacteria A(boiled) and bacteria B into mice and they got sick.

CONCLUDED - Transformation occurred. Bacteria causing bacteria changed the harmless bacteria. Passed on genes somehow.

Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation

• Frederick Griffiths was a bacteriologist studying pneumonia

• He discovered two types of bacteria:– Smooth colonies– Rough colonies

Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation

CONCLUSION:

The smooth colonies must carry

the disease!

Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation

• When heat was applied to the deadly smooth type…

• And injected into a mouse…

• The mouse lived!

• Griffith injected the heat-killed type and the non-deadly rough type of bacteria.

• The bacteria “transformed” itself from the heated non-deadly type to the deadly type.

Griffith’s Experiment with Pneumonia and the accidental discovery of Transformation

Avery, McCarty, and MacLeodRepeated Griffith’s Experiment

Oswald AveryOswald Avery Maclyn McCartyMaclyn McCarty Colin MacLeodColin MacLeod

Avery, McCarty, and MacLeodRepeated Griffith’s Experiment

Avery, McCarty, and MacLeodAdded the non-deadly Rough Type of Bacteria to the Heat-Killed Smooth

Type

CarbohydratesCarbohydrates LipidLipidss

ProteinProteinss

RNARNA DNADNA

To the Heat-Killed Smooth Type, To the Heat-Killed Smooth Type, added enzymes that added enzymes that

destroyed…destroyed…

S-Type S-Type Carbohydrates Carbohydrates

DestroyedDestroyed

S-Type S-Type Lipids Lipids

DestroyeDestroyedd

S-Type S-Type Proteins Proteins DestroyeDestroye

dd

S-Type S-Type RNA RNA

DestroyeDestroyedd

S-Type S-Type DNA DNA

DestroyeDestroyedd

Conclusion:Conclusion:

DNA was the DNA was the transforming factor!transforming factor!

The Hershey-Chase Experiment

Alfred Hershey & Martha Chase

worked with a bacteriophage:

A virus that invades

bacteria. It consists of a

DNA core and a protein coat

DNADNA

Protein coatProtein coat

Protein coats of bacteriophages labeled with Protein coats of bacteriophages labeled with Sulfur-35Sulfur-35

DNA of bacteriophages labeled with Phosphorus-32DNA of bacteriophages labeled with Phosphorus-32

BacteriumBacterium

BacteriumBacterium

PhagePhage

PhagePhage1.1. Hershey and Chase Hershey and Chase

mixed the mixed the radioactively-radioactively-labeled viruses labeled viruses with the bacteriawith the bacteria

The viruses infect The viruses infect the bacterial cells.the bacterial cells.

Hershey - Chase

Injected bacteriophages with radioactive isotopes then placed them with bacteria. The virus injected the bacteria with DNA containing radioactive material. Then tested for the radioactive material.

COCNLUDED: Viruses passed on their DNA to the bacteria.

The Hershey-Chase results reinforced the Avery, McCarty,

and MacLeod conclusion:

DNA carries the genetic code!

However, there were still important details to

uncover…

A HISTORY OF THE STRUCTURE A HISTORY OF THE STRUCTURE OF DNAOF DNA

• Discovery of the DNA double helixDNA double helix

A. Rosalind Franklin - Used X-ray photo of DNA to discover the shape was a double helix. (1952)

B. Watson and Crick - Used Franklin’s work to build the first model of DNA. They figured out the exact structure.

(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 the basic unit of DNA NUCLEOTIDE(monomer).

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) -

2.

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)

phophate

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

Amount of DNA

• Amount of DNA in a sample can be determined by how much UV light is absorbs. DNA absorbs UV light!!!

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 is antiparallel

The two strand of DNA run opposite of each other. The happens because of the structure of the nitrogen bases. To fit together,they must be upside down.

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

• In his experments on several different organisms, 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.

Video of girl burned!!

• United streaming

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.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 contain half of the old.

STEPS OF DNA REPLICATION1. 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

1. DNA helicase breaks the hydrogen bonds between the two strands.

2. Replication occurs at multiple site along DNA called origins of replication. This will cause bubbles.

3. Replication occurs in both directions. This makes it quicker.

4. DNA polymerase bring in new nucleotides to fill match with old strand.

5. One strand is easily replicated, the other is made in pieces because DNA polymerase cannot read the upside down piece. DNA ligase will put the pieces together.

6. DNA polyermase will work it way down DNA strands using old DNA as a template.

7. Once complete DNA polyermase will proofread for mistakes.

Go to DNA replication animationwww.fed.cuhk.edu.hk/~johnson/teaching/genetics/

animations/dna_replication.htm

Okazaki Fragments

Small segments of DNA that are used on the 3’ DNA. DNA ligase puts them together.

http://video.search.yahoo.com/search/video;_ylt=Anvp.VTwI60W.BKoUEpJxR.bvZx4?p=dna+replication&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701

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!

3. Ligase -links together the 3’ DNA strand

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 crime, the DNA I replicated many time to make enough to test. Once they have fingerprinted it, they can compare to find suspect.

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.

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

Why is DNA Replication necessary?

• DNA must copy itself so that each new cell gets a copy of DNA. Replication must occur before cell division.

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?

MUTATIONSChanges in DNA that affect genetic

information

Gene Mutations

• Point Mutations – changes in one or a few nucleotides– Substitution

• THE FAT CAT ATE THE RAT• THE FAT HAT ATE THE RAT

– Insertion• THE FAT CAT ATE THE RAT• THE FAT CAT XLW ATE THE RAT

– Deletion• THE FAT CAT ATE THE RAT• THE FAT ATE THE RAT

Gene Mutations• Frameshift Mutations – shifts

the reading frame of the genetic message so that the protein may not be able to perform its function.– Insertion

• THE FAT CAT ATE THE RAT• THE FAT HCA TAT ETH ERA T

– Deletion• THE FAT CAT ATE THE RAT• TEF ATC ATA TET GER AT

H

H

Sex Chromosome Abnormalities

• XYY Syndrome– Normal male traits– Often tall and thin– Associated with antisocial and behavioral

problems

Chromosome Mutations• Changes in number and structure of entire

chromosomes

• Original Chromosome ABC * DEF

• Deletion AC * DEF

• Duplication ABBC * DEF

• Inversion AED * CBF

• Translocation ABC * JKL

GHI * DEF

Significance of Mutations• Most are neutral

• Eye color• Birth marks

• Some are harmful• Sickle Cell Anemia• Down Syndrome

• Some are beneficial• Sickle Cell Anemia to Malaria• Immunity to HIV

What Causes Mutations?

• There are two ways in which DNA can become mutated:– Mutations can be inherited.

• Parent to child

– Mutations can be acquired.• Environmental damage• Mistakes when DNA is copied

Chromosome Mutations

• Down Syndrome– Chromosome 21 does

not separate correctly.– They have 47

chromosomes in stead of 46.

– Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.

Chromosome Mutations

• Cri-du-chat– Deletion of material on 5th

chromosome– Characterized by the cat-like

cry made by cri-du-chat babies

– Varied levels of metal handicaps

Sex Chromosome Abnormalities

• Klinefelter’s Syndrome– XXY, XXYY, XXXY– Male– Sterility– Small testicles– Breast enlargement

Sex Chromosome Abnormalities

• XYY Syndrome– Normal male traits– Often tall and thin– Associated with antisocial and behavioral

problems

Sex Chromosome Mutations

• Turner’s Syndrome– X– Female– sex organs don't

mature at adolescence– sterility– short stature

Sex Chromosome Mutations

• XXX– Trisomy X– Female– Little or no visible differences– tall stature– learning disabilities– limited fertility