encoding and decoding Flashcards
what did Sir Archibald Garrod research?
what were his conclusions?
he researched that genes exert their effects through enzymes
his conclusions were that many inborn errors of metabolism seem to be caused by the absence of particular enzymes. proof that many genes bring about their effects through enzymes was provided by scientists beadle and tatum.
what is alkaptonuria?
it is when some individuals lack the enzyme homogentisic acid oxidase. that breaks down the amino acids tyrosine and phenylalanine, a build up of which leads to an accumulation of homogentinsic acid which makes pee dark brown :/
what is phenylketonuria?
it is the disorder where phenylalanine hydroxylase is absent. this enzyme is involved a metabolic pathway where it converts phenylalanine into tyrosine. if there’s no enzyme then phenylalanine accumulates in the blood leading to high levels which damage the nervous system and lead to mental retardation
what is neurospora crassa?
its a good lab model organism and it can reproduce by asexual reproduction- each spore only has one set of chromosomes and its good for genetic analysis as theres only one allele for each characteristic therefore a recessive mutation is not masked by a dominant allele
what does it mean if something is grown in “minimal medium”?
it means the minimal medium contains all the essential basic nutrients needed for the organism to grow and all the other things are made by biosynthetic pathways dependant upon enzymes such as: -sugar -source of nitrogen -mineral ions -vitamin broth
can you explain the steps of the beadle and tatum experiments?
And what was the purpose of the experiments?
- Grow Neurospora on minimal medium
- Expose cultures to X-rays to induce mutations in DNA
- Isolate spores
- Culture each spore individually in “complete medium” to produce next generation
- Sub-culture and test whether they can still grow on minimal medium
purpose: if a mutant could grow in one of the test tubes they had set up then it showed that it was missing an enzyme to produce a certian amino acid
what is the genetic code?
it is a code that contains all the info required to make protein/ amino acid and it is encoded in the DNA sequence of a gene
how is RNA different from DNA?
- it only has one polynucleotide chain, not 2
- it contains ribose instead of deoxyribose in the backbone
- it has uracil instead of thymine
- DNA is stuck in the nucleus but RNA can go anywhere in the cell
- RNA is much less stable that DNA
what is transcription?
mRNA is accurately copied from the DNA template of the gene. its carried out by an enzyme called RNA polymerase and it makes a complimentary copy of DNA. it is made directionally from the 5’ to 3’
what is translation?
it is when RNA is decoded by the ribosome and converted to a protein with a specific sequence
how many different amino acids are there?
20
what is a codon?
it is a triplet of nucleotides which specify one amino acid
what is it about tRNA that allows them to help ribosomes translate code?
they are “bilingual” as they have one end that can bond to amino acids to take them to the ribosome and another end that can “speak” to DNA (called an anti-codon) so that it knows the correct amino acid to bring
what was the first artificial mRNA synthesised and what would have been its anti-codon?
it was called poly-uracil and the codon was UUU, so the anti-codon wouldv’e been AAA. the tRNA that corresponds to that codon is phenylalanine (Phe)
how does the mRNA know what 3 nucleotides make up a codon?
it knows because of “punctuation”
there are go codons (AUG) and stop codons (UAA, UAG, UGA) to help the mRNA know when to start and stop transcription
