8.4 Study Guide Flashcards
Define a codon. How do codons relate to anticodons?
Codons are ordered sets of three ribonucleotide bases that make up mRNA strands and that each code for a specific amino acid during translation. Anticodons are also ordered sets of three ribonucleotide bases that each code for a specific amino acid during translation, but they are instead found as individuals on tRNA molecules and consist of the opposite bases to their corresponding codons, allowing them to bind to mRNA strands and put amino acids carried by the tRNA molecules in order during translation.
Describe start codons and stop codons. Why can mutation of these codons be so detrimental to cells?
Start codons code for the amino acid Methionine, and trigger the beginning of translation and of amino acid ordering when read by rRNA molecules within ribosomes. Stop codons are essentially the opposite, as they terminate translation and amino acid ordering when read by rRNA molecules within ribosomes, though they do not code for any amino acid(s). The mutation of these codons can be so detrimental to cells because they can completely and fully alter the amino acid sequence translated from an mRNA strand and, thus, the protein created from it. This alteration repeated hundreds or thousands of times can severely affect the behavior of a cell, as it would likely be producing the completely wrong proteins for its inner and outer functions.
What are the three primary molecule types required for transcription and translation (besides RNA and DNA)? What are the two primary molecule types that reduce or inhibit transcription and translation?
Besides RNA and DNA, RNA Polymerase, Positive Transcription Factors, and Ribosomes are the three primary molecule types required for the processes of transcription and translation. Oppositely, Negative Transcription Factors and mRNA Destroyers are the two primary molecule types that reduce or inhibit transcription and translation respectively.
Define affinity. Why is it so important to transcription as well as essentially every microbiological process?
Affinity is simply the natural attraction between any two molecules. The force of the attraction is the strength of the affinity. Affinity is essentially one of the fundamental forces of the universe and, therefore, is important to all microbiological processes, but to transcription specifically because the affinity between Positive Transcription Factors and DNA and between RNA Polymerase and DNA allows them to bind together to prepare and perform RNA construction.
Define a mutation. Describe each primary type of mutation (point, silent, missense, nonsense, frameshift).
A mutation is any change in the natural deoxyribonucleotide base sequence of a gene or of a cell’s DNA as a whole. Point mutations are changes in one single base, and are generally divided into three categories: Silent mutations, which have no effect on the amino acid sequence resulting from the gene; Missense mutations, which alter one amino acid within the resulting sequence; and Nonsense mutations, which completely alter the entire resulting amino acid sequence by producing a Stop codon. Frameshift mutations are elongations or reductions (just general changes in length) of the ‘Reading Frame’ of an mRNA molecule, which is the section of the molecule that is ‘read’ during translation and which codes for the resulting amino acid sequence. Frameshift mutations can be either insertions of extra bases in the code or deletions of bases, both of which generally have large effects on the overall amino acid sequence.
Describe the process of translation. How does each of the three RNA types play a part in this process?
Translation is the process by which an mRNA molecule is ‘read’ to produce an amino acid sequence and, thus, a protein using its nucleotide base code. During translation, an mRNA strand is fed into a ribosome, where it is ‘read’ by rRNA molecules within the ribosome. Once a start codon is read, tRNA molecules, each carrying an individual amino acid, are brought into the ribosome and bonded to the mRNA molecule based on the mRNA’s codons and the tRNAs’ corresponding anticodons. rRNA molecules then remove the amino acids from the tRNA molecules and string them in the same order, binding them into a primary protein structure that is then moved out of the ribosome. After a tRNA molecule is relieved of its amino acid, it is moved to the end of the ribosome and unbonded from the mRNA by the rRNA molecules, allowing it to be used again for a future translation.
Using a codon chart, translate this mRNA sequence into an amino acid sequence: CGGU AUG UAG CGU GGA CAA GAU UGA UCGAU
Beginning with the start codon and ending with the stop codon, the mRNA sequence can be split like this: AUG | UCG | CGU | GGA | GAU | UGA
This mRNA sequence can then be translated to: Met | Ser | Arg | Gly | Asp | Stop
How do variables like concentrations of positive and negative transcription factors as well as affinities between molecules regulate gene expression in cells?
The concentration of positive transcription factors and gene expression have a direct relationship, as more positive transcription factors means more transcription, which means more translation. Affinities between positive transcription factors and DNA as well as affinities between RNA Polymerase and DNA also have direct relationships with gene expression, as higher bonding rates mean higher transcription rates, which mean higher translation rates. Conversely, the concentration of negative transcription factors and gene expression have an indirect relationship, as more negative transcription factors preventing transcription means less transcription, which means less translation.
Identify whether each of the following mutations is a point mutation or a frameshift mutation. Explain, if it is a point mutation, whether it is silent, missense, or nonsense, and explain, if it is a frameshift mutation, whether it is an insertion or a deletion:
1. AAG - CGC - AGC - UUA –> AAG - CGA - AGC - UUA
2. AAG - CGC - AGC - UUA –> ACG - CGC - AGC - UUA
3. AAG - CGC - AGC - UUA –> AAC - GCG - CAG - CUU - A
- Point Mutation (one base replaced with another); Silent Mutation (CGC and CGA both code for Arginine)
- Point Mutation (one base replaced with another); Missense Mutation (AAG codes for Lysine, while ACG codes for Threonine)
- Frameshift Mutation (Reading Frame messed up); Insertion (of a cytosine base)
