Question

silly sentences- mutations practice
you can think about the dna sequence of a gene as a sentence made up entirely of three - letter words. in the sequence, each three - letter word represents a codon, specifying a single amino acid in a protein. examine the following sentence:
thecatwasfatbuttheoldmanwasnot
if you were to split this sentence into individual three - letter words, you would probably read it like this:
the cat was fat but the old man was not
this sentence represents a gene. each letter corresponds to a nucleotide base and each word represents a codon. perform the following sentence mutations. always return to the original sentence for each new mutation. keep your sentences divided into triplets.

1. substitution (point mutation): write out the result of replacing the first letter w with the letter r:
2. insertion (frameshift): write out the result of inserting the letter e after the word but:
3. deletion (frameshift): delete the first the letter in the sentence. write out your result:
4. substitution (point mutation): write out the result of replacing the word but with the word and:
5. insertion (frameshift): write out the result of inserting the word not after the first was:
6. deletion (frameshift): write out the result of removing the word old:
7. insertion (frameshift): write out the result of inserting the letters ea after the letter a in man:

which has greater effect, a frameshift mutation, or a substitution? why?
which has greater effect, deleting a letter, or deleting a whole codon? why?
what might happen to the stop codon in a frameshift mutation?

Explanation:

• Frameshift vs. Substitution: Frameshift mutations (insertion/deletion) shift the reading frame, altering all subsequent codons. Substitution (point mutation) changes only one codon. So, frameshift has a greater effect as it disrupts more of the gene's message.
• Deleting a letter vs. a codon: Deleting a letter (frameshift) shifts the reading frame, affecting all downstream codons. Deleting a codon removes one amino - acid. So, deleting a letter has a greater effect as it disrupts the entire downstream sequence.
• Stop codon in frameshift: A frameshift mutation can cause the stop codon to be either prematurely introduced (if the shift creates a new stop codon earlier) or removed (if the shift changes the stop codon sequence), leading to a non - functional or longer - than - normal protein.

Answer:

1. Frameshift mutation has a greater effect. Because it shifts the reading frame, altering all subsequent codons, while substitution changes only one codon.
2. Deleting a letter has a greater effect. Since deleting a letter (frameshift) shifts the reading frame affecting all downstream codons, while deleting a codon only removes one amino - acid.
3. A frameshift mutation can either prematurely introduce a stop codon (if the shift creates a new stop codon sequence earlier) or remove the stop codon (if the shift changes its sequence), resulting in a non - functional or abnormally long protein.