An attribute of growth behavior of eight bacteriophage mutants (1 to 8) is investigated in experiments that establish coinfection by pairs of mutants. The experiments determine whether the mutants complement one another (+) or fail to complement (-). These eight mutants are known to result from point mutation. The results of the complementation tests are shown below.

How many genes are represented by these mutations?

Verified step by step guidance

1. Step 1: Understand the concept of complementation testing. Complementation tests are used to determine whether two mutations affect the same gene or different genes. If two mutations complement each other (result in a functional phenotype when combined), they are likely in different genes. If they fail to complement, they are likely in the same gene.
2. Step 2: Analyze the first table (complementation results). Each mutant is tested against every other mutant. A '+' indicates complementation (different genes), while a '-' indicates failure to complement (same gene). Group mutants based on their failure to complement each other.
3. Step 3: Use the second table (deletion mutations) to confirm the gene assignments. Deletion mapping helps identify which mutants fall within the same gene by observing whether the deletion affects the phenotype of the mutant. A '-' indicates the deletion overlaps with the mutation, while a '+' indicates no overlap.
4. Step 4: Cross-reference the complementation groups from the first table with the deletion mapping results from the second table. This helps refine the number of genes represented by the mutations.
5. Step 5: Count the distinct complementation groups (genes) based on the combined analysis of both tables. Each group represents a unique gene affected by the mutations.

Key Concepts

Complementation

Complementation is a genetic phenomenon where two different mutations in a gene can restore the wild-type phenotype when present together. In the context of bacteriophage mutants, if two mutants can complement each other, it suggests that they affect different genes. This concept is crucial for determining how many distinct genes are represented by the mutations observed in the experiments.

Point Mutation

Point mutations are changes in a single nucleotide base pair in the DNA sequence. These mutations can lead to various effects, including silent, missense, or nonsense mutations, which can alter protein function. Understanding point mutations is essential for analyzing the specific changes in the bacteriophage mutants and their implications for complementation tests.

Genetic Mapping

Genetic mapping involves determining the location of genes on a chromosome and understanding their relationships. In this case, the results of the complementation tests can be used to infer how many genes are involved in the observed mutations. By analyzing which mutants complement each other, researchers can map the mutations to specific genes, providing insights into the genetic architecture of the bacteriophage.