Milestones in molecular biology Flashcards
What is a phage (bacteriophage)
It is a virus that infects and replicates within bacteria and archaea.
Who is Barbara McClintock
She won a Nobel Prize in 1983
Transposition of “jumping genes” Ac (Activator) /Ds (Dissociation) elements in maize (Zea mays)
Showed that gene expression was controlled
Regions on the short arm of Chromosome 9 studied by McClintock
She used a female which had recessive alleles but she got strange results
double fertilisation
the repair of the DS breaking point by activator gene can cause colour.
Name some model organisms and why they are good
Escherichia coli
Saccharomyces cerevisiae
Mus musculus
Caenorhabditis elegans
Arabidopsis thaliana
Drosophila melanogaster
Aspergillus nidulans
Danio rerio
increased standardisation of results
Name the scientists working on E.coli and The lac operon
Francois Jacob and Jacques Monod
What is a Lac operon?
An operon or a group of genes with a single promoter that encode genes for the transport and metabolism of lactose in E.coli and other bacteria.”
the Lac operon functions in E coli
this is the Lac operon it has three structural genes Lac Z lack Y and Lac a.
Lac Z encodes the protein beta galactosidase
Lac y encodes the enzyme permease
Lac a encodes the protein transacetylase
all three of these proteins work together to help the cell bring in and break down lactose when it’s available in the environment. lactose is a sugar that the cell can use
for energy and growth.
These genes all share a promoter and an operator
further Upstream of the Lac operon there is the regulatory Gene lac I which encodes for an active repressor.
the cell wants to be able to break lactose down when it’s present so expression of these genes is necessary.
when lactose is not present it would be a waste of the cell’s energy.
when lactose is absent the Laci repressor is active it binds to the operator and prevents RNA polymerase from binding to
the promoter this limits transcription of the Lac genes in this state the operon is said to be repressed.
when lactose is present in the cell the low concentration of metabolizing proteins that are always available start to convert lactose into allolactose, this allolactose acts as an inducer binding to the Lac I repressor making it inactive
the repressor cannot block The Binding of RNA polymerase therefore transcription of the structural genes can occur this
means that the Lac proteins are produced
in this state the operon is said to be induced by the presence of lactose
What is lac I?
It is a regulatory gene preceding the lac operon. lacI is responsible for producing a repressor (R) protein. In the presence of allolactose, a binary complex is formed between allolactose and the repressor that makes binding of the repressor to the operator region impossible.
What is IPTG?
IPTG (Isopropyl ß-D-1-thiogalactopyranoside), is a molecular biology reagent (sugr). This compound is a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lac operon and it is therefore used to induce protein expression where the gene is under the control of the lac operator.
Describe lacZ as a reporter?
The E. coli LacZ gene is often used as a reporter gene since it produces a blue product once it is cleaved by the β-galactosidase enzyme. This ‘reports’ whether or not the gene is expressed by the bacteria when grown in a compatible substrate (such as X-gal).
What did Fred Sanger do?
2 Nobel Prizes (1958, 1980)
dideoxy ”Sanger” sequencing and the amino acid structure of insulin.
What did Har Gobind Khorana do?
working out the genetic code
Nobel Prize 1968
First chemical synthesis of oligonucleotides
Synthetic oligonucleotides used to work out genetic code
Used PCR before it was “discovered” by Kary Mullis to synthesize genes
What did Kary Mullis do?
Nobel Prize 1993 for PCR
What did Hamilton O. Smith and Daniel Nathans do?
Nobel Prize 1978
Discovered Endonuclease R, later called HindII, which cuts the sequence GTCGAC
This was the first of hundreds of restriction enzymes and sequence specificities to be discovered
Prokaryotic immune system
What did Chalfie, Shimomura and Tsien do?
Carefully mutagenised versions of
G F P and m R F P
have been engineered which fluoresce with various emission wavelengths.
2008 Nobel Prize for Chemistry!
What did (L-R) Jennifer Doudna and Emmanuelle Charpentier do?
Recent developments in genome editing using CRISPR-Cas9
Prokaryotic immune system
Nobel Prize 2020
