Epidemiology, Biochemistry and Molecular biology II Flashcards
Which of the following is true regarding DNA structures?
(Please select 1 option)
Adenine (A) and guanine (G) are pyrimidine bases IncorrectIncorrect answer selected
Each amino acid is coded by one codon only
Each DNA strand has a pentose-phosphate backbone with projecting bases This is the correct answerThis is the correct answer
Guanine (G) always pairs with thymidine (T), and adenine (A) with cytosine (C)
There are 32 possible codons
Each DNA strand has a pentose-phosphate backbone with projecting bases
Pyrimidine bases are thymidine (T) and cytosine (C).
G always pairs with C and T with A.
Adenine (A) and guanine (G) are purine bases.
There are 64 possible codons, and each amino acid may be coded by more than one codon.
Which of the following techniques is used to identify isolated mRNA directly?
(Please select 1 option)
Denaturing gradient gel electrophoresis
Eastern blotting
Northern blotting
Southern blotting
Western blotting
Northern blotting
Western blotting is used to identify proteins whereas Southern blotting and denaturing gradient gel electrophoresis are used to identify DNA.
Eastern blotting identifies protein post translational modification and is an extension of western blotting.
Hypersensitivity
A Commonly found in blood transfusion reactions
B Deposition of immune complexes
C Hypersensitivity reaction is delayed
D Rapid onset following allergen exposure
Which type of hypersensitivity matches each description?
Type 1
Rapid onset following allergen exposure
Type 1 hypersensitivity is the principal mechanism underlying hay fever, asthma, and anaphylaxis. It is usually initiated by a rapid IgE response to an allergen in atopic individuals resulting from mast cell degranulation.
Hypersensitivity
A Commonly found in blood transfusion reactions
B Deposition of immune complexes
C Hypersensitivity reaction is delayed
D Rapid onset following allergen exposure
Which type of hypersensitivity matches each description?
Type 2
Commonly found in blood transfusion reactions
Type 2 responses result from antibody binding antigen on the cell surface and a resulting complement cascade. This is the mechanism commonly found in autoimmune disease and blood transfusion reactions.
Hypersensitivity
A Commonly found in blood transfusion reactions
B Deposition of immune complexes
C Hypersensitivity reaction is delayed
D Rapid onset following allergen exposure
Which type of hypersensitivity matches each description?
Type 3
Deposition of immune complexes
In type 3 hypersensitivity, immune complexes are formed or deposited, often in the walls of small blood vessels. This activates the complement cascade and recruits inflammatory cells.
Type 3 hypersensitivity is a key feature of autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus (SLE).
Hypersensitivity
A Commonly found in blood transfusion reactions
B Deposition of immune complexes
C Hypersensitivity reaction is delayed
D Rapid onset following allergen exposure
Which type of hypersensitivity matches each description?
Type 4
Hypersensitivity reaction is delayed
Type 4 hypersensitivity is delayed. It is mediated by T-lymphocytes which secrete cytokines and cause macrophage accumulation. These may develop into granuloma, causing progressive damage and fibrosis. Granulomas are features of sarcoidosis and Crohn’s disease.
Which of the following statements regarding mortality rates is correct?
(Please select 1 option)
Crude mortality rates are calculated only from death certificate data
In males over the age of 15 years, age specific death rates increase by 10-20% over each subsequent five year period
Provide little important information about the changing pattern of disease in society
The standardised mortality ratio is the unexpected number of deaths divided by observed number of deaths for a specified group
They are usually standardised for age and sex
They are usually standardised for age and sex This is the correct answerThis is the correct answer
Mortality rates are a very important source of information about the changing pattern of disease in a country.
Most countries have a death certification system, and data from this source can be combined with population census information to calculate a crude mortality rate.
The crude mortality rate = deaths occurring over a one year period divided by the number in the population at midpoint of the year, multiplied by 1,000.
Mortality rates are better expressed as age specific death for males and females and are usually started at 15-19 years, and increased in five year intervals. There is little change in the age specific mortality rate between 15 and 34 years. After 45 years it approximately doubles over each five year period.
The standardised mortality ratio (SMR) is a ratio of expected deaths in an age group (calculated from age specific death rates) divided by the actual number of deaths in a specific group within that age group.
Which of the following is correct regarding immunoglobulin (IgG)?
