Suppose a man and a woman are each heterozygous carriers of a mutation causing a fatal hereditary disease not on the RUSP list. Prenatal genetic testing can identify the genotype of a fetus with regard to this disease and can identify fetuses with the disease. What do you think are the three or four most important factors this couple should consider in their decision making about having children?

Consider translation of the following mRNA sequence:

5′-...AUGCAGAUCCAUGCCUAUUGA...-3′

Diagram translation at the moment the fourth amino acid is added to the polypeptide chain. Show the ribosome; label its A, P, and E sites; show its direction of movement; and indicate the position and anticodon triplet sequence of tRNAs that are currently interacting with mRNA codons.

Consider translation of the following mRNA sequence:

5′-...AUGCAGAUCCAUGCCUAUUGA...-3′

What is the anticodon triplet sequence of the next tRNA to interact with mRNA?

Consider translation of the following mRNA sequence:

5′-...AUGCAGAUCCAUGCCUAUUGA...-3′

What events occur to permit the next tRNA to interact with mRNA?

If you were to look up Gaucher disease on the OMIM website, you would see that there are three major types, designated Type I (OMIM 230800), Type II (OMIM 230900), and Type III (OMIM 231000). All three types are mutations of the gene for acid-β-glucosidase, encoded on chromosome 1. Different mutations of this gene produce the three types of Gaucher disease that differ somewhat in their symptoms and disease severity.

Thinking about the production or function of the acid-β-glucosidase enzyme, why do you suppose different mutations of this gene produce differences in symptoms and disease severity?

If you were to look up Gaucher disease on the OMIM website, you would see that there are three major types, designated Type I (OMIM 230800), Type II (OMIM 230900), and Type III (OMIM 231000). All three types are mutations of the gene for acid-β-glucosidase, encoded on chromosome 1. Different mutations of this gene produce the three types of Gaucher disease that differ somewhat in their symptoms and disease severity.

For each mutation, speculate about whether the acid-β-glucosidase enzyme is merely reduced in function or whether its production is eliminated, and explain why.

The diagram of a eukaryotic ribosome shown below contains several errors.

Examine the diagram carefully, and identify each error.

The diagram of a eukaryotic ribosome shown below contains several errors.

Redraw the diagram, and correct each error using the mRNA sequence shown.

Third-base wobble allows some tRNAs to recognize more than one mRNA codon. Based on this chapter's discussion of wobble, what is the minimal number of tRNA molecules necessary to recognize the following amino acids?

Leucine

Third-base wobble allows some tRNAs to recognize more than one mRNA codon. Based on this chapter's discussion of wobble, what is the minimal number of tRNA molecules necessary to recognize the following amino acids?

Arginine

Third-base wobble allows some tRNAs to recognize more than one mRNA codon. Based on this chapter's discussion of wobble, what is the minimal number of tRNA molecules necessary to recognize the following amino acids?

Isoleucine

Third-base wobble allows some tRNAs to recognize more than one mRNA codon. Based on this chapter's discussion of wobble, what is the minimal number of tRNA molecules necessary to recognize the following amino acids?

Lysine

The genetic code contains 61 codons to specify the 20 common amino acids. Many organisms carry fewer than 61 different tRNA genes in their genomes. These genomes take advantage of isoaccepting tRNAs and the rules governing third-base wobble to encode fewer than 61 tRNA genes. Use these rules to calculate the minimal number of tRNA genes required to specify all 20 of the common amino acids.

The three major forms of RNA (mRNA, tRNA, and rRNA) interact during translation.

Describe the role each form of RNA performs during translation.

The three major forms of RNA (mRNA, tRNA, and rRNA) interact during translation.

Which of the three types of RNA might you expect to be the least stable? Why?

The three major forms of RNA (mRNA, tRNA, and rRNA) interact during translation.

Which form of RNA is least stable in eukaryotes? Why is this form least stable?

The three major forms of RNA (mRNA, tRNA, and rRNA) interact during translation.

Compared to the average stability of mRNA in E. coli, is mRNA in a typical human cell more stable or less stable? Why?

The accompanying figure contains sufficient information to fill in every row. Use the information provided to complete the figure.

The line below represents a mature eukaryotic mRNA. The accompanying list contains many sequences or structures that are part of eukaryotic mRNA. A few of the items in the list, however, are not found in eukaryotic mRNA. As accurately as you can, show the location, on the line, of the sequences or structures that belong in eukaryotic mRNA; then, separately, list the items that are not part of eukaryotic mRNA.
5′ ____________________________ 3′

a. stop codon
b. poly-A tail
c. intron
d. 3' UTR
e. promoter
f. start codon
g. AAUAAA
h. 5' UTR
i. 5' cap
j. termination sequence

After completing Problem 17, carefully draw a line below the mRNA to represent its polypeptide product in accurate alignment with the mRNA. Label the N-terminal and C-terminal ends of the polypeptide. Carefully draw two lines above and parallel to the mRNA, and label them 'coding strand' and 'template strand.' Locate the DNA promoter sequence. Identify the locations of the  nucleotide and of a transcription termination sequence.

Define and describe the differences in the primary, secondary, and tertiary structures of a protein.

Describe the roles and relationships between tRNA synthetases and tRNA molecules.

Describe the roles and relationships between tRNA anticodon sequences and mRNA codon sequences.

In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

A doublet without overlaps?

In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

A doublet with overlaps?

In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

A triplet without overlaps?

In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

A triplet with overlaps?

In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

A quadruplet without overlaps?

In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

A quadruplet with overlaps?

Identify and describe the steps that lead to the secretion of proteins from eukaryotic cells.