Chapter 16 Flashcards
how did scientists first establish what genes do?
started out using metabolic pathways?
how did scientists use metabolic pathways to figure out what genes do?
they manipulated one step of the metabolic pathway and wherever the next enzyme fails, there will be an accumulation of the previous substrate
who studied what genes do?
Beadle and Tatum
what experiment did Beadle and Tatum do?
they studied metabolic pathways for arginine synthesis
what question did Beadle and Tatum ask?
is there a 1:1 relationship between genes and proteins or does one gene encode all proteins needed for arginine synthesis
what were the steps for the genetic screen used by Beadle and Tatum?
- mutagenize (treat with) a population of cells (with UV or X-rays)
- grow mutagenized cells on media that included arginine.
- transfer to media that lacks arginine, look for cells that fail to grow.
- isolate those cells and study them
what does it mean to have cells that grow on arginine plates but do not grow on plates with no arginine?
those cells have mutations in genes that are used for arginine synthesis
what was the conclusion for Beadle and Tatum’s experiment?
there is a one to one gene and enzyme relationship.
*not for all synthesis but just some.
information in a gene (nucleotides) are converted into what?
amino acids of a protein
in Eukaryotes how is information moved from nucleus and into the cytoplasm?
DNA is made in the nucleus
Protein synthesis happens in the cytoplasm
mRNA connects the molecules
what are the steps of the central dogma
Genes (DNA; information storage) —- transcription ——-mRNA (information carrier) ——-translation ———– protein (do the work of the cell)
how do genotypes relate to phenotypes?
if there is one gene different, the translation will be different making the proteins different, so the animal will appear different
true or false:
not all genes encode a protein. Some end at the mRNA step
true
how many bases does mRNA need?
three
what is a codon?
three bases in mRNA that contain genetic information for amino acid; pair to something on the genetic codon chart
what way do the mRNA read?
5’ to 3’
what is the start codon?
AUG
what are the stop codons?
UAA
UAG
UGA
what is the most abundant codon in humans?
GAA
GAG
= Glutamic acid
silent definition
change in nucleotide sequence that does not change the amino acid sequence by a codon
missense definition
change in nucleotide sequence that changes
nonsense definition
change in nucleotide sequence that results in an early stop codon
frameshift definition
addition or deletion of a nucleotide
steps for using the genetic code
given DNA
1. match to RNA base pairs (A-U, G-C), called transcription
2. match those to the codons in the chart, called translation
