Influence of Genes and Environment on Diseases

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Questions and Answers

What is the main difference between incidence rate and prevalence rate of a disease?

Prevalence rate is always lower than incidence rate.

Prevalence rate assesses new cases over a specific time period.

Incidence rate counts new cases while prevalence rate measures existing cases. (correct)

Incidence rate measures the total number of existing cases.

Which factor is most likely to increase the relative risk of developing lung cancer in smokers?

Being of younger age

Having a family history of lung diseases

Low exposure to environmental pollutants

Variances in genes related to tobacco metabolism (correct)

What does multifactorial inheritance imply about traits like height?

Height is solely determined by environmental factors.

Height has a strict genetic determination with no environmental impact.

Height is influenced by multiple genes and environmental factors. (correct)

Height variation can only be attributed to genetic defects.

Why is the prevalence rate of AIDS higher than its incidence rate?

Individuals with AIDS survive for many years. (D) Signup and view all the answers

Which of the following diseases varies in prevalence among different populations?

Cystic fibrosis, common in Europeans but rare in Asians (A) Signup and view all the answers

What is a characteristic of traits subject to multifactorial inheritance?

They show variation based on both genetic and environmental factors. (B) Signup and view all the answers

Which of the following is considered a risk factor for developing diseases?

Age and family history of certain conditions (C) Signup and view all the answers

What can be said about the threshold of liability in certain diseases?

Diseases either present or not may not follow a normal distribution. (A) Signup and view all the answers

What happens to the recurrence risk if more than one family member is affected by a disease?

The family's true risk is better understood. (B) Signup and view all the answers

Which statement correctly reflects the recurrence risk for multifactorial diseases?

Recurrence risk decreases rapidly with more distant relationships. (A) Signup and view all the answers

What distinguishes monozygotic twins from dizygotic twins?

MZ twins are genetically identical, while DZ twins are genetically different. (D) Signup and view all the answers

What does it mean if MZ twins are discordant for a trait?

One twin has the trait while the other does not. (C) Signup and view all the answers

What provides evidence that genes may be involved in the causation of a disease according to adoption studies?

Children born to affected parents develop the disease more often than control populations. (A) Signup and view all the answers

What is a significant characteristic of concordant twins?

They share a trait or characteristic. (B) Signup and view all the answers

How do the concordance rates for schizophrenia in twins generally compare?

Dissimilar, indicating a sizable genetic component. (B) Signup and view all the answers

What is a limitation of twin studies in genetic research?

Environmental assumptions may not be equally valid for all twins. (B) Signup and view all the answers

What percentage of adopted children of schizophrenic parents develops schizophrenia?

8 to 10% (C) Signup and view all the answers

Which of the following disorders has a genetic concordance rate of 30 to 50% in identical twins?

Type 1 diabetes (B) Signup and view all the answers

Which factor increases the risk of coronary heart disease significantly?

Positive family history (D) Signup and view all the answers

How much of the variation in blood pressure can be attributable to genetic factors?

20 to 40% (A) Signup and view all the answers

What is the approximate risk of developing breast cancer if there is an affected first-degree relative?

50 to 80% (D) Signup and view all the answers

Which of the following variables is NOT a risk factor for Type 2 diabetes?

Young age (B) Signup and view all the answers

What is considered a strong familial correlation in obesity studies?

Shared dietary habits (D) Signup and view all the answers

What is the approximate risk of developing schizophrenia if both parents are affected?

50% (D) Signup and view all the answers

What is the genetic contribution to the risk of developing Alzheimer's disease?

60 to 70% (B) Signup and view all the answers

Which enzyme mediates the conversion of ethanol to acetaldehyde?

Alcohol dehydrogenase (B) Signup and view all the answers

What percentage of individuals with a first-degree relative affected by bipolar disorder are at risk of developing the disorder?

5 to 10% (C) Signup and view all the answers

Which of the following statements about type 1 diabetes is correct?

It involves an autoimmune response. (C) Signup and view all the answers

What is the primary risk factor for developing hypertension?

Positive family history (D) Signup and view all the answers

Study Notes

Genes, Environment, Lifestyle, and Common Diseases

The presentation discusses how genes, environment, and lifestyle interact to influence the development of common diseases.
It highlights the importance of considering both genetic and environmental factors.
The module's learning objectives outline the study of how genes influence body structure and function, and how defects in genes lead to genetic diseases.
Chapters 3, 4, 5, and 6 of Guyton and McCance, along with Chapter 5 of McCance, are referenced as relevant reading material for further understanding.

Incidence of Disease in Populations

Incidence rate refers to the number of new cases of a disease during a specific period (typically a year).
Prevalence rate represents the proportion of a population affected by a disease at a particular point in time.
The prevalence rate of a disease can be influenced by the length of survival period of those with the disease.
Certain diseases show variations in prevalence based on the population group
Cystic fibrosis is relatively common in Europeans compared to Asians.
Sickle cell disease is more frequently seen in African Americans than in other populations
Colon cancer is more frequent in the US compared to Japan, while stomach cancer is opposite.
Environmental factors seem to play a significant part in cancer rates in different populations.

