Question

biology exam 8
use the diagram below to answer questions 1 - 5.

1. what type of error is shown above?
2. how is the reading frame affected by this error?
3. suppose a nucleotide was replaced with a different nucleotide. do you think this would have a greater or lesser effect on an organism than inserting a nucleotide that shifts the entire strands order? explain. (2pts)
4. could a frameshift error in a germ cell affect the development of offspring that is exposed to the mutated germ cells? how or how not?
5. could an environmental mutagen cause this error? give two examples to support your answer. (2pts)

Explanation:

1. Type of Error:

• A nucleotide (U) is inserted. Insertion of a nucleotide that is not a multiple of three (since codons are triplets) causes a frameshift mutation.

1. Effect on Reading Frame:

• The reading frame is shifted. Since codons are read in groups of three (triplets), inserting one nucleotide changes the grouping of all subsequent nucleotides. For example, if the original sequence was \(AUG - AAG - GUU - U\) (codons), after insertion (\(AUG - UAA - GGU - UU\)), the codons downstream of the insertion are changed.

1. Effect of Replacement vs Insertion:

• A nucleotide - replacement (a point mutation) would have a lesser effect. In a point mutation, only one codon is affected (e.g., if \(AAA\) (Lys) is changed to \(AAG\) (still Lys) or to \(AAT\) (a different amino acid). But in a frameshift (insertion here), all codons downstream are affected, which can lead to a completely non - functional protein.

1. Effect on Offspring from Germ Cell Frameshift:

• Yes, it could affect offspring development. Germ cells (sperm and egg) pass genetic information to offspring. If a frameshift occurs in a germ cell, the mutated DNA is passed to the zygote. The altered protein (due to frameshift) can disrupt normal developmental processes (e.g., if the protein is involved in cell signaling or structural support during development).

1. Environmental Mutagen Cause:

• Yes, environmental mutagens could cause this. For example, UV radiation can cause errors in DNA replication (which can lead to insertions). Another example is certain chemicals like benzopyrene (found in cigarette smoke). These mutagens can damage DNA during replication or repair processes, leading to insertions (or other mutations like deletions) in the nucleotide sequence.

Answer:

1. Frameshift mutation.
2. The reading frame is shifted, changing the grouping of all subsequent codons.
3. A nucleotide replacement would have a lesser effect. A point mutation affects only one codon, while a frameshift affects all downstream codons.
4. Yes. Germ cells pass genetic material to offspring. A frameshift - mutated germ cell can lead to an altered protein in the offspring, disrupting development.
5. Yes. Examples: UV radiation (damages DNA during replication/repair) and benzopyrene (causes errors in DNA handling processes).