-
Question 1
Correct
-
A 66 year old man visits the clinic because he has been experiencing increasing breathlessness for the past five months while doing daily tasks. His exercise tolerance is now limited to 75 metres while on a flat surface and walking up the stairs makes him breathless. He sleeps on four pillows and has swollen ankles in the morning. He occasionally coughs up phlegm. Past Medical history of importance: 36 pack year smoking history Hypertension Ischaemic heart disease Coronary artery stenting done 10 months ago Pulmonary function testing revealed: FEV1 0.90 L (1.80 – 3.02 predicted) FVC 1.87 L (2.16 – 3.58 predicted) Diffusion capacity 3.0 mmol/min/kPa (5.91 – 9.65 predicted) Total lung capacity 4.50 L (4.25 – 6.22 predicted) Residual volume 2.70 L (1.46 – 2.48 predicted) Which condition does he have?
Your Answer: Chronic obstructive pulmonary disease
Explanation:Whilst asthma and COPD are different diseases they cause similar symptoms, which can present a challenge in identifying which of the two diseases a patient is suffering from. COPD causes chronic symptoms and narrowed airways which do not respond to treatment to open them up. In the case of asthma the constriction of the airways through inflammation tends to come and go and treatment to reduce inflammation and to open up the airways usually works well.
COPD is more likely than asthma to cause a chronic cough with phlegm and is rare before the age of 35 whilst asthma is common in under-35s. Disturbed sleep caused by breathlessness and wheeze is more likely in cases of asthma, as is a history of allergies, eczema and hay fever. Differentiating between COPD and asthma requires a history of both symptoms and spirometry. The spirometry history should include post bronchodilator measurements, the degree of reversibility and, ideally, home monitoring which gives a history of diurnal variation.
Airflow Obstruction: Both asthma and COPD are characterised by airflow obstruction. Airflow obstruction is defined as a reduced FEV1 and a reduced FEV1/FVC ratio, such that FEV1 is less than 80% of that predicted, and FEV1/FVC is less than 0.7.
These episodes are usually associated with widespread, but variable, airflow obstruction within the lung that is often reversible either spontaneously or with treatment.
COPD: COPD is a chronic, slowly progressive disorder characterised by airflow obstruction (reduced FEV1 and FEV1/VC ratio) that does not change markedly over several months. The airflow obstruction is not fully reversible.
Spirometry COPD Asthma
VC Reduced Nearly normal
FEV1 Reduced Reduced in attack
FVC (or FEV6) Reduced Nearly normal
FEV1 Ratio
(of VC/FVC/FEV6) Reduced in attackThis man has a low FEV1 and FVC. His diffusions capacity is also low despite having a normal total lung capacity. These values confirm a diagnosis of COPD.
-
This question is part of the following fields:
- Respiratory
-
-
Question 2
Incorrect
-
A 32 year old male with a history of smoking half a pack of cigarettes per day complains of worsening breathlessness on exertion. He was working as a salesman until a few months ago. His father passed away due to severe respiratory disease at a relatively young age. Routine blood examination reveals mild jaundice with bilirubin level of 90 µmol/l. AST and ALT are also raised. Chest X-ray reveals basal emphysema. Which of the following explanation is most likely the cause of these symptoms?
Your Answer: COPD secondary to excessive smoking
Correct Answer: α-1-Antitrypsin deficiency
Explanation:Alpha-1 antitrypsin deficiency is an inherited disorder that may cause lung and liver disease. The signs and symptoms of the condition and the age at which they appear vary among individuals. This would be the most likely option as it is the only disease that can affect both liver and lung functions.
People with alpha-1 antitrypsin deficiency usually develop the first signs and symptoms of lung disease between ages 20 and 50. The earliest symptoms are shortness of breath following mild activity, reduced ability to exercise, and wheezing. Other signs and symptoms can include unintentional weight loss, recurring respiratory infections, fatigue, and rapid heartbeat upon standing. Affected individuals often develop emphysema. Characteristic features of emphysema include difficulty breathing, a hacking cough, and a barrel-shaped chest. Smoking or exposure to tobacco smoke accelerates the appearance of emphysema symptoms and damage to the lungs.
