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1. The process of differentiation is when an undifferentiated stem cell begins to selectively express certain genes and turns into a specific tissue type.
2. The promoter is a sequence in the DNA right before a gene. The enzyme RNA polymerase needs to land right before a gene to be transcribed, and the landing strip is the promoter.
3. General transcription factors are small proteins that bind to the promoter and help RNA polymerase to land properly. If the cell needs to create a lot of mRNA, however, it needs the help of specific transcription factors called activators. Unlike the general transcription factors, these specific transcription factors bind upstream of the promoter at sequences in the DNA called enhancer regions.
4. By adding methyl groups to [DNA/histones], gene transcription will be [increased/decreased]. If, instead, acetyl groups are added to [DNA/histones], gene transcription will be [increased/decreased].
5. General transcription factors bind at the TATA box within the promoter, whereas specific transcription factors (activators) bind at a specific combination of distal control elements in the enhancer region.
6. The trp operon is a repressible operon, meaning it is normally transcribing the genes for the synthesis of tryptophan. This suggests that the bacterium normally does NOT have tryptophan available in its environment, because by default, it is creating the enzymes for the synthesis of the amino acid.
7. For each of the following, indicate whether the statement is true or false:
a. During transcription, the entire chromosome is unwound and unzipped: False. Only the portion of the chromosome that contains the gene being expressed is unzipped.
b. The process of transcription involves the enzyme RNA polymerase moving down the entire chromosome and creating a piece of mRNA: False. Yes, the enzyme is RNA polymerase, but no, it is not transcribing the entire chromosome (refer back to part “a”).
c. For a given gene, only one side of the DNA double helix contains the correct code for protein synthesis: True. This is called the template strand.
8. Transcription factors are small proteins that first land on a gene’s promoter, and then help RNA polymerase to align properly on the promoter.
9. A. enhancer region; B. activator proteins; C. RNA polymerase; D. promoter; E. gene; F. DNA bending protein
10. mRNA: CG AUG ACU AGC UGG GGG UAU UAC UUU UAG
11. The lac operon is a(n) [inducible/repressible] operon because it is normally not transcribing the genes for lactose digestion.
12.
13. c. When DNA has methyl groups attached to it, the DNA remains condensed (tightly coiled) and prevents access by the transcription machinery. If the gene cannot be accessed by RNA polymerase, gene expression is decreased.