In need of help for these two questions. Thank you in advance!
Restriction Enzyme A has the recognition sequence 5′- CTGCAG -3′. Restriction Enzyme B has the recognition sequence 5′- GCGC -3′. Based on this information, you can infer that:
A. Enzyme A will cut the genome into fewer pieces than will Enzyme B.
B. Enzyme A will cut a genome into more pieces than will Enzyme B.
C. Enzyme A will generate DNA pieces with blunt ends and Enzyme B will generate DNA pieces with sticky ends.
D. NONE OF THESE
Which of the following types of gene mutation in a protein-coding gene usually has the least-
severe (i.e., least-deleterious) phenotype?
A. base deletions
B. All generate equally severe phenotypes.
C. missense substitutions
D. nonsense substitutions
For the first question, to determine which restriction enzyme will cut the genome into fewer or more pieces, we need to analyze their recognition sequences.
The recognition sequence of "Enzyme A" is 5′- CTGCAG -3′, which reads the same on both strands. The recognition sequence of "Enzyme B" is 5′- GCGC -3′.
Enzyme A recognizes a 6-base sequence (CTGCAG), while Enzyme B recognizes a 4-base sequence (GCGC).
Since Enzyme A has a longer recognition sequence, it is more specific and will cut the genome into fewer pieces than Enzyme B.
Therefore, the answer to the first question is A. Enzyme A will cut the genome into fewer pieces than will Enzyme B.
For the second question, the types of gene mutations mentioned are base deletions, missense substitutions, and nonsense substitutions.
Base deletions involve the loss of one or more nucleotides in the DNA sequence. This can lead to frameshift mutations, altering the reading frame of the gene and affecting the entire sequence downstream.
Missense substitutions occur when a single nucleotide change results in a different amino acid being incorporated into the protein sequence. The effect of missense substitutions can vary depending on the specific amino acid change and its location in the protein structure.
Nonsense substitutions are point mutations that result in the premature termination of protein synthesis. These mutations introduce a stop codon in the middle of the DNA sequence, causing the protein to be truncated and usually nonfunctional.
Among these options, missense substitutions would usually have the least severe phenotype because they only change one amino acid in the protein sequence, whereas base deletions and nonsense substitutions can have more significant effects on the protein's structure and function.
Therefore, the answer to the second question is C. Missense substitutions usually have the least severe phenotype.
To answer the first question about restriction enzymes A and B, we need to analyze their recognition sequences.
Enzyme A has the recognition sequence 5′- CTGCAG -3′, which means it recognizes the sequence CTGCAG on the DNA strand. Enzyme B has the recognition sequence 5′- GCGC -3′, which means it recognizes the sequence GCGC on the DNA strand.
Since Enzyme A has a longer recognition sequence (6 nucleotides) compared to Enzyme B (4 nucleotides), it is more likely that Enzyme A will cut the genome into fewer pieces than Enzyme B. Each time an enzyme recognizes its recognition sequence, it cuts the DNA strand at a specific point, resulting in DNA fragments.
Therefore, the correct answer to the first question is A. Enzyme A will cut the genome into fewer pieces than will Enzyme B.
Moving on to the second question about the types of gene mutations, let's analyze the options:
- Base deletions: This type of mutation involves the removal of one or more nucleotides from the DNA sequence. It can lead to a frameshift mutation, where the reading frame of the protein-coding gene is altered. Frameshift mutations usually have a more severe impact on the protein's function.
- Missense substitutions: This type of mutation occurs when one nucleotide is substituted with another, resulting in a different amino acid being incorporated into the protein sequence. Depending on the specific substitution, it can have varying effects on protein function, ranging from mild to severe.
- Nonsense substitutions: This mutation occurs when a codon that codes for an amino acid is changed to a stop codon, resulting in premature termination of protein synthesis. This type of mutation often leads to a non-functional or truncated protein.
- All generate equally severe phenotypes: This option states that all types of gene mutations have an equal effect on the phenotype. While some mutations may have similar impacts, it is generally not accurate to claim that all mutations have equal severity.
From the given options, the type of gene mutation that usually has the least severe phenotype is missense substitutions. Although missense mutations can alter protein function, the extent of impact can vary depending on the specific amino acid change and its location within the protein structure.
Therefore, the correct answer to the second question is C. missense substitutions.