(Please select 1 option)
Cannot cross the placenta to the fetus
Comprises one antigen-binding site and a site for the binding of complement
Constitutes approximately 25% of all immunoglobulins in a healthy individual
Has a Y-shaped molecular structure
Is secreted from T-lymphocytes
Has a Y-shaped molecular structure
Immunoglobulins (antibodies) are secreted from B-lymphocytes (plasma cells) in response to a specific antigen.
IgGs have a Y-shaped molecular structure. They are composed of two antigen-binding sites and a site for the binding of complement. Both antigen-binding sites are identical and consist of a long and heavy chain.
IgGs constitute approximately 75% of all immunoglobulins in a healthy individual.
Only IgGs can cross the placenta. This is important as they provide immune protection for the newborn in the first few months of life.
Which one of the following statements is correct?
(Please select 1 option)
The arithmetic mean is the measure to be preferred in data which are asymmetrically distributed
The geometric mean is always greater in value than the arithmetic mean
The median is also called the measure of central value
The standard deviation is a poor measure of dispersion
The value of the variable which occurs with the least frequency is the mode
The median is also called the measure of central value
The arithmetic mean is preferred in normal statistics as it generally represents the average.
The geometric mean is the nth root of the product of (a1 … aN) and the arithmetic mean is (a1+ …+aN)/N, hence the geometric mean will always be less than the arithmetic.
The standard deviation (SD) provides a good indication of distribution about the mean.
The mode represents the number occurring with greatest frequency.
Which of the following is true in statistics?
(Please select 1 option)
In a positively skewed distribution, the mean always lies to the left of the mode
In distributions which are markedly skewed, the arithmetic mean is a more appropriate measure than the geometric mean
In parametric data, the mode is usually different in value from the mean
The median is the most commonly occurring value
The standard deviation is also referred to as the root mean square deviation
The standard deviation is also referred to as the root mean square deviation This is the correct answerThis is the correct answer
In positively skewed data the mean usually lies to the right of the mode.
In skewed data, the geometric mean is the most appropriate measure.
Mode refers to the most frequently encountered value and in normally distributed data coincides with the mean and median values.
Standard deviation (SD) is the square root of the mean and is a measure of distribution of the data.
Which of the following is correct in significance testing?
(Please select 1 option)
A type I error is to reject the alternative hypothesis when it should be accepted
A type II error is to accept the alternative hypothesis when it should be rejected
The probability associated with a type I error is the significance level
The significance level is always set to 5%
The significance level is determined at the end of a significance test
The probability associated with a type I error is the significance level
The null hypothesis is that there is no difference between two groups. The alternative hypothesis is that there is a difference.
Rejecting the null hypothesis when there really is no difference between the two groups is a type 1 error.
Accepting the null hypothesis (rejecting the alternative hypothesis) when there is a difference is a type 2 error.
Rejection of the null hypothesis depends on the probability-significance level, which is usually at p
Which one of the following statements concerning statistical tests is true?
(Please select 1 option)
Correlation coefficients vary between -10 and +10
k is the symbol denoting coefficient of correlation
Student’s t-test is a non-parametric test
Wilcoxon’s rank test needs equal sample sizes
y = a + bx is a regression equation
y = a + bx is a regression equation This is the correct answerThis is the correct answer
The variance of correlation coefficients is between −1 and +1.
r is the symbol denoting coefficient of correlation.
Student’s t-test is parametric.
y = a + bx is the equation of a straight line.
Which of the following is true in breast cancer?
(Please select 1 option)
Mutations of the p53 gene are protective
The susceptibility gene BRCA1 confers a risk of over 95% by age 70
The susceptibility gene BRCA2 decreases the risk of male breast cancer
There is a recognised association with ataxia telangiectasia
Up to 50% of new cases have an inherited basis
There is a recognised association with ataxia telangiectasia
Mutations of the p53 gene on chromosome 17p12 are implicated in some inherited and also sporadic forms of breast cancer.
BRCA1 confers a risk of 83% for breast cancer and 63% for ovarian cancer. There is a modest increase in risk for colon and prostate. The BRCA1 gene is on chromosome 17q21.
BCRA2 confers the same risk as BRCA1 for breast cancer in women and is less involved in ovarian cancer. The BRCA2 gene is on chromosome 13q12.
