Explore BrainMass

Genetics and Mutations

1. What is the difference between genotype and phenotype?
2. What is the difference between haploid and diploids?
3. What is the difference between a null mutation and a conditional mutation?
4. What are the two types of conditional mutations?
5. What is the difference between a genetic selection and a genetic screen?
6. What is the difference between complementation and recombination?
7. Rank the following mutations in order of reversion frequency: deletion, point mutation, double mutation.
8. Two phages with genotype x+ y - and x- y + are crossed. What are the genotypes of the possible recombinant types? Are any of them wild-type?

Solution Preview

1. What is the difference between genotype and phenotype?

A mutation is any change in the DNA sequence compared with the wild-type strain. A mutant is a strain that harbored the mutation. The phenotype is the observable property compared with the wildtype strain that a mutation may imposed on it. For example, if a cell can synthesize the amino acid leucine, it is denoted with a phenotype of Leu+. If it cannot synthesize leucine, it is denoted as Leu-. The phenotype is indicated by a three letter symbol, the first letter is capitalized, and it is not italicized. Genotype is the genetic composition of an organism. For example, a Leu- cells must have a defective gene that prevent it from synthesizing leucine; it would be denoted as leu-. The genotype is indicated by three lowercase letters that is in italics or underlined. (1)

2. What is the difference between a haploid and a diploid?

A cell that have only a single set of genes are called haploid. The eukaryotic cells have two sets of genes are called diploid. A diploid cell may have one normal copy of a gene and one defective copy. A diploid cell can have two normal copies or two defective copies of a gene. (1)

3. What is the difference between a null mutation and a conditional mutation?

Mutants are classified in several ways based on the condition in which the mutant phenotype is expressed. A null mutation is an nonconditional mutant that showed a mutant phenotype under all condition. For example, a mutant bacteria that require leucine for growth will need it ...

Solution Summary

Mutations are very valuable for the understanding of molecular biology and genetics. A few examples of the knowledge gained from studying mutations are that mutations can help researchers elucidate important biochemical and genetic functions. Mutation can introduce biochemical blocks, which help in identifying biochemical pathways. Mutants can enable one to learn about metabolic regulation and they allow an in vitro biochemical activit that is correlated with an in vivo function. Mutations can also identify the site of action of external agents, and they can indicate the relations between unrelated system. Finally, mutations aid in the identification of the interaction of two proteins.