Risk Factors

"Relative risk" describes the increased rate of a specific disease amongst exposed individuals.
A huge relative risk increase associated with heavy smoking and the risk of death from lung cancer.
Risk factors for certain diseases can include age, gender, diet, exercise, and family history.
Genes involved in metabolizing substances, like tobacco smoke components, may significantly influence the risk of developing certain diseases (e.g. lung cancer.

Multifactorial Inheritance

Polygenic traits involve the influence of multiple genes on variations in a trait.
Multifactorial traits involve environmental influences interacting with multiple genes to determine the trait.
Height, blood pressure, and many adult diseases (like hypertension and some cancers) are examples of multifactorial traits.
The concept of a 'threshold of liability' describes situations where a disease manifests or does not, based on the combination of genetic and environmental factors.

Recurrence Risk and Transmission Patterns

Estimating the risk of recurrence for multifactorial diseases is often difficult.
The risk of recurrence increases if more family members have the disease, especially if the disease is more severe or affects a different sex.
Risk is also higher if the affected person has close family members with the disease.
Recurrence risk usually decreases as the kinship relation between individuals grows.
The recurrence risk for single-gene diseases decreases by 50% with each degree of relationship.

Twin Studies

Monozygotic (MZ) twins share the same genes and often similar environmental factors; this makes them a good comparison reference.
Dizygotic (DZ) twins share about half of their genes, and their environments can be more different.
Concordance rates for various diseases are compared between MZ and DZ twins to elucidate the influence of genetics.
Twins share similar environments during formative years.
MZ twins are genetically identical, while DZ twins are not.
Data gathered from twin studies frequently suggest that genetic factors contribute to the development of certain characteristics or diseases.

Adoption Studies

Children adopted away from parents with certain diseases can offer insight into the heritability of these diseases.
If the adopted children manifest the same disease more often in comparison to a control group, this provides evidence of a possible genetic component.
Prenatal exposures and environmental influences may affect the adopted children.
Caution is advised in evaluating such studies because possible environmental factors could have influenced the children.

Twins and Adoption Studies Takeaways

Most common diseases aren't solely genetic or environmental in origin.
Both genetic and non-genetic factors interact to determine a person's predisposition to a disease.

Genetics of Common Diseases

Several multifactorial disorders have varied onset times and affect different age groups.
Cardiovascular diseases (heart disease, stroke) are a major cause of mortality in the United States.
Risk factors for these conditions include obesity, smoking, high blood pressure, elevated cholesterol, and a positive family history.
Environmental factors can significantly impact the onset and progression of diseases

Hypertension

Worldwide, hypertension's prevalence reaches 25-30%.
The renin-angiotensin system plays a crucial role in blood pressure regulation.
Environmental factors and genetic predisposition play a key role in the development of this disease.

Cancer

Cancer is a second-most prevalent cause of death in the US.
Tobacco use is responsible for nearly one-third of all cancer cases.
Common cancers like breast cancer are related to family history, and age of onset has correlations to family history of disease.
Genes such as BRCA1 and BRCA2 have strong links with breast and ovarian cancer.
Colorectal and prostate cancers are also influenced by family history.
Heritability for these cancers is approximately 40%

Diabetes

Type 1 diabetes is an autoimmune disorder with genetic and environmental influences.
Genetic predisposition and development of this disease can be seen through fraternal twin studies.
Type 2 diabetes is strongly associated with insulin resistance and is commonly associated with obesity and positive family history, with 70-90% concordance in identical twins.

Obesity

Obesity is defined as BMI greater than 30.
Being overweight affects Americans, about 2/3rds, in addition to the obese.
It's crucial to treat obesity as a risk factor rather than a disease.
Obesity is linked to several other health problems.
Family history and environmental factors—like diet and exercise—play significant roles.

Alzheimer's Disease

Alzheimer's disease is a neurodegenerative disorder leading to dementia.
It frequently emerges in later life, but can have early onset.
Genetic factors and familial links are frequently observed.

Alcoholism

Alcoholism is characterized by heavy alcohol consumption, a chronic disease with genetic and environmental components.
Some alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) genes can affect an individual's metabolism for alcohol.

Psychiatric Disorders

Schizophrenia and bipolar disorder are severe mental illnesses with significant genetic component influence, and a complex interaction of environmental influences.
Strong correlations exist between these disorders and family history.
Risk significantly increases with multiple affected relatives.

Conclusions

Inherited complex diseases frequently have an earlier onset in those with direct familial history. Environmental factors can play significant roles in these developing diseases.
Lifestyle changes such as diet, exercise, and stress reduction have proven beneficial.
Identification of specific genetic factors and mutations related to certain diseases, enabling early detection and prevention, could lead to greater success in prevention.

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Description

This quiz covers how genetics, environment, and lifestyle factors interplay to influence the onset of common diseases. It emphasizes the importance of understanding both hereditary and environmental elements while referencing specific chapters from Guyton and McCance for deeper insights. Additionally, the quiz explores the concepts of incidence and prevalence rates of diseases in populations.