Question 1

Which of the following is responsible for the discovery of the "one gene=one polypeptide" theory,which says that one gene is responsible for the formation of one polypeptide?

Accepted Answer

Beadle and Tatum discovered the "one gene=one polypeptide" theory.

Question 2

When one gene influences many phenotypic expressions it is said to be:

Accepted Answer

When one gene influences many phenotypic expressions, it is said to be pleiotropic. Pleiotropy occurs when a mutation in a single gene affects multiple phenotypic traits. For example, sickle cell anemia is caused by a mutation in the HBB gene, which results in abnormal hemoglobin. This mutation can cause not only anemia but also other health-related problems such as fatigue, jaundice, and pain episodes.

Question 3

When individuals do not show a trait even though they have the appropriate genotype,the trait is said to exhibit:

Accepted Answer

Incomplete penetrance is the phenomenon in which individuals with a particular genotype do not express the corresponding phenotype. This can occur due to the influence of other genes or environmental factors, which can interact with the gene in question and modify its effects. Incomplete penetrance is commonly observed in genetic disorders, such as polydactyly or Huntington's disease, where some individuals may carry the mutant allele but never develop the disease.

Question 4

Polypeptides are macromolecules comprised of what monomer subunit?

Accepted Answer

Polypeptides are made up of amino acid monomers that are linked together by peptide bonds.

Question 5

Most,but not all,loss of function mutations can be attributed to a:

Accepted Answer

Loss of function mutations are typically recessive because they require two copies of the mutated allele to result in a phenotype. This means that an individual can carry one mutated allele and one normal allele (known as a carrier) and not show any signs of the mutation, but can still pass it on to their offspring. A dominant allele would result in a phenotype when present in only one copy, which is typically not the case for loss of function mutations. Codominant, partially dominant, and incompletely dominant alleles all involve some degree of expression from both copies of the allele, which is also not typically seen in loss of function mutations.

Question 6

Which of the following is a disadvantage for creating inbred animal lines? 1.Increased genetic purity
2)Increased inbreeding depression
3)Increased rate of expression of harmful recessive alleles

Accepted Answer

Creating inbred animal lines increases genetic purity by reducing the genetic variation, but it also increases the rate of expression of harmful recessive alleles, which can lead to inbreeding depression (reduced fitness or viability). Therefore, option 1 is not a disadvantage, but options 2 and 3 are. Thus, the correct choice is E, which includes options 2 and 3.

Question 7

The work of Bateson and Punnett,who studied the combs of chickens,demonstrated that:

Accepted Answer

Bateson and Punnett's study of the combs of chickens demonstrated that the comb type was influenced by two independently assorting genes, indicating that multiple genes can affect a trait. This result provided evidence for the concept of polygenic inheritance.

Question 8

Summer squash color is determined by the interaction of more than one gene.The presence of CC or Cc allele combinations produces a squash that is white in color,and the C allele is epistatic to the G allele.The presence of GG or Gg produces a squash that is yellow in color,and ccgg produces a squash that is green.After two heterozygous squash are crossed one of the offspring is CcGg.What is the color of the offspring squash?

Accepted Answer

The offspring squash with the genotype CcGg will be white in color because the C allele is epistatic to the G allele, meaning the presence of at least one C allele (CC or Cc) determines the squash to be white, regardless of the G allele's presence.

Question 9

Pattern baldness is an example of a genetic trait,often expressed differently in males and females.It is considered a ___________________ trait.

Accepted Answer

Pattern baldness is an example of a sex-influenced trait because it is influenced by sex hormones and expressed differently in males and females. In males, it is often expressed as male-pattern baldness, while in females, it is expressed as diffuse thinning.

Question 10

When two or more genes influence a trait,an allele of one of them may have an overriding effect on the phenotype.When an allele has such an overriding effect,it is said to be:

Accepted Answer

When one gene's expression overpowers another gene's expression, it is referred to as epistasis, and the allele that exerts the overriding effect is referred to as an epistatic allele. Therefore, the answer is choice D, "Epistatic." A dominant allele exerts its effects over a non-dominant allele, but it does not necessarily affect the expression of a completely different gene, and penetrance refers to the proportion of individuals with a specific genotype who exhibit the expected phenotype. "Expressive" is not a common genetics term and is not related to the concept described in the question.

