Deck 8: The Inheritance of Multiple Genes

Question 1

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.

Answer 1

True

Question 2

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.

A) 1/16 YY RR
B) 4/16 yy rr
C) 3/4 yellow peas
D) 1/4 wrinkled peas
E) 1/2 Yy Rr

Answer 2

1/16 YY RR
3/4 yellow peas
1/4 wrinkled peas

Question 3

When considering the inheritance of multiple independent traits, it is often simpler to multiply the probability of each individual trait to determine the probability of the overall phenotype. Assuming inheritance is independent, in a cross between two tall pea plants with yellow round peas and purple flowers, genotype YyRrTtPp, what is the probability that offspring will be tall and have white flowers and produce yellow wrinkled peas? Your answer should be the value of A in the fraction A/256

Answer 3

9
Explanation: The probability that offspring will be tall and have white flowers and produce yellow wrinkled peas is 9/256. For each single trait there is a 3:1 inheritance ratio between the dominant and recessive trait. ¾ of offspring are tall, ¼ have white flowers, ¾ have yellow peas, and ¼ have wrinkled peas. Therefore, the probability of having all these traits is ¾ x ¼ x ¾ x ¼ = 9/256

Question 4

Phenotypes are not always inherited in a predictable Mendelian manner. Which of the following are possible reasons for this? Please select all that apply.

A) A trait may be affected by the environment
B) Traits may be influenced by multiple genes
C) Meiosis is required for Mendelian inheritance
D) Alleles may not be completely dominant

Question 5

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.

Question 6

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

A) In co-dominance, neither allele produces sufficient protein. In incomplete dominance, both alleles make sufficient protein.
B) In co-dominance, both alleles produce sufficient protein. In incomplete dominance, neither allele makes sufficient protein.
C) In co-dominance, the phenotype lies between the phenotypes of the parent alleles. For incomplete dominance, the phenotype of both alleles is seen.
D) In co-dominance, the phenotype reflects both alleles. For incomplete dominance, the phenotype lies between the phenotypes of the parent alleles.

Question 7

Match the phenotypes to their dominance descriptions for the following example. Growth of a heterozygote, Yy, is the same as that of homozygote YY. Homozygote yy does not grow. Yy produces about half as much pigment as YY, and yy does not produce any pigment.

Question 8

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

A) Pleiotropic
B) Epistatic
C) Dominant
D) Complex

Question 9

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.

A) I^AI^B
B) ii
C) I^Ai
D) I^Bi
E) I^AI^A
F) I^BI^B

Question 10

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.

Question 11

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

A) 1 (most dominant)
B) 2
C) 3
D) 4 (least dominant)

Question 12

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

A) 1 (most dominant)
B) 2
C) 3
D) 4 (least dominant)

Question 13

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^b

A) 1 (most dominant)
B) 2
C) 3
D) 4 (least dominant)

Question 14

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^y

A) 1 (most dominant)
B) 2
C) 3
D) 4 (least dominant)

Question 15

What is a polymorphic gene?

A) A gene that has accumulated more than the usual number of mutations.
B) A gene that has more than one common variant
C) A gene that is always heterozygous
D) A gene that has multiple functions

Question 16

Why are lethal alleles usually recessive?

A) Dominant lethal alleles are very uncommon but recessive lethal alleles are very common
B) Lethal alleles prevent an organism reproducing
C) Lethal alleles are usually dominant rather than recessive
D) Recessive lethal alleles can be passed from generation to generation but dominant lethal alleles are not inherited.

Question 17

Which of the following statements about the offspring of a cross between two carriers of a lethal recessive gene are true? Please select all that apply.

A) 50% of live offspring display the heterozygous phenotype
B) The genotypes of the offspring follow the same Mendelian patterns as for crosses not involving lethal genes
C) Where the wild-type gene is dominant, all surviving offspring have the same phenotype
D) Offspring genotypes follow a 2:1 ratio

Question 18

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.

Question 19

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.

Question 20

What is the purpose of a complementation test?

A) To determine whether an organism is homozygous or recessive at a particular locus.
B) To determine whether an allele is dominant or recessive
C) To determine whether lethal alleles are present
D) To determine whether two mutants with the same phenotype have defects in the same gene

Question 21

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.

A) Exposure to toxins
B) Temperature
C) Nutritional conditions
D) Gene regulation

Question 22

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

A) Recessive
B) Dominant
C) Co-dominant
D) Conditional

Question 23

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______

Question 24

What is meant by variable expressivity?

A) When an allele is sometimes dominant and sometimes recessive
B) When penetrance is 100%
C) When members of a group of true-breeding wild-type individuals sometimes exhibit the phenotype of a recessive gene
D) When a group of affected individuals do not all have exactly the same mutant phenotype

Question 25

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

Question 26

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.

A) Gene A is needed for tryptophan synthesis
B) Gene B is needed for tryptophan synthesis
C) Tryptophan is essential for growth in this yeast species
D) Gene A is not needed for tryptophan synthesis
E) Gene B is not needed for tryptophan synthesis

Question 27

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

Question 28

How does gene duplication contribute to evolution?

A) Gene duplication results in an increased number of chromosomes
B) Organisms containing duplicated genes are less fit
C) Gene duplication results in less gene product being made
D) Duplicated genes can be more tolerant of mutations than non-duplicated genes