Post Mendelian Genetics

Model organsim: Drosophila melanogastor (fruit fly)

-Discovered genes are located on chromosomes.
- some genes are located on the same chromosome (linked genes)
-found sex linked genes by studying eye color in fruit flys
- discovered crossing over and genetic recombination (cross over events unlink linked genes)

model organsim: Tenebrio moliotor (beatle)

Discovered sex chromosomes
Found that males only have XY and females have XX

Distance between two linked genes depends on percentage of recombinant offspring

The farther apart two genes are, the higher change they have of being separated during crossing over

More than one allele for one gene are dominant over other so both are seen in phenotype

(AB blood type)

No alleles are completely dominant

(flowers)

Environmental conditions help determine expression of genotype

Some animals fur changes color based on temperature

When more than one gene contributes to a genotype

eye color, skin color, height

dates: 1903

Showed that Mendel's concepts of segregation and independent assortment could be explained through meiosis

date: mid 1900s
model organism: T2 virus, e coli

Studied what genes were made of. Knew chromosomes contained DNA and proteins.

Found that DNA was genetic material

date: early 1900s
model organism: Alkaptonuria

studied genetic diseases. He knew that metabolic pathways were a series of many smaller reactions catalyzed by enzymes. Hypothesized that if an enzyme wasnt working, there was an accumulation of the substrate which was secreted from body, causing symptoms of disease.

Discovered:
-genes were linked to proteins/coded proteins
-biochemical basis of genetic diseases

mid 1900s
model organism: Neurospora crassa (bread mold)

Wanted to know what genes did by making them defective by exposing them to alot of xrays to create mutations

Pin pointed how certain mutations effect products

Craeted One Gene One Enzyme Hypothesis which says genes contain instructions for making proteins
Later changed to One Gene One Polypeptide hypothesis since not all proteins are enzymes

date: mid 1900s
model organism: eukariotic cells

wanted to know how genes go to proteins (how proteins are synthesized)

mRNA hypothesis: mRNA acts as link from RNA to protein

mid 1900s
model organism: e coli

hypothesized that if mRNA exists, there must be an enzyme to synthesize it. Called it RNA Polymeraze.

Knew ribonucleotides were soluble in acidic solution and RNA would form a percipitant. They took each protein from e coli and saw if it would form a percipitant. If one formed, it was RNA Synthaze, which did happen.

First to articulate Central Dogma of Molecular Biology
(explains unidirectional flow of information in cells)
DNA --> RNA --> protein

Chargoff's Rule:
Ratio of A to T and G to C are almost equal
#purins = #pyrimidines

First to model DNA structrue

hypothesized that combinations of 3 nuceotides (codons) specified which amino acid

model organism: T4 virus
created mutations in DNA to see if genes would still function.

When adding/removing codons, genes still worked
When adding/removing just 1 base from a codon, the gene broke.

Discovered that genetic code is read in triplets

made protein form artificial RNA and deciphered them.

First to decipher codons.
Found there is AUG at beginning of EVERY protein