Gene 303 L2

what are enzymes and what is their relationship to proteins

biological catalyst of biochemical reactions

all enzymes are proteins but not all proteins are enzymes

how does DNA encode proteins

by using RNA as the link

nucleotide sequence in DNA molecule (gene) → transcription → mRNA → translation → amino acid sequence = protein

what did archibald garrod discover

that hereditary diseases associated with defects in cellular metabolism results in inherited defects in ENZYMES

• leads to errors in metabolism

  • 
    

what is Alkaptonuria

hereditary disease

symptoms include black urine

caused by defective enzyme in the pathway leading to the breakdown of the amino acid pheynlalanine

• barely toxic, not life threatening

what substance is in excess causing black urine with Alkaptonuria, what enzyme is mutated to being disfunctional

homogentisic acid is in excess

homogentisic acid 1,2-dioxygenase is the mutated enzyme

Phenylketonuria (PKU)

hereditary disease in phenylalanine break down

causes defects in nervous system development, mental retardation

• specifically damages myelin

treatment is a low phenylalanine diet for individual and mother when the individual is developing

what is built up in excess of phenylketonuria and what is the defective enzyme that causes this

phenylalanine is accumulated, phenylalanine hydroxylase is the defective enzyme

what is a mutation

heritable change in gene or chromosome

• also the process by which such an alteration happens

what is a mutant

a heritable biological entity that differs from wildtype as a consequence of mutation

• mutant chromosome, mutant gene, mutant allele, mutant cell

also a cell or organism in which a mutant allele is expressed

allele

any alternative form of a given gene

what is the typical activity percentage of a mutant enzyme compared to a wildtype enzyme and why

<3%

because activity is dependent on binding site and the shape of it. the mutation causes structural changes to the proteins causing the binding site to change if not disappear completely

missense mutation

alteration in coding sequence of DNA that results in amino acid replacement

affects the structure and might even cause it to be destroyed as it won’t be stable

what is a genotype

the genetic constitution of an organism, a cell, or a virus

what is a phenotype

the observable properties of a cell or organism, which result from the interaction of the genotype and the environment

can genes affect more than one trait

yes, its called pleiotropy

example of this is that 40% of white cats with blue eyes are deaf

• this is because the same gene that controls either coat or eye color, also affects hearing

any trait can be affected by more than one gene

most of the traits are also affected by the environment