Genetic Mutations

Question

Mutation as a process that creates genetic variation. Mutation creates variations in protein-coding portions of genes that can affect the protein itself. More often, it creates variations in the switches that control when and where a protein is active and how much protein is made.
For example: lactase is an enzyme that helps infants break down lactose, a sugar in milk. Normally the gene that codes for lactase is active in babies and then turned off at about age four. When people who do not make lactase consume milk, they experience discomfort. But some people have a variation in a genetic switch that keeps the lactase gene active and people who have it can keep milk in their diets even as adults.

Mutations are a source of genetic variation. Mutations that occur in sex cells or gametes, can be passed from one generation to the next. Mutations that occur in somatic or body cells, like a mutation causing skin cancer, will not be passed on. Mutations can be classified as harmful, as is the case of the sickle cell gene, beneficial, or having no impact on the organism at all, neutral.

Most of the mutations in our DNA are naturally-occurring. For example, when a cell divides, it makes a copy of its DNA and sometimes the copy is not perfect. That small difference from the original DNA sequence is a mutation. Mutations can also be caused by exposure to specific chemicals or radiation; mutagens.

There are many different ways that DNA can be changed, resulting in different types of mutation.
Substitution
A substitution is a mutation that exchanges one base for another. A substitution could:
~change a codon to one that encodes a different amino acid and cause a small change in the protein produced. For example, sickle cell anemia is caused by a substitution in the beta-hemoglobin gene, which alters a single amino acid in the protein produced.
~change a codon to one that encodes the same amino acid and causes no change in the protein produced. These are called silent mutations.
~change an amino-acid-coding codon to a single "stop" codon and cause an incomplete protein. This can have serious effects since the incomplete protein probably won't function.
Insertion
Insertions are mutations in which extra base pairs are inserted into a new place in the DNA.
Deletion
Deletions are mutations in which a section of DNA is lost, or deleted.
Question 1
PART A
When DNA replication occurs before meiosis, the original DNA strand CAG TGT TTA TAG is copied into complementary strand GTC ACA GGC ATC. What type of mutation has occurred?
Responses
A deletiondeletion
B insertioninsertion
C inversioninversion
D substitutionsubstitution
Question 2
PART B
When DNA replication occurs before meiosis, the original DNA strand GTC ACA GGC ATC is copied into complementary strand CAG CCG TAG. What type of mutation has occurred??
Responses
A deletiondeletion
B insertioninsertion
C inversioninversion
D translocation

Answer 1

To answer the questions regarding the types of mutations:

Question 1: Part A

Original DNA strand: CAG TGT TTA TAG

Copied (complementary) strand: GTC ACA GGC ATC

To determine the type of mutation that occurred, we first need to examine the relationship between the original strand and the copied strand.

1. The original strand should have a complementary strand that fits the base-pairing rules (A-T, C-G).
2. The original strand provided results in the complementary strand GTC ACA GGC ATC, which appears to align with the original.

Since there is no indication that any segments have been removed or added beyond what is expected in a normal replication process and given that all bases are accounted for and correctly paired, we conclude that there has been no mutation that fits the definitions provided (deletion, insertion, inversion, or substitution). However, if the focus is on the specific pairs, the pairing itself does not highlight a classic mutation type.

Since the copied strand seems correct as per DNA complementarity and base pairing, there likely wasn't a mutation during this replication step, but in relative terms according to your choices, no options reflect this appropriately since standard replication doesn't introduce a classic mutation in this context.

As such, I would address this further but from these choices, the question may not apply a defined mutation accurately without more context on what specifically is being identified. In the context provided, the recognized options do not precisely indicate a mutation type given that substitution, insertion, or deletion isn't implied here.

Thus none apply directly, but if you must choose given this situation:

• Option D (substitution) may indirectly apply since there are no defects in pairing and it follows near expectation but is not a classic definition fit here.

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Question 2: Part B

Original DNA strand: GTC ACA GGC ATC

Copied (complementary) strand: CAG CCG TAG

To analyze this, we look closely at the new complementary strand.

Comparing the bases:

• Original: GTC ACA GGC ATC
• New: CAG CCG TAG

If we align them, we can see:

• GTC corresponds to CAG (which is a substitution)
• ACA corresponds to CCG (again, a substitution)
• GGC corresponds to TAG (another substitution)

There are multiple substitutions involving the change from original codons to new codons that do not preserve the integrity of the original sequence.

Since pairs have been mismatched and altered, each codon represents a substitution from the original strand.

Though technically the changes reflect substitutions, it looks like a broader error or misalignment throughout the copying. There also appears to be a segment loss evident between the original base coding and new sequences (given TAG seems like a loss from earlier coding), thus a deletion is implied may also fit (as a segment is missing) within the reasoning of codon transference.

However, as per your options, the closest match from this situation indicates that:

• Option A (deletion) would be most reflective of the parts lost in pairing through what you've provided.

Hence for Question 2, the most appropriate answer is: A (deletion).