Question 11

The inbreeding coefficient can be defined as the:

Accepted Answer

The inbreeding coefficient measures the probability that two gene copies in an individual are identical by descent from a common ancestor. This probability is based on the amount of inbreeding, or mating between relatives, that has occurred in the individual's ancestry. Option B is incorrect because it refers to the probability that two gene copies are different, which is not related to inbreeding. Option C is incorrect because it refers to gene copies from two different ancestors, which is also not related to inbreeding. Option D is incorrect because it includes all options, but only option A is correct in relation to the inbreeding coefficient.

Question 12

In maize,overall kernel color is controlled by both the endosperm and the aleurone colors.The Y allele produces a yellow endosperm while the homozygous recessive (y/y)state produces a white endosperm.Endosperm color is masked by the presence of a colored aleurone.The R and Pr genes control aleurone color.The combination of Pr and R alleles lead to a purple aleurone.The combination of pr and R alleles lead to a red aleurone.A homozygous recessive (r/r)produces a colorless aleurone,allowing the endosperm color to be expressed.Which allele is epistatic?

Accepted Answer

The R allele is epistatic, as it controls the expression of both the Pr and pr alleles in determining aleurone color. The presence of the R allele can lead to purple or red aleurone, while its absence leads to a colorless aleurone, allowing the endosperm color to show through. The Y allele controls endosperm color, but it is not epistatic as it does not affect the expression of other genes controlling kernel color.

Question 13

In Drosophila that exhibit the Lobe eye mutation,some heterozygous flies have tiny compound eyes,whereas others have large,lobulated eyes and between these extremes,there is a full range of phenotypes.This mutation is said to have:

Accepted Answer

The fact that the Lobe eye mutation displays a range of phenotypes ranging from tiny compound eyes to large, lobulated eyes suggests that it has variable expressivity. Incomplete penetrance would refer to the situation where the mutation is present but the corresponding phenotype is not always expressed, and complete penetrance would refer to the situation where all individuals with the mutation exhibit the corresponding phenotype. Complete expressivity would refer to the situation where all individuals with the mutation exhibit the phenotype to the same degree or extent, which is not the case with the Lobe eye mutation.

Question 14

Bateson and Punnett mated purple sweetpeas with white sweetpeas.F1 hybrids were all purple in color.When the hybrids were mated a ratio of 9 purple :7 white were observed in the F2 generation.Which of the following could best explain this observation?

Accepted Answer

The observed 9:7 ratio in the F2 generation is a classic example of epistasis, where the interaction between two different genes affects the phenotype, leading to a deviation from the typical Mendelian 9:3:3:1 ratio.

Question 15

Geneticists use the _______________________ to analyze the effects of matings between relatives.

Accepted Answer

Geneticists use the inbreeding coefficient to analyze the effects of matings between relatives. The inbreeding coefficient represents the probability that two alleles at any given locus in an individual are identical by descent, meaning they originated from the same ancestral allele. Inbreeding increases the frequency of homozygotes and decreases the frequency of heterozygotes, which can lead to an increased expression of deleterious recessive alleles.

Question 16

The allele for polydactyly is dominant,but most individuals do not exhibit the polydactyly trait.Which of the following explains why this occurs in nature?

Accepted Answer

The allele for polydactyly is incompletely penetrant, meaning not all individuals with the allele will express the trait, which explains why most do not exhibit polydactyly despite it being dominant.

Question 17

The gene that controls Marfan's Syndrome causes abnormal heart defects,the presence of long limbs,the presence of increased height,and many other physical characteristics.It could be said that the gene that controls Marfan's Syndrome is:

Accepted Answer

The gene that controls Marfan's Syndrome is pleiotropic, meaning it affects multiple traits or characteristics.

Question 18

The work of Beadle and Tatum not apply to every gene.Why not?

Accepted Answer

Beadle and Tatum's work described the relationship between genes and the polypeptides they encode, but not all genes code for polypeptides. Some genes code for RNA molecules that do not lead to the formation of polypeptides. Therefore, Beadle and Tatum's work does not apply to these genes.

Question 19

A mutation that actually interfere with the function of the wild-type allele by specifying polypeptides that inhibit,antagonize,or limit the activity of the wild-type polypeptide is known as:

Accepted Answer

A dominant negative mutation is a type of mutation where the mutated gene product not only loses its function but also interferes with the function of the normal, wild-type gene product. This occurs when the protein produced from the mutated allele forms complexes with the normal protein, preventing it from functioning properly. Therefore, the mutated protein acts in a dominant fashion to interfere with the function of the normal protein.

Question 20

Which of the following can control gene activity?

Accepted Answer

The answer of Which of the following can control gene...

Quiz 4: Extensions Of Mendelism