AP Biology: Molecular Genetics

A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. The corresponding codon for the mRNA transcribed is...

3'-UCA-5'

The genetic code is essentially the same for all organisms. Based on this information, one can logically assume which of the following statements to be correct?

A gene from an organism can theoretically be expressed by any other organism.

Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.

A part of the promoter, called the TATA box, is said to be highly conserved in evolution. What might this illustrate?

Any mutation in the sequence is selected against.

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

Continuous transcription of the operon's genes

What correctly describes alternative RNA splicing?

It can allow the production of proteins of different sizes and functions from a single mRNA.

What occurs in translation in eukaryotes to protect the mRNA?

The small subunit of the ribosome attaching to the 5' cap of mRNA

What is true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

The tryptophan operon in some bacteria is a repressible operon that is:

Turned off whenever tryptophan is added to the growth medium

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. What might best give you an answer?

You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.

If you were to observe the activity of methylated DNA, you would expect it to...

be transcriptionally inactive.

What is the role of a molecule that controls a repressible operon?

bind to the repressor protein and activate it

What would be the result of a mutation that inactivates the regulatory gene of a repressible operon in an Escherichia coli cell?

continuous transcription of the structural gene controlled by that regulator

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see?

increased chromatin condensation

Which of the following molecules, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator?

inducer

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that...

many noncoding stretches of nucleotides are present in eukaryotic DNA.

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

ribosomes and tRNA