Exam 8: The Inheritance of Multiple Genes

How does gene duplication contribute to evolution?

Match the missing numbers in the following phrase. Relationships between phenotype and genotype become increasingly complex with the involvement of increasing numbers of genes. Consider two genes. When heterozygotes for two genes are mated, there are usually 9 different genotypes and [A] different phenotypes in the offspring. When two gene products are active in the same process or pathway, non-standard phenotypic ratios can occur instead of the usual 9:3:3:[B] ratio. For example, if both gene products A and B are needed for phenotype X to be observed, and the recessive alleles do not make gene products, in a cross between AaBb and AaBb, then [C] offspring will display phenotype X and [D] offspring will not display the phenotype.

What is the purpose of a complementation test?

What term is used for a gene that contributes to more than one phenotype?

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.

Why are lethal alleles usually recessive?

What is a polymorphic gene?

What is the difference between co-dominance and incomplete dominance?

This question is about Mendel's pea experiments. What genotype and phenotype proportions are expected from a cross between two plants that are heterozygous for pea color and shape? The parent plants have round, yellow peas. Please select all that apply.

Genes usually have multiple alleles. Alleles that have the same phenotype can be grouped together. Alleles can also be ranked in an allelic series, such as with agouti, which governs coat color in dogs and other animals. Rank the following alleles for the hypothetical gene C, governing hair color, in order of dominance (most dominant first). There are four alleles: C^r, C^y, C^b, and C^w. Individuals homozygous for these alleles have red, yellow, black, and brown hair, respectively. C^r_ individuals have red hair. Heterozygotes carrying C^y do not have yellow hair. In a cross between homozygous C^b and C^w individuals, ¾ of the offspring have brown hair. -C^w

Coat color in Labrador retrievers is usually yellow, black, or chocolate brown. This is determined by alleles of the E gene and the B gene. Dogs with recessive e alleles (ee) are yellow, even when the B locus is functional. This means that the B gene is epistatic to the E gene.

In the ABO blood system, what genotypes do two parents need to have in order to be able to produce children with all the possible ABO blood types. Please select all that apply.

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

Genes usually have multiple alleles. Alleles that have the same phenotype can be grouped together. Alleles can also be ranked in an allelic series, such as with agouti, which governs coat color in dogs and other animals. Rank the following alleles for the hypothetical gene C, governing hair color, in order of dominance (most dominant first). There are four alleles: C^r, C^y, C^b, and C^w. Individuals homozygous for these alleles have red, yellow, black, and brown hair, respectively. C^r_ individuals have red hair. Heterozygotes carrying C^y do not have yellow hair. In a cross between homozygous C^b and C^w individuals, ¾ of the offspring have brown hair. -(most dominant) = C^r

Fill in the blank. Redundancy is where more than one gene can perform a particular function. If genes A and B are redundant for a particular phenotype, ___/16 offspring from a cross between AABb and aabb would be expected to exhibit the phenotype.

Match the missing words in the following phrase. Dominance is defined by the [A], not the [B], of the [C]. If this is the same as in the [D] for one of the alleles, then that allele is dominant.

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.

Mendel's law of independent assortment suggests that the inheritance of one gene or trait does not influence the inheritance of a separate unlinked trait.

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

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