The AT gene on chromosome 11q22 is thought to play an important role in breast cancer, accounting for up to 13% cases in some reports.
In the United Kingdom up to 10% of new cases have an inherited basis which is equivalent to over 1,000 women per year.
A report of a clinical trial of a new post-operative analgesic reads:
“In a comparison between the new drug and a placebo, a higher proportion of patients taking the new drug obtained relief from pain (p
Which of the following statements is correct?
(Please select 1 option)
Amongst 100 patients treated with the drug, five would be expected to have a placebo response
The probable error of the observations is +/- 5%
The result may have occurred by chance alone in less than one in five occasions
The result should be regarded as reaching conventional levels of statistical significance
The trial was well designed
The result should be regarded as reaching conventional levels of statistical significance
It would be false to say that amongst 100 patients treated with the drug five would be expected to have a placebo response. The placebo effect is often higher - of the order or 20-30%.
‘Probable error’ is meaningless; standard error is derived from the variance.
It is true that the result may have occurred by chance alone in less than one in 20 occasions. This is the meaning of the ‘p value’. 0.05 = 1/20.
It is also true that the result should be regarded as reaching conventional levels of statistical significance. p
Regarding statistics, which one of the following is true?
(Please select 1 option)
The incidence tells how common a situation is
The prevalence tells how often a situation occurs
The reliability of a test is defined as the relevance of the test to the activities being treated
The sensitivity of a test is the probability of the test being positive in somebody with the condition
The specificity of a test is the probability of a positive test given the absence of the condition
The sensitivity of a test is the probability of the test being positive in somebody with the condition
The prevalence tells how common a situation is, not the incidence.
The incidence tells how often a situation occurs, not the prevalence.
The relevance of the test to the activities being treated is the validity. Reliability is the ability of a test to produce the same result when repeated under identical conditions.
With regard to statistics which one of the following is true?
(Please select 1 option)
SD = SEM/√n
The SD equals the SEM in non-parametric tests
The SD is a measure of observation variability
The SEM determines the accuracy of measurement of the observations
The standard deviation (SD) is less than the standard error of the mean (SEM)
The SD is a measure of observation variability
SEM = SD/√n
SEM is the standard deviation of all the means of large random samples of size n from a given population. It is of central importance in significance testing.
If testing to see if there is a difference between two population means (for example, t-test) then
t = mean/SEM.
Which of the following is true of achondroplasia?
(Please select 1 option)
Can lead to lumbar lordosis
Individuals have proportionate trunk and limb lengths
Individuals usually have decreased mental development
Is usually a sporadic condition
x Rays shows short dense bones with narrowing of the ends
Can lead to lumbar lordosis
Achondroplasia is usually a hereditary condition but may also occur sporadically.
It particularly affects the pre-bone cartilage of long bones at birth resulting in dwarfism. The affected individuals have a normal trunk length but short stumpy limbs all of the same length. They also have a large head with a saddle nose.
Adult dwarfs have increasing lumbar lordosis, bow legs, and shortened proximal arms and legs.
Intelligence level is usually normal, though there may be delayed motor development and complications of hydrocephalus.
x rays show short dense bones with flared ends with wide epiphysis.
Increased numbers of chromosomes occur in which of the following? (Please select 1 option) Fragile-X syndrome Jacobsen syndrome Klinefelter's syndrome Turner's syndrome Retinoblastoma
Klinefelter’s syndrome
Human cells have 23 pairs of chromosomes, giving a total of 46 per cell.
In Turner’s - XO (that is, X instead of XX or XY) resulting in underdevelopment of female sexual characteristics.
Fragile X syndrome (Martin-Bell syndrome) results from an elongation of the X chromosome causing intellectual, emotional and behavioral features which range from severe to mild in manifestation.
Jacobsen syndrome results from a deletion of the terminal 11q causing mild mental retardation, with poor expressive language skills.
In Klinefelter’s syndrome (XXY) the affected men are usually sterile, and tend to have longer arms and legs and to be taller than their peers.
Retinoblastoma results from a mutation on the RB1 gene on chromosome 13 causing a rapidly developing cancer of the retina.
A random selection of 1200 adults agree to participate in a study of the possible effects of drug X. They are followed prospectively for a period of five years to see if there is an association between the incidence of cataract and the use of drug X. Which type of study is this? (Please select 1 option) Case-control study Cohort study Cross-over study Cross-sectional study Randomised controlled clinical trial
Cohort study
Cohort studies or longitudinal studies involve the follow up of individuals.