About 10 percent of infants with alpha-1 antitrypsin deficiency develop liver disease, which often causes yellowing of the skin and sclera (jaundice). Approximately 15 percent of adults with alpha-1 antitrypsin deficiency develop liver damage (cirrhosis) due to the formation of scar tissue in the liver. Signs of cirrhosis include a swollen abdomen, swollen feet or legs, and jaundice. Individuals with alpha-1 antitrypsin deficiency are also at risk of developing hepatocellular carcinoma. -
This question is part of the following fields:
- Respiratory
-
-
Question 3
Incorrect
-
A 20 year old heroin addict is admitted following an overdose. She is drowsy and has a respiratory rate of 6 bpm. Which of the following arterial blood gas results (taken on room air) are most consistent with this?
Your Answer: pH = 7.55; pCO2 = 3.4 kPa; pO2 = 14.3 kPa
Correct Answer: pH = 7.31; pCO2 = 7.4 kPa; pO2 = 8.1 kPa
Explanation:In mild-to-moderate heroin overdoses, arterial blood gas (ABG) analysis reveals respiratory acidosis. In more severe overdoses, tissue hypoxia is common, leading to mixed respiratory and metabolic acidosis.
The normal range for PaCO2 is 35-45 mmHg (4.67 to 5.99 kPa). Respiratory acidosis can be acute or chronic. In acute respiratory acidosis, the PaCO2 is elevated above the upper limit of the reference range (i.e., >45 mm Hg) with an accompanying academia (i.e., pH < 7.35). In chronic respiratory acidosis, the PaCO2 is elevated above the upper limit of the reference range, with a normal or near-normal pH secondary to renal compensation and an elevated serum bicarbonate levels (i.e., >30 mEq/L).
Arterial blood gases with pH = 7.31; pCO2 = 7.4 kPa; pO2 = 8.1 kPa would indicate respiratory acidosis.
-
This question is part of the following fields:
- Respiratory
-
-
Question 4
Incorrect
-
A 14 year old girl with cystic fibrosis (CF) presents with abdominal pain. Which of the following is the pain most likely linked to?
Your Answer: Pyelonephritis
Correct Answer: Meconium ileus equivalent syndrome
Explanation:Meconium ileus equivalent (MIE) can be defined as a clinical manifestation in cystic fibrosis (CF) patients caused by acute intestinal obstruction by putty-like faecal material in the cecum or terminal ileum. A broader definition includes a more chronic condition in CF patients with abdominal pain and a coecal mass which may eventually pass spontaneously. The condition occurs only in CF patients with exocrine pancreatic insufficiency (EPI). It has not been seen in other CF patients nor in non-CF patients with EPI. The frequency of these symptoms has been reported as 2.4%-25%.
The treatment should primarily be non-operative. Specific treatment with N-acetylcysteine, administrated orally and/or as an enema is recommended. Enemas with the water soluble contrast medium, meglucamine diatrizoate (Gastrografin), provide an alternative form for treatment and can also serve diagnostic purposes. It is important that the physician is familiar with this disease entity and the appropriate treatment with the above mentioned drugs. Non-operative treatment is often effective, and dangerous complications following surgery can thus be avoided.
-
This question is part of the following fields:
- Respiratory
-
-
Question 5
Incorrect
-
A 39 year old man was admitted with an exacerbation of asthma. He responded to treatment but the medical intern was concerned that Aspergillus fumigatus was cultured from his sputum. Subsequently arranged serum total, IgE level was elevated at 437 ng/ml (normal 40-180 ng/ml), RAST to Aspergillus fumigatus was class III, Aspergillus fumigatus precipitins were negative. What would be the most appropriate management step in this patient?
Your Answer: Itraconazole
Correct Answer: No change in medication
Explanation:Allergic bronchopulmonary aspergillosis (ABPA) is a form of lung disease that occurs in some people who are allergic to Aspergillus. With ABPA, this allergic reaction causes the immune system to overreact to Aspergillus leading to lung inflammation. ABPA causes bronchospasm (tightening of airway muscles) and mucus build-up resulting in coughing, breathing difficulty and airway obstruction.
Blood tests are used to look for signs of an allergic reaction. This includes evaluating your immunoglobulin E (IgE) level. This level is increased with any type of allergy. Many people with asthma have higher than normal IgE levels. In ABPA however, the IgE level is extremely high (more than 1000 ng/ml or 417 IU/ml). In addition to total IgE, all patients with ABPA have high levels of IgE that is specific to Aspergillus. A blood test can be done to measure specific IgE to Aspergillus. A blood or skin test for IgE antibodies to Aspergillus can be done to see if a person is sensitized (allergic) to this fungus. If these skin tests are negative (i.e. does not show a skin reaction) to Aspergillus fumigatus, the person usually does not have ABPA.
