DNA

DNA Sequencing for $1,000 soon?• Companies doing nanopore DNA sequencing:– Oxford Nanopore (Dr. Hagan Bayley) & Illumina– IBM & 454 Life Sciences (div. Roche): artificial

nanopores (Stanislav Polonsky)– NabSys (from Brown U in Rhode Island)– University of PA (Marija Drndic)

Biotechnology

Key Points

• Genes are a set of instructions encoded by the DNA sequence

• DNA is a Large polymer made from 4 different subunits (adenine, thymine, guanine, and cytosine)

• DNA structure allows it to code for RNA & proteins and be copied easily

Key Points

• Mutation occur spontaneously at low rates; some mutations make no difference, some change the cells or organisms vastly

• The Human Genome project analyzed all of the DNA in a human and will advance our understanding of DNA

• New technology allows us to look at genes and changes in the genes– This will revolutionize medicine

How do we know DNA is the Genetic Material?

• Griffith’s Transformation Experiment

How do we know DNA is the Genetic Material?

Hershey and Chase• Used radioactive labeling

to trace DNA and Protein• Viral DNA was injected

into the cell• DNA is the genetic

material

DNA Structure

• Nucleotides–5 Carbon Sugar, –1 Phosphate–1 Nitrogenous

Base

The Bases

Watson and Crick

• Built a model of the double helix – Two outside strands of alternating deoxyribose

and phosphate– Cytosine and guanine bases pair to each other by

three hydrogen bonds– Thymine and adenine bases pair to each other by

two hydrogen bonds

Structure of DNA• Twisted ladder• Rails of the ladder are represented by the

alternating deoxyribose and phosphate• The pairs of bases (C-G or T-A) form the steps

Chromosome Structure

Semi Conservative Replication

• Parental strands of DNA separate and become the template for the new strand

Prokaryotic and Eukaryotic DNA

• Prokaryotes: What are they?– 1 large circular DNA strand– Some very small plasmids (also circular)

• Eukaryotes: What are they?– Many chromosomes– All are linear

The Central Dogma of Biology

DNA is “copied” complimentary by mRNA

Messenger RNA

mRNA leaves the nucleus to go to the ribosome; meets transfer RNA

that brings an amino acid

The Code

• DNA code is 3-base code

• 3 base code in mRNA is a codon

• We can code DNA or mRNA into Protein

• UUCAGACACGAC

DNA code to Protein

Mutations

• A permanent change to the DNA is called a mutation

• Types of Mutation– Point mutation– Insertion– Deletion

• Mutations to somatic (body) cells are not passed to the next generation

• Mutations to the sex cells are passed to the offspring

1. Point mutation - replacement of one DNA nucleotide with another.–missense mutation - point mutation that

changes a codon so that a different amino acid is specified.Ex. sickle cell anemia

Biotechnology and Applied Genetics

Selective Breeding

• Desired traits of plants and animals are selected and passed onto the offspring

• Often results in inbreeding

Saint BernardRescue dog

HuskySled dog

German Shepherd dogHerding/ service dog

The Latest Research• Siberian geneticists have been breeding silver foxes• They have discovered that there are specific traits,

connected to size, floppier ears, tail bone length, fur color & pattern and behavior like tail wagging that are related to fox-human connections.

• After only 9 generations they have fox that connect with humans the same way as dogs; domestication is in their genes: each generation is tamer (unlike tigers)

Inbreeding

• Two closely related organisms are bred to have desired traits and eliminate undesired traits

• Pure breeds are maintained by inbreeding• A disadvantage is that harmful recessive traits

can be passed along– German Sheppard- hip dysplasia– Dalmatian- deafness– Boxers- high rate of cancer

Test Cross (Remember the Deaf Dalmatian)

How do we do this problem?

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Gene Engineering

• Technology that involves manipulating the DNA of one organism and inserting it into another

• Look it glows green!!

Why do we genetically engineer organisms?

• To study the expression of a gene• To study the cells• To study the development of diseases• Find traits that might be beneficial to humans

Gel electrophoresis

• Separates DNA based on size

• DNA is negatively charged

DNA Tools

• A genome is all of the DNA in the nucleus of the cell

• DNA tools and manipulate DNA and isolate genes from the rest of the genome

Biotechnology

• Genetically engineered organisms that have a gene from another organism are called transgenic organisms– Used for research- mice and fruit flies– Crops- Round-up Ready soybeans– Health- insert functioning genes into a virus or

bacteria and infect the host– Bioterrorism- super anthrax

Plants…

• Genetically engineered cotton resist boll weevil infestation

• Golden Rice- has more vitamin A

• Many plants- (corn, soy and coca)- are Round-up ready and resistant to a common herbicide

Human Genome Project

• Sequenced all 3 billion nucleotides in a human

• 20,000-25,000 genes• 2% of the nucleotides

codes for protein• We are still trying to

find out what the rest does

DNA Fingerprinting• Long stretches of

noncoding regions are unique to each individual

• We can look at these fragments and observe patterns