Question 1

Personalized genome sequencing is MOST easily justified in situations in which there are:

Accepted Answer

Personalized genome sequencing is most easily justified when there are few genetic risk factors with large effects. In these cases, personalized genome sequencing can potentially identify individuals who are at a high risk for certain genetic disorders, and enable effective preventative measures and treatments to be implemented. However, when there are many genetic risk factors with small effects, it becomes more difficult to accurately predict an individual's risk for a particular disorder, and the benefits of personalized genome sequencing become less clear. Additionally, insurance policies or research grants may not necessarily be available or sufficient to cover the cost of personalized genome sequencing, making it a less justifiable option in these situations. Similarly, while lifestyle choices can play a role in minimizing risk for certain disorders, they may not necessarily be sufficient to outweigh the potential drawbacks and uncertainty associated with personalized genome sequencing.

Question 2

According to the graph from Figure 18.10, shown below, which complex trait shows very little influence from a genetic component?

Accepted Answer

The answer of According to the graph from Figure 18.10,...

Question 3

One hope of personalized medicine is that:

Accepted Answer

Personalized medicine aims to tailor medical treatment to the individual characteristics of each patient, including using an individual's genetic information (genotype) to predict how they will respond to certain medications, thereby avoiding harmful side effects.

Question 4

Fraternal twins arise from two different fertilized eggs and are called _____ twins.

Accepted Answer

Fraternal twins arise when two different eggs are fertilized by two different sperm, resulting in two genetically distinct embryos. Therefore, they are also called dizygotic twins. Monozygotic twins, on the other hand, arise from a single fertilized egg that splits into two embryos, resulting in twins with identical genetic material.

Question 5

Genetic variation that affects a hypothetical complex trait has the property that 1/2 of the genes have a relative effect of size 1, 1/4 of the genes have a relative effect of size 2, 1/8 of the genes have a relative effect of size 3, and the remaining 1/8 of the genes have a relative effect of size 4. What is the average relative effect size of the genes?

Accepted Answer

The answer of Genetic variation that affects a hypothetical complex...

Question 6

Twin studies have been used to assess the relative importance of "nature" versus "nurture" in determining variation among individuals for complex traits. Which of the following statements is TRUE?

Accepted Answer

Twin studies have shown that autism and clinical depression have a significant genetic component.

Question 7

Consider Figure 18.11, below, which shows the incidence of the most common birth anomalies. Why does the pie chart NOT include behavioral disorders such as autism spectrum disorder?

Accepted Answer

Behavioral disorders such as autism spectrum disorder are not detected at birth, and therefore their incidence cannot be accurately represented in a pie chart of birth anomalies.

Question 8

In a study of concordance, a sample of identical twins was evaluated for adult-onset diabetes. The data below were collected for this trait:
1. In 36 identical twin pairs, both showed adult-onset diabetes.
2. In 40 identical twin pairs, only one showed adult-onset diabetes.
3. In 336 identical twin pairs, neither showed adult-onset diabetes.
The concordance for adult-onset diabetes among fraternal twins is 10%. Thus, this trait is not likely to have a strong genetic component.

Accepted Answer

The concordance rate among identical twins (36 out of 76 pairs where at least one twin has diabetes) is significantly higher than the 10% concordance rate for fraternal twins, suggesting a strong genetic component. Identical twins share more genetic material than fraternal twins, so a higher concordance rate in identical twins indicates a genetic influence.

Question 9

Personalized medicine refers to the idea of:

Accepted Answer

Personalized medicine primarily focuses on using a patient's genetic information to tailor medical treatment.

Question 10

For which of the following traits do genetic risk factors transmitted from parent to offspring NOT play a major role in the development of the trait?

Accepted Answer

Handedness is not directly influenced by genetic factors. While genetics may play a small role, handedness is largely determined by environmental factors during fetal and early childhood development. Choices A, B, D, and E are all traits that have been shown to have significant genetic components.

Question 11

In a study of concordance, a sample of identical twins was evaluated for adult-onset diabetes. The data below were collected for this trait:
1. In 36 identical twin pairs, both showed adult-onset diabetes.
2. In 40 identical twin pairs, only one s3. In 336 identical twin pairs, neither showed adult-onset diabetes.
Item 3 shows that a majority of identical twins do not have the disease, and gives us the most information with regard to concordance of the trait.howed adult-onset diabetes.

