Unit 8 Review Questions

• If 20 % of the DNA in a guinea pig cell is adenine, what percentage is cytosine? Explain your answer.

• If a non-template DNA to make a protein has the following sequence:

5’ ATGTATGCC 3’What is the sequence of each individual tRNA molecules that are needed to translate this information? How many tRNA’s would the ribosome need for this process?• What are splicosomes? What do they do?

Where would you look for them?

• What is a promoter, and is it located at the upstream or downstream end of a transcription unit?

• What enables RNA polymerase to find the right place on the DNA to start transcribing a gene?

• Suppose X-rays caused a sequence change in the TATA box of a particular gene’s promoter. How would that affect transcription of the gene?

• Do the Interpreting a Sequence Logo activity• Draw a tRNA with the anticodon 3’CGU5’. What

codon would it bind to? What amino acid would it carry? Where would it bind to the codon?

• Cystic fibrosis transmembrane conductance regulator (CFTR) proteins function in cell membranes to allow chlorine ions to cross cell membranes. Individuals with cystic fibrosis have abnormal CFTR proteins that do not allow Cl- ions to move across the cell membrane. Without properly functioning Cl- channels, water builds up inside the cell. You are doing research on a different disease and you hypothesize that it also may be due to a defect in an ion channel in the cell membrane. (go to the next page for questions)

• Diagram or model production of a normal membrane ion channel.

• Based on your understanding of protein synthesis and cell membrane structure and function, propose at least three different alterations that could result in a nonfunctional or missing ion channel.

• What questions would you need to answer to determine which of these alterations may be correct?

• How does the binding of tryptophan and lactose alter the shape and function of the repressor protein?

• Under what conditions is the lac operon active? Why? How does it become active?

• A certain mutation in E. coli changes the lac operon so that the active repressor cannot bind. How would this affect the cell’s production of enzymes for lactose digestion?

• How would a similar mutation affect the trp operon and enzyme production?