MBG Part Two: Lecture 8 Flashcards
What is a Gene?
In the nucleotide sequence of the DNA
What is mRNA transcript?
The RNA copy of the template DNA strand of the gene
What is a protein?
The purpose of translation: to decode the mRNA and make the functional protein produce of the gene.
In eukaryotes, where does transcription occur?
In the nucleus
Where does mRNA translation occur?
In the cytoplasm
What did Beadle and Tatum discover?
In the 1930s through genetic analysis of nutritional mutants in the fungus Neurospora, these researchers discovered that one gene encoded one discrete polypeptide.
What did Charles Yanofsky and Colleagues discover?
In the 1960s through mutational/biochemical analysis, they discovered that the sequence of nucleotide triplets in the trap gene fo E.coli corresponded to the sequence of amino acids in the TrpA protein.
What is the coding region of Prokaryote gene like?
Uninterrupted
What is the coding region of Eukaryote gene like?
Typical intron interrupted eukaryotic gene.
What re proteins made up of?
Polypeptides
What do amino acids have?
An N terminal, C terminal and a side group
What are the bonds that join amino acids together?
Peptide Bonds
What is the primary structure of a protein?
Its sequence of amino acids
What is the secondary structure of a protein?
Amino Acids cause the primary structure to fold into the secondary structure, such as an alpha helix or Beta Pleated Sheet
(Spatial Organization)
What is there tertiary structure?
The secondary structure can fold further into a tertiary structure
(Overall Folding)
What is the Quarternary Structure?
Two or more polypeptide chains may associate to create a quarternary structure.
(Several Intermediates of polypeptide chain to make functional protein)
What is the Triplet Code?
4^3 = 64 Codons
4 Nitrogenous Bases
3 Codons
Sufficient for the Synthesis of 20 amino acids
What is the genetic code composed of?
Nucleotide Triplets
Out of the 64 triplets, how many specify amino acids and how many specify stop codons?
61 specify specific amino acids
3 specify stop codons
What are the three stop codons?
UAA
UAG
UGA
What is the genetic code considered to be?
Degenerate (some amino acids are specified by more than one codon)
Which two amino acids are specified by only one codon?
Methionine (AUG) and Tryptophan (UGG)
To account for degeneracy, what did Francis Crick predict?
That several tRNAs must exist for certain amino acids, and that some tRNAs must recognize more then one codon.
Why is there degeneracy (more than one codon for some amino acids) in the genetic code?
Base-pairing between mRNA codons and aminoacyl tRNAs is “anti-parallel” but there is flexibility in binding at the 3rd codon position (1st anti-codon position)
What is the 3rd codon position known as?
The Wobble Position.
What is an example of degeneracy?
The codons UCC and UCU both specify serine (there is a change of the nucleotide in the wobble position)
What can happen to tRNAs at the nucleotide level?
They can be post transcriptionally modified and the nucleotides can be substituted for different nucleotide derivatives.
What is inosine?
A adenine/guanine derivative
What can inosine base pair with?
C,U, A giving the tRNA a lot of flexibility in terms of pairing partners.
What is the Wobble Hypothesis?
Non-standard pairings could take place at the 3rd position of a codon.
What kind of chemical bond holds adjacent amino acids together?
Peptide Bonds