Accepted Answer

The statement about item 3 providing the most information regarding concordance is incorrect. Concordance in identical twins is more informatively assessed by comparing the number of twin pairs where both have the disease to the number where only one does. The data showing both twins with the disease (36 pairs) versus only one twin with the disease (40 pairs) directly addresses concordance, not the number of pairs where neither has the disease (336 pairs).

Question 12

Lindsay and Joy are twins that share the same genetic material and appear so similar that their teachers cannot tell them apart. Lindsay and Joy are _____ twins.

Accepted Answer

Identical twins are also known as monozygotic twins, meaning they originate from a single zygote that splits and forms two individuals with the same genetic material.

Question 13

A small difference between the concordance rates seen in fraternal and identical suggests that:

Accepted Answer

A small difference in concordance rates between fraternal and identical twins suggests that environmental factors play a larger role than genetic factors in the trait being studied, as identical twins share more of their genetics compared to fraternal twins.

Question 14

_____ is defined as the percentage of cases in which both members of a pair of twins show the trait when it is known that at least one member shows it.

Accepted Answer

Concordance refers to the percentage of cases in which both members of a pair of twins show the trait when it is known that at least one member shows it. Therefore, choice A is the correct answer. Discordance refers to the opposite, where only one twin shows the trait. Epistasis refers to the interaction between genes that can affect the expression of a trait. Accordance is not a relevant term in genetics. Monozygocity refers to twins who develop from a single fertilized egg and are genetically identical.

Question 15

BRCA1 and BRCA2 are:

Accepted Answer

BRCA1 and BRCA2 are genes that produce proteins involved in the repair of damaged DNA, playing a critical role in maintaining the stability of a cell's genetic information.

Question 16

A concordance of 50% for a trait occurring in identical twins only provides evidence for the role of nature or genes in the development of this trait, and does not yield any information regarding the role of nurture or environment in this trait.

Accepted Answer

A concordance of 50% in identical twins suggests that both genetics (nature) and environment (nurture) play roles in the development of the trait, as identical twins share the same genes but the trait does not occur in both twins 100% of the time, indicating environmental influences.

Question 17

In a study of concordance, a sample of identical twins was evaluated for adult-onset diabetes. The data below were collected for this trait:
1. In 36 identical twin pairs, both showed adult-onset diabetes.
2. In 40 identical twin pairs, only one showed adult-onset diabetes.
3. In 336 identical twin pairs, neither showed adult-onset diabetes.
The data above imply that the environment is not an important component of adult-onset diabetes.

Accepted Answer

The presence of identical twin pairs where only one twin developed adult-onset diabetes (40 pairs) suggests that factors other than genetics, such as environmental factors, play a role in the development of the condition.

Question 18

In a study of concordance, a sample of identical twins was evaluated for adult-onset diabetes. The data below were collected for this trait:
1. In 36 identical twin pairs, both showed adult-onset diabetes.
2. In 40 identical twin pairs, only one showed adult-onset diabetes.
3. In 336 identical twin pairs, neither showed adult-onset diabetes.
Items 1 and 2 can be used to calculate concordance for identical twins as follows: 36/(36 + 40) × 100 = 47%.

Accepted Answer

The concordance rate is calculated by dividing the number of twin pairs where both twins exhibit the trait (in this case, adult-onset diabetes) by the total number of twin pairs where at least one twin exhibits the trait, then multiplying by 100 to get a percentage. Here, 36 pairs both have diabetes out of 76 pairs where at least one has it (36 with both + 40 with one), resulting in a concordance rate of 47%.

Question 19

Some tentative patterns that are emerging from the study of complex traits are that:

Accepted Answer

The answer of Some tentative patterns that are emerging from...

Question 20

Only by studying identical twins raised in separate environments can scientists uncover the role of genes vs. environment in the development of a specific trait. Comparing the occurrence of the trait in identical vs. fraternal twins yields little usable data.

Accepted Answer

Comparing identical and fraternal twins, even when raised in the same environment, is a valuable method because it helps to distinguish the effects of genetics from the environment. Identical twins share more genetic material than fraternal twins, so differences in the occurrence of traits between these groups can provide insights into the role of genetics versus environment.

Quiz 18: The Genetic and Environmental Basis of Complex Traits