Lecture 5 Flashcards
What happens to urine when exposed to air
from yellow to brown to black
Who was the first to connect inherited human disorders with Mendel’s laws of inheritance
Archibold Garrod
What is different for alkaptonuria patients
urine contains large amounts of homogentistic acid
What was Garrods hypothesis
- Alkaptonuria patients lack the enzyme necessary for breaking down homogentistic acid
- Lack of the enzyme is due to a defect in a gene
What is the missing enzyme in alkaptonuria patients
Homogentisic acid oxidase
Conclusions from Garrods experiments
-Defects in genetic material can lead to specific diseases which can be inherited
-Mendelian Genetic inheritance can be observed in humans
-Lack of an enzyme is due to a defect in a gene
Beadle and Tatums hypothesis
if they damaged the DNA for one of these enzymes, then the cells would not be able to grow without the particular nutrient
Beadle and Tatums experiments
to test if genes were responsible for specific chemical reactions they irradiated Neurospora with X-rays. They then identified a series of auxotrophic mutants
What are auxotrophs
mutant strains that cannot synthesize a particular molecule required for growth therefore they will only grow if they are supplied with that molecule
Screening for auxotrophic mutants
- Culture individual spores on complete medium
- Transfer to minimal medium (MM) to identify possibly auxotrophs
- Test candiates for growth on MM supplemented with different classes of nutrients (vitamens or amino acids or nucleotides)
- Test candiates for growth on MM supplemented with individual amino acids (or vitamins or nucleotides)
- Identify the amino acid that allows your mutant to grow
How do genes specfiy proteins
-DNA in nucleus but proteins made in cytoplasm
-Genes do not specify proteins directly
-“messenger” required - information transferred from nucleus to cytoplasm
-Messenger is ribose nucleic acid (RNA)
What is transcription
the synthesis of a mRNA molecule using one strand of the DNA as a template such that G pairs with C and A pairs with U. catalysed by RNA polymerase
What is translation
4 letter language of RNA has to be translated into the 20 letter language of the protein