Therefore, there should be no change in medication since this patient does not have ABPA. -
This question is part of the following fields:
- Respiratory
-
-
Question 6
Correct
-
A 27-year-old man with a history of asthma presents for review. He has recently been discharged from hospital following an acute exacerbation and reports generally poor control with a persistent night time cough and exertional wheeze. His current asthma therapy is: salbutamol inhaler 100mcg prn Clenil (beclomethasone dipropionate) inhaler 800mcg bd salmeterol 50mcg bd He has a history of missing appointments and requests a prescription with as few side-effects as possible. What is the most appropriate next step in management?
Your Answer: Leukotriene receptor antagonist
Explanation:The NICE 2019 guidelines states that in patients who are uncontrolled with a SABA (Salbutamol) and ICS (Beclomethasone), LTRA should be added.
If asthma is uncontrolled in adults (aged 17 and over) on a low dose of ICS as maintenance therapy, offer a leukotriene receptor antagonist (LTRA) in addition to the ICS and review the response to treatment in 4 to 8 weeks. -
This question is part of the following fields:
- Respiratory
-
-
Question 7
Correct
-
Which of the following measurements is a poor prognostic factor in patients suffering from pneumonia?
Your Answer: Respiratory rate 35/min
Explanation:CURB Pneumonia Severity Score estimates the mortality of community-acquired pneumonia to help determine inpatient vs. outpatient treatment.
Select Criteria:
Confusion (abbreviated Mental Test Score <=8) (1 point)
Urea (BUN > 19 mg/dL or 7 mmol/L) (1 point)
Respiratory Rate > 30 per minute (1 point)
Blood Pressure: diastolic < 60 or systolic < 90 mmHg (1 point) The CURB-65 scores range from 0 to 5. Clinical management decisions can be made based on the score:
Score Risk Disposition
0 or 1 – 1.5% mortality – Outpatient care
2 – 9.2% mortality – Inpatient vs. observation admission
≥ 3 – 22% mortality – Inpatient admission with consideration for ICU admission with score of 4 or 5 -
This question is part of the following fields:
- Respiratory
-
-
Question 8
Incorrect
-
A 54 year old male, with a smoking history of 15 pack years presents with worsening dyspnoea, fever and cough. He works at a foundry. Vitals are as follows: Respiratory rate: 28/min Heart rate: 80 bpm Temp: 37.6C Chest auscultation reveals bilateral crepitations throughout the lung fields. Calcified hilar nodules are visible on the chest X-ray. Further evaluation shows an eggshell calcification on HRCT. Which of the following is the most likely diagnosis?
Your Answer: Sarcoidosis
Correct Answer: Silicosis
Explanation:Silicosis is a common occupational lung disease that is caused by the inhalation of crystalline silica dust. Silica is the most abundant mineral on earth. Workers that are involved for example in construction, mining, or glass production are among the individuals with the highest risk of developing the condition. Acute silicosis causes severe symptoms (e.g., exertional dyspnoea, cough with sputum) and has a very poor prognosis.
Chronic silicosis has a very variable prognosis and affected individuals may remain asymptomatic for several decades. However, radiographic signs are usually seen early on. Typical radiographic findings are calcifications of perihilar lymph nodes, diffuse ground glass opacities, large numbers of rounded, solitary nodules or bigger, confluent opacities. Avoiding further exposure to silica is crucial, especially since the only treatment available is symptomatic (e.g., bronchodilators). Silicosis is associated with an increased risk of tuberculosis and lung cancer. Berylliosis typically affects individuals who are exposed to aerospace industry. Histoplasmosis and tuberculosis do not form eggshell calcifications. -
This question is part of the following fields:
- Respiratory
-
-
Question 9
Correct
-
A 73 year old woman attends COPD clinic for review. Her blood gases were checked on her last visit two months back. The test was repeated again today. The paO2 on both occasions was 6.8 kPa. There is no CO2 retention on 28% O2. She stopped smoking around 6 months ago and is maintained on combination inhaled steroids and long acting b2-agonist therapy. What is the next best step in management?
