1.
In a study of study-behavior, Dr. Singh estimates a heritability of 90% using only monozygotic twin data. Dr. VVolmar however, estimates a heritability of only 50% using data from adopted siblings. Dr. WoIman also claims that Dr. Singh overestimated the heritability because he did not account for:
Correct Answer
B. Shared environment
Explanation
Dr. WoIman claims that Dr. Singh overestimated the heritability because he did not account for the shared environment. This suggests that Dr. Singh's study did not consider the influence of environmental factors that are shared by the twins, such as their upbringing, family environment, and socio-economic background. The shared environment can have a significant impact on behavior and traits, and by not accounting for it, Dr. Singh's estimate of heritability may be inflated.
2.
Mr. Jeremy Smith is 6'11" tall and married to Jessica, 6'6"; both are above the 95th percentile with regards to height. They have a son Jeremy Jr., and they just had him at the 1-year check-up with the family physician. The doctor measures the son, and tells them that with 95% certainty, their son will be 5'7" when grown to his full height. This surprises the parents, and they want to know why. What is the most likely answer?
Correct Answer
C. The height of their son reflects "regression to the mean"
Explanation
The most likely answer is that the height of their son reflects "regression to the mean". This means that extreme values, such as being in the 95th percentile for height, are likely to move closer to the average or mean value in future generations. In this case, despite both parents being exceptionally tall, it is expected that their son's height will be closer to the average height. This is a common phenomenon observed in various traits and characteristics, where extreme values tend to be less extreme in subsequent generations.
3.
Which of the following is a quantitative trait?
Correct Answer
D. Hip circumference
Explanation
Hip circumference is a quantitative trait because it can be measured and expressed numerically. Unlike the other options, which are disorders or conditions, hip circumference is a physical characteristic that can be quantified using standard measurement techniques.
4.
In the following pedigree is shown a family with Hirschsprung's disease. Based on your
knowledge of this disease and what you see in the pedigree, you conclude that there is a presence of:
Correct Answer
E. A major gene
Explanation
The presence of a major gene is concluded based on the given pedigree showing a family with Hirschsprung's disease. Hirschsprung's disease is a congenital condition caused by the absence of nerve cells in the colon, leading to severe symptoms such as constipation and intestinal blockage. The presence of a major gene suggests that a single gene mutation is responsible for the disease in this family, rather than multiple genes or complex inheritance patterns. Therefore, the correct answer is a major gene.
5.
In the last century, several countries instituted policies where sterilization was forced or, for example, people with mental retardation. In addition to this being ethically questionable, it was also wrong because:
Correct Answer
A. Most of the cases caused by dominant diseases come from new mutations
Explanation
Forced sterilization policies for individuals with mental retardation or other conditions was ethically questionable and wrong because most of the cases caused by dominant diseases come from new mutations. This means that sterilizing individuals with these conditions would not have prevented the occurrence of such diseases in future generations. It is important to note that most dominant alleles are hidden in heterozygotes, meaning that individuals carrying these alleles may not exhibit the disease phenotype. Additionally, the loss of recessive alleles through forced sterilization is insignificant compared to the number of hidden dominant alleles in the population.
6.
Assuming that the frequency of geniuses is one in ten thousand both in males and females, and assuming that genius is inherited as a typical multifactorial trait, the risk that the child of a genius is also a genius is approximately
Correct Answer
A. 1%
Explanation
Given that the frequency of geniuses is one in ten thousand for both males and females, and assuming that genius is inherited as a typical multifactorial trait, the risk that the child of a genius is also a genius is approximately 1%. This means that there is a 1% chance that a child born to a genius will inherit the genetic factors that contribute to genius.
7.
Some people believe that the socioeconomic status of the family in which a child is raised is a major determinant of the child's intelligence. This theory implies that individual differences in intelligence are mainly caused by
Correct Answer
E. Shared environment
Explanation
This theory suggests that the shared environment, such as the socioeconomic status of the family, plays a significant role in determining a child's intelligence. It implies that the similarities or differences in intelligence among individuals can be attributed to the common experiences and influences they share within their family environment. This could include factors such as the quality of education, access to resources, and parenting styles that contribute to the development of intelligence.
