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NURS 500 Patho Ch 5
Patho 500 Genes, Environment and Common Disease
Question | Answer |
---|---|
disease in populations - incidence rate | Number of new cases of a disease reported during a specific period (typically 1 year) divided by the number of individuals in the population |
disease in populations - prevalence rate | Proportion of the population affected by a disease at a specific point in time |
Risk factors - relative risk | Incidence rate of a disease among individuals exposed to a risk factor divided by the incidence rate of a disease among individuals not exposed to a risk factor |
multifactorial inheritance - polygenic | variation in traits caused by the effects of multiple genes |
multifactorial inheritance - multifactorial trait | variation in traits caused by genetic and env/lifestyle factors |
quantitative traits | traits measured on continuous numeric scale |
multifactorial inheritance - threshold model, see slide 6 for image | liability distribution - threshold of liability |
Characteristics of multifactorial disorders - result from hereditary and env factors. Which component is polygenic | Hereditary component is polygenic Individual involved genes follow mendelian principles Many genes act together to influence the expressed trait |
multifactorial inheritance - concordance | expression of the disease in 2 related family members |
multifactorial inheritance - discordance | expression of the disease in one family member, but not a second |
Multifactorial inheritance - twin studies and concordance | Genetic conditions Monozygotic (MZ) twins: 100% concordance Dizygotic (DZ) twins: less than 100% and similar to that among other siblings |
multifactorial inheritance - env conditions | Equal concordance rates among MZ and DZ twins |
multifactorial inheritance - multifactorial conditions | MZ twins with greater concordance than DZ twins, but rates are not 100% |
multifactorial inheritance - adoption studies | gene-env-lifestyle interaction |
Recurrence risks | Recurrence risks of multifactorial diseases can change substantially because gene frequencies as well as environment and lifestyle factors can differ among populations |
recurrence risk becomes higher if more than 1 family member is affected---if expression of disease in proband is more sever, recurrence risk is higher | Recurrence risk is higher if the proband is of the less commonly affected sex Recurrence risk for the disease usually decreases rapidly in remotely related relatives |
nature and nurture considers | genetics = nature----nurture = env/lifestyle |
nature/nurture - concordant trait | both members of a twin share a trait |
nature/nurture - discordant trait | a twin pair does not share a trait |
nature/nurture - adoption studies | Children born to parents who have a disease but are then subsequently adopted by parents lacking the disease are studied for the recurrence of the disease |
genetics of common diseases - congenital malformations | Congenital diseases are present at birth or shortly after birth Most congenital diseases are multifactorial |
adult multifactorial diseases - coronary heart disease | Potential mycocardial infarction caused by atherosclerosis |
CAD risk increases if | There are more affected relatives Affected relatives are female rather than male Age of onset is younger than 55 years |
CAD autosomal dominant familial factors | Autosomal dominant familial hypercholesterolemia, high-fat diet, lack of exercise, smoking, and obesity |
Familial hypercholesterolemia is autosomal dominant with these characteristics | 1 in 500 is heterozygous for FH gene; 1 in 1 million is homozygous for the trait Serum cholesterol 300 to 400 mg/dl in heterozygote; 600 to 1200 mg/dl in homozygote Cholesterol deposits in arteries and skin (xanthomas) |
familial hypercholesterolemia | see slide 18 for image |
HTN is a risk factor for heart dx, stroke & kidney dx---with these characteristics | 20% to 40% of blood pressure variations are genetic; this means that 60% to 80% are environmental Causes of hypertension Sodium intake, lack of exercise, stress, obesity, smoking, and high-fat intake |
Breast cancer affects 12% American women who live to 85 with these fun facts | If a woman has a first-degree relative with breast cancer, her risk doubles Recurrence risk increases if age of onset in the affected relative is early and if the cancer is bilateral |
more breast cancer fun facts | An autosomal dominant form (5%) has been linked to chromosomes 13 and 17 Other genes are implicated |
colorectal cancer will be experienced by 1 in 20 americans and is SECOND only to lung cancer with these risk factors | Genetics High-fat and low-fiber diet are contributors |
diabetes is a leading cause of blindness, heart disease and kidney failure | Two major types Type 1 (insulin-dependent diabetes mellitus) Type 2 (non–insulin-dependent diabetes mellitus) |
Type 1 Diabetes is autoimmune with destruction of Bcells in pancrease bwo Tcell activation and autoantibody production with these genetics | Onset before 40 years of age Higher incidence with offspring of diabetic fathers Recurrence risk 0.55 MZ twin concordance rate 1% to 6% sibling recurrence |
Type 2 Diabetes represents 80-90% of all diabetic cases and has neither HLA nor autoantibodies seen in type 2 --- with these risk factors | Person has insulin resistance or diminished insulin production Risk factors High carbohydrate diet and obesity Recurrence risk 0.90 MZ twin concordance rate 10% to 15% sibling recurrence |
obesity has BMI > 30 with these genetic factors | Adoptive studies Body weights of adopted individuals correlated significantly with their natural parents’ body weights Twin studies Higher concordance in MZ twins than DZ twins |
Alzheimer's risk DOUBLES in individuals who have affected first-degree relative | Mutations in any of three genes that affect amyloid-beta deposition Presenilin 1 (PS1) Presenilin 2 (PS2) Amyloid-beta precursor protein gene (APP) |
Alcoholism - risk is 3-5 TIMES HIGHER in inv with alcoholic parent and these genetic facts | Adoption studies Offspring of nonalcoholic parents, when reared by alcoholic parents, did not have an increased risk Twin studies Concordance rates MZ: >60% DZ: <30% |
schizophrenia genetics | Recurrence risk among the offspring of one affected parent is 10 times higher than the general population Twin and adoption studies indicate that genetic factors are likely to be involved |
bipolar affective disorder | Genetics Minimal environmental influence |