Question 1

When both traits are exhibited in the phenotype, it is said that the alleles display

Accepted Answer

Co-dominance occurs when both alleles are expressed in the phenotype, meaning neither is dominant nor recessive. This is different from incomplete dominance, where a blending of traits occurs, and complete dominance, where one allele completely masks the expression of the other. Gene silencing refers to the inactivation of a gene, which is not relevant to the scenario described.

Question 2

The frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

Accepted Answer

The relationship between the high frequency of heterozygosity for the sickle-cell anemia allele and reduced malaria frequency is an example of natural selection. The sickle-cell trait is advantageous in areas with high malaria prevalence because it provides some resistance to the disease. As a result, individuals with the sickle-cell trait are more likely to survive and pass on their genes to the next generation. This leads to an increase in the frequency of the sickle-cell allele in those populations, demonstrating evolution through natural selection.

Question 3

Which of the following calculations requires that you utilize the addition rule?

Accepted Answer

The addition rule is used when calculating the probability of events that can occur in two or more ways. In this case, we are calculating the probability of a child having one of two different genetic disorders, sickle-cell anemia or cystic fibrosis, which can occur in different ways depending on the combination of alleles inherited from the parents. Therefore, we need to use the addition rule to add the probabilities of each possible outcome.

Question 4

(The)________: when two alleles separate from each other and end up in separate gametes.

Accepted Answer

The law of segregation states that during the formation of gametes, the two alleles for a gene segregate from each other so that each gamete carries only one allele for each gene. This segregation of alleles is what leads to the inheritance of traits from parents to offspring.

Question 5

Use the following information to answer the questions below.
A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in this figure.
 
-A certain female's number 12 chromosomes both have the blue gene and number 19 chromosomes both have the long gene. As cells in her ovaries undergo meiosis, her resulting eggs (ova)may have which of the following?

Accepted Answer

During meiosis, each egg (ovum) receives one set of chromosomes, so it will have one chromosome 12 with the blue gene and one chromosome 19 with the long gene, as per the given genetic makeup of the female.

Question 6

In cattle, roan coat colour (mixed red and white hairs)occurs in the heterozygous (Rr)offspring of red (RR)and white (rr)homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Accepted Answer

When two roan cattle (Rr) are crossed, the offspring can be RR (red), Rr (roan), or rr (white), resulting in a 1:2:1 ratio.

Question 7

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?

Accepted Answer

Pleiotropy is the phenomenon where one gene affects multiple seemingly unrelated traits or functions. Cystic fibrosis is an example of pleiotropy, as it affects multiple organs and systems in the body. Choices A, B, D, and E are not applicable to describing cystic fibrosis.

Question 8

Which of the following provides an example of epistasis?

Accepted Answer

Epistasis occurs when one gene masks or affects the expression of another gene. In this case, the "cc" genotype prevents any fur color from developing, regardless of the genotype of other genes involved in fur coloration. This is an example of epistasis.

Question 9

Most genes have many more than two alleles. However, which of the following is also true?

Accepted Answer

While most genes have many more than two alleles, the expression of these alleles may only result in two observable phenotypes. This is often due to incomplete dominance or co-dominance. Option A is false as there can be co-dominance or incomplete dominance, where no allele is truly dominant. Option B is false as many alleles may be present in populations, even if they are not found in a particular individual. Option C is false as some alleles may be neutral or have beneficial effects. Option E is false as having more than two alleles for a gene does not necessarily result in lethality.

Question 10

An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable genetically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?

Accepted Answer

The answer of An obstetrician knows that one of her...

Question 11

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

Accepted Answer

Environmental factors, such as soil pH, can affect the color of hydrangea flowers. In acidic soils, hydrangeas tend to produce blue flowers, while in alkaline soils, they tend to produce pink flowers. Therefore, differences in flower color within a population of hydrangea plants could be due to environmental variability.

Question 12

Phenylketonuria (PKU)is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. The amino acid is not otherwise produced by humans. Therefore, the most efficient and effective treatment is which of the following?

Accepted Answer

The most efficient and effective treatment for PKU is to regulate the diet of the affected persons to severely limit the uptake of the amino acid that they cannot metabolize properly. This is achieved by having the patient follow a special low-protein diet that severely limits the intake of foods containing the amino acid phenylalanine. By limiting phenylalanine in the diet, the buildup of toxic byproducts that can occur in untreated individuals with PKU can be prevented.

Question 13

A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?

Accepted Answer

Designing a test for identifying heterozygous carriers of the allele is the best use of this discovery because it allows for the identification of individuals who carry one copy of the allele (are heterozygous) and therefore have a risk of passing the allele to their offspring. This information can be crucial for genetic counseling and making informed reproductive choices, especially since the homozygous condition is lethal.

Question 14

An individual that has two different alleles for the same trait is said to be

Accepted Answer

An individual that has two different alleles for the same trait is said to be heterozygotic, as opposed to homozygotic, which would indicate that the individual has two identical alleles for a given trait. The other multiple-choice options are not accurate descriptions of an individual with two different alleles for the same trait.

Question 15

Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of approximately 13. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption?

Accepted Answer

The fact that patients with Hutchinson-Gilford progeria exhibit a consistent set of symptoms and phenotype suggests that this disorder is caused by mutation in a single gene. This is further supported by research that has identified a mutation in the LMNA gene as the cause of Hutchinson-Gilford progeria.

Question 16

Visitors at Algonquin Park in Northern Ontario may miss out on the brilliant red colouration of Acer sacchrum in autumn because

Accepted Answer

The most likely reason for visitors missing out on the brilliant red coloration of Acer sacchrum in autumn is that the production of anthocyanin and loss of chlorophyll are responses to environmental cues, such as temperature and daylight hours, and may have already occurred by the time visitors arrive. This is supported by the fact that different regions and microclimates can have different peak times for fall foliage.

Question 17

________ is when a gene on one locus has an influence on the phenotypic expression of an allele at another locus.

Accepted Answer

Epistasis is the phenomenon where a gene at one locus can affect the expression of a gene at another locus. This can result in the masking of the expression of one gene by another.

Question 18

Which of the following is an example of polygenic inheritance?

Accepted Answer

Skin pigmentation in humans is controlled by multiple genes, making it an example of polygenic inheritance. The amount of melanin produced in the skin is influenced by the combined effects of many genes, resulting in a wide range of skin tones. The other options are examples of either single gene inheritance or chromosomal inheritance.

Question 19

Which of the following describes the ability of a single gene to have multiple phenotypic effects?

Accepted Answer

Pleiotropy is the ability of a single gene to have multiple phenotypic effects, meaning that one gene can affect multiple traits. Incomplete dominance refers to a situation in which the phenotype of a heterozygote is intermediate between the two homozygotes, while multiple alleles refer to the existence of more than two forms of a gene in a population. Epistasis refers to the phenomenon in which one gene affects the expression of another gene.

Question 20

An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?

Accepted Answer