UNIT VI – MOLECULAR GENETICS

IV. MICROBIAL GENETICS – VIRUSES

• Discovery of Viruses 1883 - Adolf Mayer discovered that

__________________________________________________________________ was “contagious” because of the sap

Thought it was caused by a __________ 1890 – Dimitri Ivanowsky passed sap from

infected tobacco leaves through a filter designed to remove bacteria and found that the disease was still transmitted

Bacteria are so small they are getting through the filter

1897 – Martinus Beijerinck discovered that the infectious agent could reproduce & it could not be cultivated on nutrient media in test tubes or Petri dishes

1935 – Wendell Stanley Crystallized the particle & proved _________ were not cells

IV. VIRUSES, CONT• Not organisms; correctly referred to as _________________• Not capable of carrying out life processes without a __________________• Parasites

IV. VIRUSES, cont• Characteristics

Viral genome may be either __________-stranded or ____________-stranded _______ or ________.

Protein coat surrounding virus is known as a _____________ made up of protein subunits called _____________________.

Some viruses are also surrounded by a _______________________ Typically derived from host cell membraneException is Herpes virus, synthesized from nuclear envelope of host cellAide in ____________________. Envelope glycoproteins bind to receptor

molecules on host cellMost viruses that infect animals have envelope

IV. VIRAL INFECTION

IV. VIRAL INFECTION, cont - Reproduction

1. Lytic Cycle – Results in death of host cell.

LYTIC CYCLE

IV. VIRAL INFECTION, cont - ReproductionLYSOGENIC CYCLE

IV. VIRAL INFECTION, cont - Retroviruses

IV. VIRUSES, cont – Animal Viruses

• DNA Viruses Herpesvirus

Herpes simplex I and II Epstein-Barr virus Varicella zoster

Papillomavirus

• RNA Viruses Rhinovirus Coronavirus Ebola virus Influenza virus

IV. VIRUSES, cont – Other Infectious Agent• Viroids

• Prions

V. MICROBIAL GENETICS - BACTERIA

• Genetic Make-up of Bacteria Prokaryotic Single chromosome wrapped in much

less protein than found in euks DNA concentrated in region known as

_____________

• Reproduction Haploid Reproduce asexually through _______________________ Mutations do produce minimal genetic

variation, but bacteria have developed mechanisms for genetic variability through _____________________________ ________________________________

V. MICROBIAL GENETICS - BACTERIA• _______________________

Ability to take up _______________________ from surrounding environment

Used to introduce human genes into bacterial cells to produce human protein

“This is what you will do in lab today”

• ______________________ Use of _________________ to carry bacterial genes from one host cell

to another (phages)

• ______________________ “____________________” One-way transfer of a self-replication piece of DNA called a _______ Donor (male) extends _________, pulls cells together, cytoplasmic

bridge forms, and DNA is transferred

V. BACTERIA, cont

• A Closer Look at Plasmids Bacterium’s ability to produce

plasmids and form pili due to specific piece of DNA known as the ______________________F factor may be integrated into

chromosome, or separate as a piece of plasmid

Contains an origin of replicationCopy of F factor may be

transferred to recipient cell; allow recipient cell to become “male”

• ___________________ – Carry genes for enzymes that destroy antibiotics “This is what you will use in lab

today”

VI. DNA TECHNOLOGY, cont - Extensions

• Gene Cloning Process of preparing

multiple copies of a particular segment of DNA

Plasmid isolated from bacterial cell

Foreign DNA inserted into plasmid

Plasmid returned to bacterial cell; described as recombinant bacterium

Foreign gene is cloned as bacteria reproduce

VI. DNA TECHNOLOGY Techniques• Restriction Enzymes

o Used by bacteria to _________________ viral DNA

o Very specific Each enzyme recognizes a

particular nucleotide sequence Specific points May create _______________

o Used in gel electrophoresis o Also used to form recombinant

DNA Fragments may be pasted

together with _____________

_______________ to form recombinant DNA

VI. DNA TECHNOLOGY, cont - Techniques• Recombinant DNA

DNA containing nucleotides from other sources

Process utilizes _______________ _______________ that make jagged cuts in DNA; creates sticky ends

When DNA from different sources treated with same restriction enzyme, sticky ends “mix & match”

VI. DNA TECHNOLOGY, cont - Extensions

A CLOSER LOOK AT

GENECLONING

USING PLASMIDS

VI. DNA TECHNOLOGY, cont - Techniques• POLYMERASE CHAIN

REACTION (PCR)o In vitro method of

__________________ small amounts or fragmented DNA DNA is heated to

separate the double helix.

Mixture is allowed to cool, DNA primers attach to target

Heat-stable polymerase is used to extend the primers in the 5’–3’ direction.

VI. DNA TECHNOLOGY, cont - Extensions

• GEL ELECTROPHORESISo Separates DNA fragments

based on __________o Restriction fragment analysis

DNA treated with restriction enzymes

Resulting fragments migrate based on size

Produce a pattern characteristic of original DNA and restriction enzyme used

Commonly used in forensics & paternity testing

VI. DNA TECHNOLOGY, cont - Medicine• DNA Fingerprinting

– Collection of a specific pattern of DNA restriction fragments

• Gene Therapy– Replacing a _______________ gene with a _____________ gene (disorders)

• Transgenic Plants– Animals who carry ________________________________ from other species– Created using ___________________

• Transgenic Animals (aka “Pharm” Animals):– Animals who carry _______________ from other species– Goals

• To make animals with better quality traits (better wool, leaner meat, faster maturity)• To produce an animal that serves as a pharmaceutical “factory” by producing large amounts of rare biological

substance for medical use– Example: proteins (ex. blood clotting factor) can be secreted in the animal's milk and can be more easily purified)

– Remove egg cells from a female & fertilize them ___________. Desired gene from another organism is injected into the nuclei of the eggs. These eggs are implanted into a _______________ mother.

VI. DNA TECHNOLOGY, cont - Extensions

• Reproductive Cloning _______________________ ________________________ Process of using unfertilized

egg cell & replacing nucleus with DNA

In 1997, scientists were able to produce first reproductive clone, “Dolly”, by culturing somatic cells in a nutrient-poor medium to de-differentiate them and force them back to totipotency.

Reproductive cloning in animals has enjoyed limited success.