A cohort study may be prospective in which individuals who are exposed and non-exposed to a putative risk factor are followed up over a defined period of time and the disease experience of the exposed group at the end of follow up is compared with that of the non-exposed group.
A cohort study may also be historical (retrospective or non-concurrent). A cohort is identified, for whom records of exposure status are available from the past, and whose disease experience can now be measured, a substantial period of time having already elapsed since exposure.
For the data series: 2, 1, 6, 4, 2, which of the following statements is true?
(Please select 1 option)
The mean is 3
The mean is always identical to the median
The median is 3
The mode is 4
The standard deviation is 4
The mean is 3
The mean is the average of the group, the median is the middle of the series with the mode being the most common data point.
The standard deviation is 1.78 (it is definitely not 4 as that would encompass the entire range of the numbers).
The mode is 2 and the median is 2.
Which of the following statements regarding blood groups and blood products is untrue?
(Please select 1 option)
Group O and rhesus negative is the universal donors blood
Stored blood becomes progressively more acidotic and hyperkalaemic with time
Stored blood contains a normal amount of clotting factors
Stored whole blood contains dextrose, phosphate and citrate
The ABO system is inherited in an autosomal dominant pattern
Stored blood contains a normal amount of clotting factors
The universal donors blood is blood group O.
The universal recipient is blood group AB.
Red blood cells (RBCs) are the blood component most frequently used for transfusion. A transfusion of RBCs increases the amount of oxygen that can be carried to the tissues of the body.
RBCs that have been separated from the liquid plasma (packed RBCs) should be administered to patients who have anaemia or who have blood loss. The plasma contains the clotting factors.
Which of the following is correct in statistics?
(Please select 1 option)
A normally distributed population, 95 per cent of the values fall in the range of the mean plus or minus one standard deviation
Standard error and standard deviation (SD) are synonymous
The chi-squared test applies only to parametric data
The statement “p is less than 0.01” means that there is less than 1% likelihood of an event having occurred by chance
Variance is equal to the square-root of the standard deviation
The statement “p is less than 0.01” means that there is less than 1% likelihood of an event having occurred by chance
Mean plus or minus 2 SDs encompasses 95% of normally distributed observations.
Variance is the square of the SD.
SEM=root mean square SD.
Chi-squared test assesses proportions and does not depend upon normality.
Statistical significance is usually accepted at the p
The prevalence rate of a disease has which one of the following features?
(Please select 1 option)
It cannot be estimated from a cross-sectional study
It cannot be used to determine the health needs of a community
It is independent of the duration of illness
It is independent of the incidence of the disease
It measures all the current cases in the community
It measures all the current cases in the community This is the correct answerThis is the correct answer
It is dependent on the number of individuals who contract the disease in a particular time period.
Because it looks at the number of individuals with a disease at a given point in time or within a defined interval, if a patient has recovered from the illness in that duration then they would not be included in the prevalence rate, because it is expressed as a proportion.
As cross-sectional studies are effectively a snap shot they can be used to estimate the proportion of people with a disease at that time and thus the point prevalence.
Prevalence is one measure that can assess the health needs of a community.
In a normal (Gaussian) distribution, which of the following is correct?
(Please select 1 option)
68% of observations lie between the mean 2 standard deviations
95% of observations lie between the mean 2 standard errors
Data from a normal distribution are suitable for non-parametric tests without prior transformation
The 95% confidence interval may be calculated as the mean ±1.96 times the standard error of the mean for population >30
The mean, median and mode do not coincide
The 95% confidence interval may be calculated as the mean ±1.96 times the standard error of the mean for population >30
The mean and median of a normal distribution are equal.
The probability that a normally distributed random variable, x, with mean, σ, and standard deviation, μ, lies between (σ - 1.96μ) and (σ + 1.96σ) is 0.95.
The probability that a normally distributed random variable, x, with mean, σ, and standard deviation, μ, lies between (σ-μ) and (σ+ μ) is 0.68.
Ninety five per cent of the distribution of sample means lies within 1.96 standard deviations of the population mean.
A parametric test is a hypothesis test that makes certain distributional assumptions about the data that they are Gaussian.
