U2 Genetic HARD test questions Flashcards
Do all mutations result in a change in the amino acid sequence?
no, some can be silent mutations
What causes dimers to form in DNA, leading to misshapen DNA, which results in replication and transcription erros?
UV photons
Describe the state of the lac operon system if the level of lactose is low, indicating the activity and state of all major enzymes and proteins found in this system. What changes take place if lactose is suddenly made available as a nutrient to the bacteria?
If lactose levels are low, then the repressor will bind to the operator and transcription of genes will not take place, thus proteins will not be made. The repressor blocks the RNA polymerase. If lactose is present, then a lactose molecule will bind to repressor and will change it shape. It will no longer be able to bind to the operator and will thus allow the RNA polymerase to make proteins and run along the DNA strand.
Describe the state of the trp operon system if the level of tryptophan is high, indicating the activity and state of all major enzymes and proteins found in this system. What changes take place if the tryptophan levels fall?
If trp levels are high, a trp molecule will bind to the repressor and will change its shape. The trp corepressor will bind to the operator and block RNA polymerase from making proteins. If levels fall, corepressor will detach and allow RNA polymerase to produce trp.
In a hypothetical situation, 85 amino acids exist and there are still only 4 nucleotides found in nucleic acid. Calculate the minimum number of nucleotides required to code for this large number of amino acids. What is the maximum number of amino acids your answer would code for?
A minimum of 4 nucleotides are needed to code for 85 amino acids, giving a max amino acid
count of 256 (4^4 = 256)
A molecular biologist isolated two DNA fragments of a genetic sequence that were believed to be the promoter region for a certain gene from a bacterial cell. The biologist subjected the DNA fragments to heat and recorded the temperature at which the double strands pulled apart. DNA helix A unwound at 84 degrees, whereas DNA helix B unwound at 65 degrees. Which of the two strands is most likely to be the promoter? Explain.
DNA helix B would most likely be the promoter because promoter regions contain A & T which are held by double hydrogen bonds.
Non promoter regions are made of A, T, C and G and has higher breaking point because of presence of triple bonds.
It takes less heat to break a double bond in comparison to a triple bond.
