Chapter 14.1.1 (Exam 3) Coding Flashcards
Genes Code for Proteins
What is alkaptonuria?
Alkaptonuria, a disease in children caused by a recessive mutant allele
The mutation produced homogentisic acid (HA), turned the urine dark brown
What is homogentisic acid (HA)? And why does it get accumulated?
HA is a breakdown product of tyrosine; it is normally converted to a harmless product by an enzyme
The mutation rendered the enzyme inactive, and toxic HA accumulated
The man who discovered it, Archibald Garrod, concluded that there must be one gene to one enzyme
How did Beadle and Tatum test the one-gene, one-enzyme hypothesis?
Beadle and Tatum used Neurospora to test the one-gene, one-enzyme hypothesis
Why did Beadle and Tatum use Neurospora? What makes it special?
Neurospora is haploid for most of its life cycle, so there are no dominant or recessive alleles
Wild-type Neurospora strains have enzymes to catalyze all the reactions needed for growth
What are mutagens?
Mutations were induced with X-rays as the mutagen—something that damages DNA
Describe the results displayed by the mutant strains of Neurospora.
The mutant strains needed additional nutrients, such as vitamins, to grow
Results suggested that each mutation caused a defect in only one enzyme in a metabolic pathway, confirming the hypothesis
What was the one-gene, one-enzyme hypothesis updated to?
One-gene, one-polypeptide
Do all RNAs make proteins?
No, only mRNA is translated into protein, tRNA and rRNA are not
Why was the one-gene, one-enzyme hypothesis revised to one-gene, one-polypeptide?
Because genes code for polypeptides, not just enzymes
