Multifactorial Inheritance Quiz: Test!

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.