MGY200 Scientists Gregor Mendel

Gregor Mendel

Law of Dominance, Law of Segregation, Law of Independent Assortment

Edmund Beecher Wilson

Chromosomes are physical element transmitting hereditary characteristics:

1. # of chromosomes are constants between cells in a species

2. Meiosis = constancy of chromosome # through generations = offspring chromosome number stable

Walter Sutton

Chromosomes exist in pairs (one from each parent)

Chromosome pairs synapse together

Each pair orients with spindle and each other

Nettie Stevens

Chromosomes of different sexes are not the same → Y = accessory chromosome

Male = XY, Female = XX

Estrella Eleanor Carothers

A variable autosome from the paternal genomes that is visibly different from its maternal autosome partner.

Both segregation patterns happen approximately the same frequency.

Different chromosomes segregate independently of one another during meiosis

The Boveri's

the chromosomes pairs are of distinct character and to get a fully functional organism requires the correct combination of chromosome

Sturtevant

1st genetic map

1. Things that encode these traits are physically linked on the X-chromosome

2. The frequency of the double mutants arise is proportional to their relative distance on the X-chromosome

Beadle + Tatum

Instead find genes responsible for specific products from biochemical pathways

Genes → pathway products

Importance: 1st human-generated auxotrophic mutant

Rescued a lethal phenotype

Federick Griffith

found multiple types of streptococcus and hypothesized that one type could transform into the other type

1. Rough: Benign → no protective capsule = immune response

3. Smooth: Virulent → protective capsule = no immune response

Oswald Avery

DNA is the transforming principle...

Purifying the "transforming substance" = elemental composition was nucleic acid (not amino acids) = DNA

Fred Sanger

linear structure of peptide chains (primary protein structure) - identified 2 insulin chain sequences

Linus Pauling

inferred the a-helices and B-sheets (secondary protein structure)

Alfred Hershey & Martha Chase

proved Avery right...

Lytic cycle: making more phage → cell breaks = releases phage

Lysogenic cycle: phage DNA integrated into genome

Rosalind Franklin & Raymond Gosling

x-ray crystallography → Photography 51, x-ray crystallographic image of DNA

Maurice Wilkins

Wilkins showed photograph 51 to Watson and Crick, who recognised the structure

James Watson & Francis Crick

Watson and Crick win = correct model = nobel prize

Wilkins also awarded nobel prize

Vernon Ingram

Used the defect in Sickle Cell Anemia = specific protein change

A DNA mutation = this protein change

DNA codes for protein

Paul Zamecnik

Cell free assay to figure out where proteins are made

Used homogenized liver + radioactive lysine = fractionate cellular components

Cellular components that were radioactive: ribosomes

Francis Crick

Central Dogma

DNA → RNA → Protein... NEVER protein → DNA or RNA

Can have RNA → DNA

The RNA Tie Club

20 members to identify how protein was synthesized from genes

George Gamow

Part of RNA tie club - inferred the genetic code is triplet

Seymour Benzer

found 2 classes of rough phage mutants → 1 & 2

R2: mottled plaques

Hypothesis: mixing 2 different R2 mutants = co-infect the K strain = might recombine into a page = could kill the K strain

first fine map → tracks new mutations for the same gene

Leslie Barnett, Francis Crick, & Sidney Brenner

used r// assays with a mutagen, proflavine, that changes one base pair = lots of r// mutants

Add or remove 3 = rescue the reading frame

Genetic code was redundant → multiple codons code for same amino acid (degenerate)

Johannes Heinrich Matthaei & Marshall Nirenberg

The poly-u RNA template = poly-phenylalanine protein

UUU=PHE

Philip Leder & Nireberg

working on making more (different) synthetic RNA to test more codons

Har Gobind Khorana

also working to create synthetic RNA and decoded the genetic code simultaneously

Herbert Boyer

EcoRI in e.coli that cuts a specific sequence = sticky ends

Hind3 and EcoRI destroy foreign DNA - recognition sequences are in the DNA of the bacterium (not in their genome)

Sticky ends = ligation of 2 DNA pieces with reverse complement

Stanely Cohen

plasmid DNA → plasmids are independent circles of DNA, not in the bacterial genome

Plasmids could confer antibiotic resistance to certain antibiotics = R factor

Different plasmids could have different R factors → can transfer

1. Boyer + Cohen

2. Robert Swanson

1. cut and recombine a plasmid

2. new medicines with recombinant DNA (with Boyer)