Exam 17: From Gene to Protein

In the 1920s, Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals-she used nitrogen mustards-have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation?

A transcription unit that is 8000 nucleotides long may use 1200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

Use the following figure to answer the questions below. -The tRNA shown in the figure has its 3' end projecting beyond its 5' end. What will occur at this 3' end?

Suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5' end of intron 1 (I₁). What might occur?

The following questions refer to this figure of a simple metabolic pathway: -If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on which of the following media?

Changes in a single nucleotide pair within a gene is called

The following questions refer to this figure of a simple metabolic pathway: -A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?

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

During splicing, which molecular component of the spliceosome catalyzes the excision reaction?

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

If a nucleotide substitution switched a U for a C, such that the codon was read as CGC instead of CGU, what would the effect be?

Use the following information to answer the questions below. Yeast is capable of synthesizing the amino acids necessary for survival and can grow on minimal media or enriched media easily. In both conditions, the colonies have a cream colour. The production of adenine is regulated by two genes, ADE1 and ADE2. If either of these genes is defective, adenine cannot be synthesized and the colony will look red (as a result of accumulation of precursors). A common undergraduate lab study is to irradiate yeast cells with ultra violet light from 2-5 sec up to 1-5 minutes, and see what will happen. -If, after irradiating and growing cultures in enriched media, you see some red colonies, what is the easiest way to confirm that the phenotype observed is due to a lack of adenine metabolism?

Use this representation to answer the following questions. DNA template strand 5' ____________________________ 3' DNA complementary strand 3' ____________________________ 5' -Given the locally unwound double strand above, in which direction does the RNA polymerase move?

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

Use the following figure to answer the questions below. -The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?

Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E₁ I₁ E₂ I₂ E₃ I₃ E₄ UTR 3' -Which of the following is a useful feature of introns for this model?

Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?

Garrod's information about the enzyme alteration resulting in alkaptonuria led to further elucidation of the same pathway in humans. Phenylketonuria (PKU)occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe)to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria?

The following questions refer to this figure of a simple metabolic pathway: -According to Beadle and Tatum"s hypothesis, how many genes are necessary for this pathway?

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is