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Problem 1
Check your understanding of the flow of genetic information through a cell by filling in the blanks.
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a.
b.
c.
d.
e.
f.
g.
h.
i.
Problem 2
Which of the following correctly ranks the structures in order of size, from largest to smallest?
a. Gene–Chromosome–Nucleotide–Codon
b. Chromosome–Gene–Codon–Nucleotide
c. Nucleotide–Chromosome–Gene–Codon
d. Chromosome–Nucleotide–Gene–Codon
- Describe the process of DNA replication: the ingredients needed, the steps in the process, and the final product.
Problem 3
Problem 4
What is the name of the process that produces RNA from a DNA template?
What is the name of the process that produces a polypeptide from an RNA template?
Problem 5
Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA of phage lambda. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have _________. (Explain your answer.)
a. The protein of T2 and the DNA of lambda
b. The protein of lambda and the DNA of T2
c. The protein and DNA of T2
d. The protein and DNA of lambda
Problem 6
A geneticist found that a particular mutation had no effect on the polypeptide encoded by a gene. This mutation probably involved
a. Deletion of one nucleotide
b. Alteration of the start codon
c. Insertion of one nucleotide
d. Substitution of one nucleotide
- Describe the process by which the information in a eukaryotic gene is transcribed and translated into a protein. Correctly use these words in your description: tRNA, amino acid, start codon, transcription, RNA splicing, exons, introns, mRNA, gene, codon, RNA polymerase, ribosome, translation, anticodon, peptide bond, stop codon.
Problem 7
Problem 8
The nucleotide sequence of a DNA codon is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a transfer RNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon?
a. CAT
b. CUT
c. GUA
d. CAU
- A cell containing a single chromosome is placed in a medium containing radioactive phosphate so that any new DNA strands formed by DNA replication will be radioactive. The cell replicates its DNA and divides. Then the daughter cells (still in the radioactive medium) replicate their DNA and divide, and a total of four cells are present. Sketch the DNA molecules in all four cells, showing a normal (nonradioactive) DNA strand as a solid line and a radioactive DNA strand as a dashed line.
Problem 9
- The base sequence of the gene coding for a short polypeptide is CTACGCTAGGCGATTGACT. What would be the base sequence of the mRNA transcribed from this gene? Using the genetic code, give the amino acid sequence of the polypeptide translated from this mRNA. (Hint: What is the start codon?)
Problem 10
Problem 11
Researchers working on the Human Genome Project have determined the nucleotide sequences of human genes and in many cases identified the proteins encoded by the genes. Knowledge of the nucleotide sequences of genes might be used to develop lifesaving medicines or treatments for genetic defects. In the United States, both government agencies and biotechnology companies have applied for patents on their discoveries of genes. In Britain, the courts have ruled that a naturally occurring gene cannot be patented. Do you think individuals and companies should be able to patent genes and gene products?
- A mutation in a single gene may cause a major change in the body of a fruit fly, such as an extra pair of legs or wings. Yet it probably takes the combined action of hundreds or thousands of genes to produce a wing or leg. How can a change in just one gene cause such a big change in the body?
Problem 11
- A chemical called dioxin is produced as a by-product of some chemical manufacturing processes. This substance was present in Agent Orange, a defoliant sprayed on vegetation during the Vietnam War. There has been a continuing controversy over its effects on soldiers exposed to it during the war. Animal tests have suggested that dioxin can be lethal and can cause birth defects, cancer, organ damage, and immune system suppression. But its effects on humans are unclear, and even animal tests are inconclusive. Researchers have discovered that dioxin enters a cell and binds to a protein that in turn attaches to the cell's DNA. How might this mechanism help explain the variety of dioxin's effects? How might you determine whether a particular individual became ill as a result of exposure to dioxin?
Problem 12