Biology chapter 2 Pop Quiz

The trp operon was originally identified in Escherichia coli. The trp operon has five structural genes: trpE, trpD, trpC, trpB, and trpA. These genes code for proteins which help a cell produce the amino acid tryptophan.

The diagram shows the order of the genes found in the trp operon. The dotted lines represent the DNA nucleotides between the genes.

1. 1. What is an operon?

2. 2. Identify regions X and Y

3. 3. Identify the region to which RNA polymerase binds to

4. 4. Explain how the trp operon functions when tryptophan levels are low

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The following diagram depicts a molecule crucial to the process of protein synthesis

Structure X is known as?

• mRNA

• RNA

• tRNA

• rRNA

Structure Y is a molecular monomer of

• DNA

• Protein

• RNA

• Lipids

A particular DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases. The number of uracil bases in this DNA double helix would be

• 25

• 50

• 100

• 0

Which one of the following events does not occur during repression when tryptophan levels are high in a cell?

• Tryptophan binds to the trp repressor

• Enzymes that produce tryptophan are produced.

• The transcription factor is inhibited from binding to the promoter

• A repressor protein is bound to the operator region of the trp operon

Different cells within an organism have different proteins. In some cases, different proteins can be coded for by the same gene. One gene can code for several proteins because

• of alternative splicing

• there are 20 amino acids

• of the specificity of the genetic code

• genes can alter their sequence during transcription

Which one of the following statements about the structure of a eukaryotic gene is false

• Introns undergo the transcription process

• Exons contain the protein-coding sequence

• A promoter region is found upstream of a gene

• Alternative splicing results in different sets of introns being translated

The monomers comprising the macromolecule vary in their

• A sugar-phosphate backbones

• nitrogen-containing bases

• phosphate groups

• sugar groups.

A portion of the coding strand of a macromolecule has the sequence -TACGTGCTTGAT-. The mRNA strand produced from this coding strand during transcription would be

• TACGTGCTTGAT

• ATGCACGAACTA

• AUGCACGAACUA

• UACGUGCUUGAU

A hydrogen bond is present between

• v and w

• x and y

• 5' to 3'

• y and z