BIO201 Merged Slides 81-177

Lecture 83 · Genetic Information is Converted into · Protein: Alkaptonuria (“black urine”)

Most common in children whose parents were first cousins 12.5% The molecular basis of phenotypes was actually discovered before it was known that DNA was the genetic material.

He linked the · biochemical phenotype · of the disease to an · abnormal gene and a

missing enzyme.

Homogentisic · Acid Oxidase · Neurospora:

An altered gene resulted in an altered phenotype, associated with an altered enzyme. Neurospora haploid (n) recessive alleles.

X-rays, which act as a mutagen prototrophs

(original) converted to auxotrophs (increase).

Some mutant strains could no longer grow on the

minimal medium. One group could grow if

supplemented with the arginine (arg mutants).

arg mutants were grown in presence of various

compounds suspected intermediates in the

synthetic metabolic pathway for arginine,

B & T classified each mutation as affecting one

enzyme or another.

wild-type and mutant cells examined for enzyme

activities.

results confirmed: Each mutant strain was indeed

missing a single active enzyme in the pathway.

Beadle Tatum 1940s · END · Lecture 84 · The Dogma:

Info flows from DNA to RNA to proteins.

How does genetic information get from the nucleus to the

cytoplasm?

What is the relationship between a specific nucleotide · sequence in DNA and a specific amino acid sequence in a · protein?) · THE MESSENGER HYPOTHESIS AND · TRANSCRIPTION: · RNA molecule forms complementary copy of one · DNA strand, moves to cytoplasm serves as template

for protein synthesis.

THE ADAPTER HYPOTHESIS AND TRANSLATION: · Adapter molecule binds a specific amino · acid with one region and recognize a sequence of · nucleotides with another region to translate the · language of DNA into the language of proteins

Transcribing from RNA to RNA

Influenza virus, & poliovirus

HIV

make a DNA copy of their genome

END · Lecture 85 · Transcription:

Initiation begins at promoter -tightly binds RNA Pol

1) Where to start transcription. 2) Which strand to read. 3) The direction to take start from. Part of promoter is initiation site (transcription start). RNA Pol moves 3’ to 5’, synthesis 5’ to 3’, primer Unwinds 20 bp at a time. Transcript antiparallel to DNA template strand. No proof reading error rate 1 in 10,000-100,000

Translation starts before termination in prokaryotes.

Pre-mRNA 1st product of transcription in eukaryotes.

END · Lecture 86 · Genetic Code: · Three mRNA nucleotides form a codon:

which is complementary & antiparallel to corresponding DNA. Genetic code relates codons to their specific AA. ~ Universal & Redundant but not ambiguous some exceptions. Start & Stop

Deciphering the Genetic Code · 1) Carries AA · 2) Associates with mRNA · 3) Binds ribosome · tRNA Translates Nucleotide Language into AA Language

tRNA has 75-80 nucleotides with internal H-bonding.

Conformation of tRNA allows it to bind ribosome.

3’ end of tRNA (CCA) is attached to AA & mid point has anticodon (antiparallel).