26. Nucleic Acids and Protein Synthesis

The following is a segment of the template strand of human BRCA1 gene:

TGG AAT TAT CTG CTC TTC GCG

b. Write the three-letter and one-letter abbreviations for the corresponding peptide segment.

What is the effect of a deletion mutation on the amino acid sequence of a polypeptide?

How is protein synthesis affected if the normal base sequence TTT in the DNA template strand is changed to TTC?

Consider the following segment of mRNA produced by the normal order of DNA nucleotides:

ACA UCA CGG GUA

a. What is the amino acid order produced from this mRNA?

Consider the following segment of mRNA produced by the normal order of DNA nucleotides:

ACA UCA CGG GUA

b. What is the amino acid order if a point mutation changes UCA to ACA?

 A polypeptide contains 36 amino acids. How many nucleotides would be found in the mRNA for this polypeptide?

A point mutation changes a codon in the mRNA for an enzyme from GCC to GCA. Why is there no change in the amino acid order in the protein?

In sickle-cell anemia, a point mutation in the mRNA for hemoglobin results in the replacement of glutamate with valine in the resulting hemoglobin molecule. Why does the replacement of one amino acid cause such a drastic change in biological function?

The following is a segment of the template strand of human BRCA1 gene:

TGG AAT TAT CTG CTC TTC GCG

c. If there is a point mutation in the fourth nucleotide triplet and A replaces G, what is the change, if any, in the amino acid sequence?

Answer the following questions for the given section of DNA:

c. Write the three-letter symbols for the amino acids that would go into the peptide from the mRNA you wrote in part b.

Suppose a mutation occurs in the DNA section in problem 17.89, and the first base in the parent chain, adenine, is replaced by guanine.

c. Write the three-letter symbols for the amino acids that would go into the peptide from the mRNA you wrote in part b.

Suppose a mutation occurs in the DNA section in problem 17.89, and the first base in the parent chain, adenine, is replaced by guanine.

a. What type of mutation has occurred?

Match each of the following processes (1 to 5) with one of the items (a to e):

5. reverse transcription

a. amino acids are linked together

b. RNA template is used to synthesize DNA

c. helicase unwinds DNA

d. genetic information is transferred from DNA

e. sticky ends join new DNA segment

Suppose a mutation occurs in the DNA section in problem 17.89, and the first base in the parent chain, adenine, is replaced by guanine.

d. What effect, if any, might this mutation have on the structure and/or function of the resulting protein?

Consider the following portion of mRNA produced by the normal order of DNA nucleotides:

5'CUU|AAA|CGA|GUU3'

c. Write the amino acid sequence if a mutation changes CGA to AGA. Is this likely to affect protein function?