Question 1

Inferring a genotype from a phenotype can be challenging due to a range of complicating factors that may also affect the phenotype. Which of the following factors can influence phenotype? Please select all that apply.

Accepted Answer

All the options are correct. Variation in a range of environmental factors and cellular factors (such as changes in gene expression) can influence phenotype, explaining why pure-bred organisms are not identical.

Question 2

What is the term for a mutation whose phenotypic effects are only seen under certain environmental conditions?

Accepted Answer

A mutation whose phenotypic effects are only seen under certain environmental conditions is called a conditional mutation. This means that the mutation is not always expressed, but only under specific circumstances or in the presence of certain factors. This can be useful in studying the effects of certain mutations and their interactions with the environment.

Question 3

If fewer than 100% of individuals that are homozygous for a mutant allele exhibit the mutant phenotype, the mutant allele is described as having reduced______

Accepted Answer

The answer of If fewer than 100% of individuals that...

Question 4

What is meant by variable expressivity?

Accepted Answer

Variable expressivity refers to the phenomenon where a group of affected individuals with a particular genotype do not all display the same mutant phenotype. This can be due to differences in the environment, genetic modifiers of the phenotype, or other factors that influence gene expression. Answer A refers to incomplete dominance, not variable expressivity. Answer B refers to the degree to which a gene or genotype manifests as a phenotype in a population. Answer C refers to the phenomenon of incomplete penetrance, where some members of a true-breeding wild-type population carry a recessive allele but do not show the corresponding phenotype.

Question 5

Mutations with more extensive deleterious pleiotropic effects are more likely to be subject to positive selection than mutations with less extensive effects.

Accepted Answer

More extensive deleterious effects are more likely to be associated with negative selection, whereby the frequency of the mutation decreases in the population over time due to the reduced fitness of organisms with the mutation.

Question 6

An experiment is performed with a mutant yeast strain that cannot survive without being given tryptophan. The yeast strain is transformed with a plasmid containing gene A or a plasmid containing gene B. Yeast cells transformed with gene B require supplementary tryptophan to survive, but yeast transformed with gene A can survive in the absence of tryptophan. Which of the following conclusions can be drawn from this experiment? Please select all that apply.

Accepted Answer

The answer of An experiment is performed with a mutant...

Question 7

Phenotypic ratios in offspring are sometimes unexpected, indicating that not all genetic inheritance follows Mendel's principles.

Accepted Answer

Phenotypic ratios from a cross do sometimes give unexpected results as a consequence of a range of different factors. However, individual genes always follow Mendelian patterns of inheritance.

Question 8

How does gene duplication contribute to evolution?

Accepted Answer

Duplicated genes can accumulate mutations without affecting the original gene function, allowing for the evolution of new gene functions or the specialization of duplicated genes for different functions. This process can lead to the creation of new traits or adaptations, ultimately contributing to the diversity of life on Earth.

Quiz 8: The Inheritance of Multiple Genes