Your Answer: Suggest she uses an oxygen concentrator for at least 19 h per day
Explanation:Long-term oxygen therapy (LTOT) ≥ 15 h/day improves survival in hypoxemic chronic obstructive pulmonary disease (COPD). It significantly helps in reducing pulmonary hypertension associated with COPD and treating underlying pathology of future heart failure. There is little to no benefit of oxygen therapy for less than 15 hours.
-
This question is part of the following fields:
- Respiratory
-
-
Question 10
Incorrect
-
A 35 year old male who has smoked 20 cigarettes per day was referred to the National Chest Hospital because he has had a nine month history of shortness of breath which is getting worse. Tests revealed that he had moderate emphysema. His family history showed that his father died from COPD at the age of 52. Genetic testing found the PiSZ genotype following the diagnosis of alpha-1 antitrypsin (A1AT) deficiency. What levels of alpha-1 antitrypsin would be expected if they were to be measured?
Your Answer: 10% of normal
Correct Answer: 40% of normal
Explanation:Alpha1-antitrypsin (AAT) deficiency, first described in 1963, is one of the most common inherited disorders amongst white Caucasians. Its primary manifestation is early-onset of pan acinar emphysema. In adults, alpha1-antitrypsin deficiency leads to chronic liver disease in the fifth decade. As a cause of emphysema, it is seen in non-smokers in the fifth decade of life and during the fourth decade of life in smokers.
Symptoms of alpha1-antitrypsin (AAT) deficiency emphysema are limited to the respiratory system. Dyspnoea is the symptom that eventually dominates alpha1-antitrypsin deficiency. Similar to other forms of emphysema, the dyspnoea of alpha1-antitrypsin deficiency is initially evident only with strenuous exertion. Over several years, it eventually limits even mild activities.
The serum levels of some of the common genotypes are:
•PiMM: 100% (normal)
•PiMS: 80% of normal serum level of A1AT
•PiSS: 60% of normal serum level of A1AT
•PiMZ: 60% of normal serum level of A1AT, mild deficiency
•PiSZ: 40% of normal serum level of A1AT, moderate deficiency
•PiZZ: 10–15% (severe alpha 1-antitrypsin deficiency) -
This question is part of the following fields:
- Respiratory
-
-
Question 11
Incorrect
-
A 73 year old woman presents with severe emphysema. She is on maximal therapy including high dose Seretide and tiotropium. She tells you that she is so unwell that she can barely manage the walk the 160 metres to the bus stop. On examination she looks short of breath at rest. Her BP is 158/74 mmHg, pulse is 76 and regular. There are quiet breath sounds, occasional coarse crackles and wheeze on auscultation of the chest. Investigations show: Haemoglobin 14.2 g/dl (13.5-17.7) White cell count 8.4 x 109/l (4-11) Platelets 300 x 109/l (150-400) Sodium 137 mmol/l (135-146) Potassium 4.1 mmol/l (3.5-5) Creatinine 127 micromole/l (79-118) pH 7.4 (7.35-7.45) pCO2 7.5 kPa (4.8-6.1) pO2 9.7 kPa (10-13.3) Chest x-ray – Predominant upper lobe emphysema. FEV1 – 30% of predicted. Which of the features of her history, examination or investigations would preclude referral for lung reduction surgery?
Your Answer: Predominant upper lobe emphysema
Correct Answer: pCO2 7.4
Explanation:Nice guidelines for lung reduction surgery:
FEV1 > 20% predicted
PaCO2 < 7.3 kPa
TLco > 20% predicted
Upper lobe predominant emphysemaThis patient has pCO2 of 7.4 so she is unsuitable for referral for lung reduction surgery.
-
This question is part of the following fields:
- Respiratory
-
-
Question 12
Correct
-
A 56 year old man who is a known alcoholic presents to the clinic with a fever and cough. Past medical history states that he has a long history of smoking and is found to have a cavitating lesion on his chest x-ray. Which organism is least likely to be the cause of his pneumonia?
Your Answer: Enterococcus faecalis
Explanation:Cavitating pneumonia is a complication that can occur with a severe necrotizing pneumonia and in some publications it is used synonymously with the latter term. It is a rare complication in both children and adults. Albeit rare, cavitation is most commonly caused by Streptococcus pneumoniae, and less frequently Aspergillus spp., Legionella spp. and Staphylococcus aureus.
