| A | B |
|---|
| What direction is transcription carried out in? | 5'-3' direction |
| What is the lac operon model? | E. Coli bacteria use three proteins to break down lactose (milk sugar). These three genes are next to one operon (operon is the genes + operator + promoter). This operon is called the lac operon. A regulator gene, located outside of the operon, codes for a protein that prevents RNA polymerase from binding to the promoter region, thus preventing the synthesis of those three enzymes. However, an isomer of lactose will bind to the repressor protein, and change its shape so it doesn't fit with the operator. This allows for the production of the three enzymes. Therefore, if there is no lactose (and therefore no isomers of lactose), the repressor protein will prevent the transcription of the enzymes. If there is lactose, the repressor protein will be inactivated and the enzymes will be produced. Operons are found only in prokaryotes. |
| What is the process of transcription in eukaryotes? | RNA polymerase separates the two strands of the DNA and bonds the RNA nucleotides when they base-pair to the DNA template. RNA polymerase binds to parts of the DNA called promoters in order for separation of DNA strands to occur. Transcription proceeds as nucleoside triphosphates (type of nucleotide) bind to the DNA template and are joined by RNA polymerase in the 5' to 3' direction. Transcription ends when RNA polymerase reaches a termination site on the DNA. When it reaches the terminator, the RNA polymerase releases the RNA strand. |
| What is the sense strand of DNA? | The sense strand is the coding strand and has the same base sequence as the mRNA (with uracil instead of thymine). |
| What is the antisense strand of DNA? | The antisense strand is transcribed and has the same base sequence as tRNA. |
| What do eukaryotic RNA need to remove to form mature mRNA? | Introns |
| What does reverse transcriptase catalyze? | The production of DNA from RNA. This helps to show the aspects of the DNA viral life cycle to that of the AIDS virus (an RNA virus). |
| How is reverse transcriptase used in molecular biology? | This enzyme can make DNA from mature mRNA (for example, insulin) which can then be spliced into host's (for example bacteria) DNA without the introns. Then when the host's DNA is transcripted, proteins like insulin are made. It is important that the DNA created by reverse transcriptase have no introns, because the host does not have the genes (and therefore proteins) necessary to remove the introns. |