8.
For some personality traits, for example extraversion, it has been observed that identical twins are quite similar no matter whether they were reared together or apart; but ordinary siblings do not resemble each other much more than ordinary strangers, no matter if they were raised together or apart. This observation suggests an important role for
Correct Answer
E. Non-additive gene effects
Explanation
The observation that identical twins, whether raised together or apart, are quite similar in terms of extraversion suggests that non-additive gene effects play an important role in this personality trait. This means that the combination of genes inherited from both parents interacts in a way that influences the expression of extraversion. In contrast, ordinary siblings, whether raised together or apart, do not resemble each other more than strangers, indicating that shared environment or assortative mating (where individuals with similar traits are more likely to mate) do not have a significant impact on extraversion.
9.
Alcoholism is considered a multifactorial trait that is four times more common in males than in females. According to the multifactorial threshold model, who is at greatest risk of alcoholism?
Correct Answer
B. The son of an alcoholic father
Explanation
According to the given information, alcoholism is considered a multifactorial trait that is more common in males. The question asks who is at the greatest risk of alcoholism. Since the question mentions that alcoholism is more common in males, it can be inferred that the son of an alcoholic father, who is male, would be at the greatest risk.
10.
Incest should not be recommended to the general public because the children of incestuous unions have an increased risk of
Correct Answer
D. Multifactorial and autosomal recessive diseases, but not autosomal dominant diseases and chromosome aberrations
Explanation
Incestuous unions can lead to an increased risk of multifactorial and autosomal recessive diseases in the children. This means that the children may be more likely to develop diseases that are influenced by both genetic and environmental factors, as well as diseases that are caused by inheriting two copies of a recessive gene. However, the answer states that the children are not at an increased risk for autosomal dominant diseases, which are caused by inheriting a dominant gene, and chromosome aberrations, which are structural changes in the chromosomes.
11.
Cleft hp occurs with a frequency of about 1 in 900. Since cleft Hp behaves as a typical multifactorial disorder, you can predict that
Correct Answer
A. The recurrence risk after the birth of an affected child is close to 3%
Explanation
The given correct answer states that the recurrence risk after the birth of an affected child is close to 3%. This means that if a couple has a child with cleft Hp, there is a high likelihood (around 3%) that their subsequent children will also be affected by the disorder. This suggests that cleft Hp is a multifactorial disorder, meaning it is influenced by both genetic and environmental factors. The answer implies that the risk of recurrence is not significantly increased above the population incidence, indicating that the risk of having another affected child is similar to the general population frequency of cleft Hp (1 in 900).
12.
Which of the following observations is the strongest evidence for an important genetic component in the causation of type-1. diabetes mellitus (IDDM)?
Correct Answer
E. The concordance rate in monozygotic twins is five times that in dizygotic twins
Explanation
The concordance rate in monozygotic twins being five times that in dizygotic twins suggests a strong genetic component in the causation of type-1 diabetes mellitus (IDDM). This means that if one twin has the disease, there is a higher likelihood that the other twin will also have it if they are monozygotic (identical) twins compared to dizygotic (fraternal) twins. This indicates that genetic factors play a significant role in the development of IDDM.
13.
In a condition such as schizophrenia the recurrence risk will be greatest for which of the following relatives of an affected individual?
Correct Answer
A. Brother
Explanation
In a condition such as schizophrenia, the recurrence risk is generally higher for siblings or brothers of an affected individual. This is because siblings share a higher genetic similarity compared to other relatives mentioned in the options. While other relatives may also have some genetic risk, the risk is generally highest for siblings due to the closer genetic relationship.
14.
The lecture slides on schizophrenia contain the following: "risk factor: age of father". The most likely explanation of this observation is that:
Correct Answer
A. New mutations are important for schizopHrenia risk
Explanation
The lecture slides mention that the age of the father is a risk factor for schizophrenia. This suggests that new mutations, which are more likely to occur in older fathers, play a significant role in increasing the risk of schizophrenia. This explanation aligns with the observation that the age of the father is associated with schizophrenia risk, indicating that new mutations are important in the development of the disorder.