In children, cavitation is associated with severe illness, although cases usually resolve without surgical intervention, and long-term follow-up radiography shows clear lungs without pulmonary sequelae
Although the absolute cavitary rate may not be known, according to one series, necrotizing changes were seen in up to 6.6% of adults with pneumococcal pneumonia. Klebsiella pneumoniae is another organism that is known to cause cavitation.Causative agents:
Mycobacterium tuberculosis
Klebsiella pneumoniae
Streptococcus pneumoniae
Staphylococcus aureusEnterococcus faecalis was not found to be a causative agent.
-
This question is part of the following fields:
- Respiratory
-
-
Question 13
Correct
-
A patient with a history of asthma presents with worsening of her symptoms and dyspnoea. She recently started taking a new medicine and she feels it might have aggravated her symptoms. Which of the following is likely responsible for her symptoms?
Your Answer: Timolol eye drops
Explanation:β-blockers are the class of drug most often chosen to treat glaucoma, although other medical therapies are available. Systemic absorption of timolol eye drops can cause unsuspected respiratory impairment and exacerbation of asthma. Physicians should be alert to the possibility of respiratory side-effects of topical therapy with β-blockers. Leukotriene antagonists and salbutamol are used in asthma treatment. HRT and ferrous sulphate do not lead to the exacerbation of asthma.
-
This question is part of the following fields:
- Respiratory
-
-
Question 14
Incorrect
-
A 23 year old female is admitted with acute severe asthma. Treatment is initiated with 100% oxygen, nebulised salbutamol and ipratropium bromide nebulisers and IV hydrocortisone. There is no improvement despite initial treatment. What is the next step in management?
Your Answer: Non-invasive ventilation
Correct Answer: IV magnesium sulphate
Explanation:A single dose of intravenous magnesium sulphate is safe and may improve lung function and reduce intubation rates in patients with acute severe asthma. Intravenous magnesium sulphate may also reduce hospital admissions in adults with acute asthma who have had little or no response to standard treatment.
Consider giving a single dose of intravenous magnesium sulphate to patients with acute severe asthma (PEF <50% best or predicted) who have not had a good initial response to inhaled bronchodilator therapy. Magnesium sulphate (1.2–2 g IV infusion over 20 minutes) should only be used following consultation with senior medical staff.
-
This question is part of the following fields:
- Respiratory
-
-
Question 15
Correct
-
Which of the statements is most accurate regarding the lung?
Your Answer: The medial basal segment is absent in the left lower lobe
Explanation:The right and left lung anatomy are similar but asymmetrical. The right lung consists of three lobes: right upper lobe (RUL), right middle lobe (RML), and right lower lobe (RLL). The left lung consists of two lobes: right upper lobe (RUL) and right lower lobe (RLL). The right lobe is divided by an oblique and horizontal fissure, where the horizontal fissure divides the upper and middle lobe, and the oblique fissure divides the middle and lower lobes. In the left lobe there is only an oblique fissure that separates the upper and lower lobe.
The lobes further divide into segments which are associated with specific segmental bronchi. Segmental bronchi are the third-order branches off the second-order branches (lobar bronchi) that come off the main bronchus.
The right lung consists of ten segments. There are three segments in the RUL (apical, anterior and posterior), two in the RML (medial and lateral), and five in the RLL (superior, medial, anterior, lateral, and posterior). The oblique fissure separates the RUL from the RML, and the horizontal fissure separates the RLL from the RML and RUL.
There are eight to nine segments on the left depending on the division of the lobe. In general, there are four segments in the left upper lobe (anterior, apicoposterior, inferior and superior lingula) and four or five in the left lower lobe (lateral, anteromedial, superior and posterior). The medium sized airways offer the maximum airway resistance, not smaller ones.
-
This question is part of the following fields:
- Respiratory
-
-
Question 16
Incorrect
-
A 66-year-old man with newly-diagnosed small cell carcinoma discusses his further treatment options with the team of doctors. Which statement is incorrect about small cell carcinoma?
Your Answer: Radiotherapy has no role to play in the treatment of small cell lung cancer
Correct Answer: Patients with small cell lung cancer always benefit from surgery
Explanation:Small cell lung cancer (SCLC) is characterized by rapid growth and early dissemination. Prompt initiation of treatment is important.
Patients with clinical stage Ia (T1N0) after standard staging evaluation may be considered for surgical resection, but combined treatment with chemotherapy and radiation therapy is the standard of care. Radiation therapy is often added at the second cycle of chemotherapy.
Historically, patients undergoing surgery for small cell lung cancer (SCLC) had a dismal prognosis. However, more recent data suggest that patients with true stage I SCLC may benefit from surgical resection.
Common sites of hematogenous metastases include the brain, bones, liver, adrenal glands, and bone marrow. The symptoms depend upon the site of spread.
-
This question is part of the following fields:
- Respiratory
-
-
Question 17
Incorrect
-
A 68 year old man who has chronic obstructive pulmonary disease (COPD) is reviewed. On examination, there is evidence of cor pulmonale with a significant degree of pedal oedema. His FEV1 is 44%. During a recent hospital stay his pO2 on room air was 7.4 kPa. Which one of the following interventions is most likely to increase survival in this patient?
Your Answer: Inhaled corticosteroid
Correct Answer: Long-term oxygen therapy
Explanation:Assess the need for oxygen therapy in people with:
– very severe airflow obstruction (FEV1 below 30% predicted)
– cyanosis (blue tint to skin)
– polycythaemia
– peripheral oedema (swelling)
– a raised jugular venous pressure
– oxygen saturations of 92% or less breathing air.Also consider assessment for people with severe airflow obstruction (FEV1 30–49% predicted).
Consider long-term oxygen therapy for people with COPD who do not smoke and who:
have a partial pressure of oxygen in arterial blood (PaO2) below 7.3 kPa when stable or have a PaO2 above 7.3 and below 8 kPa when stable, if they also have 1 or more of the following:
– secondary polycythaemia
– peripheral oedema
– pulmonary hypertension. -
This question is part of the following fields:
- Respiratory
-
-
Question 18
Correct
-
From the options provided below, which intervention plays the greatest role in increasing survival in patients with COPD?
Your Answer: Smoking cessation
Explanation:Smoking cessation is the most effective intervention in stopping the progression of COPD, as well as increasing survival and reducing morbidity. This is why smoking cessation should be the top priority in the treatment of COPD. Long term oxygen therapy (LTOT) may increase survival in hypoxic patients. The rest of the options dilate airways, reduce inflammation and thereby improve symptoms but do not necessarily increase survival.
-
This question is part of the following fields:
- Respiratory
-
-
Question 19
Correct
-
A phrenic nerve palsy is caused by which of the following?
Your Answer: Aortic aneurysm
Explanation:Phrenic nerve palsy causing hemidiaphragm paralysis is a very uncommon feature of thoracic aortic aneurysm.
Thoracic aortic aneurysms are usually asymptomatic however chest pain is most commonly reported symptom. Left hemidiaphragm paralysis, because of left phrenic nerve palsy, is a very rare presentation of thoracic aortic aneurysm.
Thoracic aortic aneurysm may present atypical symptoms such as dysphagia due to compression of the oesophagus; hoarseness due to vocal cord paralysis or compression of the recurrent laryngeal nerve; superior vena cava syndrome due to compression of the superior vena cava; cough, dyspnoea or both due to tracheal compression; haemoptysis due to rupture of the aneurysm into a bronchus; and shock due to rupture of the aneurysm.
Common causes of phrenic nerve palsy include malignancy such as bronchogenic carcinoma, as well as mediastinal and neck tumours. Phrenic nerve palsy can also occur due to a penetrating injury or due to iatrogenic causes arising, for example, during cardiac surgery and central venous catheterization. Many cases or phrenic nerve palsy are idiopathic. -
This question is part of the following fields:
- Respiratory
-
-
Question 20
Incorrect
-
A husband visits the clinic with his wife because he wants to be screened for cystic fibrosis. His brother and wife had a child with cystic fibrosis so he is concerned. His wife is currently 10 weeks pregnant. When screened, he was found to be a carrier of the DF508 mutation for cystic fibrosis but despite this result, the wife declines testing. What are the chances that she will have a child with cystic fibrosis, given that the gene frequency for this mutation in the general population is 1/20?
Your Answer: 1/160
Correct Answer: 1/80
Explanation:The chance of two carriers of a recessive gene having a child that is homozygous for that disease (that is both genes are transmitted to the child) is 25%. Therefore, the chances of this couple having a child with CF are 25%(1/4) x 1/20 = 1/80.
-
This question is part of the following fields:
- Respiratory
-
00
Correct
00
Incorrect
00
:
00
:
0
00
Session Time
00
:
00
Average Question Time (
Secs)