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*Your ConquerHSC Notes are consistently being revised throughout the 2019 HSC Year to ensure quality!

Week 14 Content

Overview of Week 14 Inquiry Question – Do non-infectious diseases cause more deaths than infectious diseases?

Learning Objective #1 – Investigate the causes and effects of non-infectious diseases in humans, including but not limited to:

  • Genetic diseases
  • Diseases caused by environmental exposure
  • Nutritional diseases
  • Cancer

Learning Objective #2 – Collect and represent data to show the incidence, prevalence and mortality rates of non-infectious diseases, for example: 

  • Nutritional diseases
  • Diseases caused by environmental exposure
 

NEW HSC Syllabus Lecture Video – Causes and Effect 

Week 14 Homework Questions

Week 14 Curveball Questions

Week 14 Extension Questions

Solutions to Week 14 Questions

Overview of Week 14 Inquiry Question

Welcome back to Week 14 of your HSC Biology Syllabus Notes!

In this week, we will examine the cause and effect of diseases from in various categories including genetic (inherited), environmental, nutritional as well as due to cancer. 

After that, we will have a look at the incidence, prevalence and mortality rates of a range of diseases and how you should exhibit & interpret them during your HSC exams. 

Learning Objective #1 - Investigate the causes and effects of non-infectious diseases in humans, including but not limited to:

- Genetic Diseases
- Diseases caused by environmental exposure
- Nutritional diseases
- Cancer

Genetic (Inherited) Disease

Tay-Sachs Disease

Cause: An inherited mutation involving the insertion of four base (TATC) in the Hexosaminidase A gene. This results in an modified reading frame of the mRNA by the ribosome. 

Since this mutated gene is recessive, both parents must carry the defective gene, relayed to their gametes which are used to create the offspring.

Effects/Symptoms: Tay-Sachs Disease is somatic mutation resulting in a change in the organism’s physiological characteristics such as rendering the organism unable to produce a protein (an enzyme). This leads in the accumulation of GM2 ganglioside molecule in nerve cells which is not decomposed due to the absence of the enzyme. This results in the death of nerve cells (interneurons) in the brain.

Tay-Sachs Disease is a rare, neurodegenerative disease.

Cystic Fibrosis:

Cause: An inherited mutation involving the deletion of three base (CTT) in the Cystic Fibrosis allele (or gene). This results in one missing amino acid. 

Effects/Symptoms: This gene affect cells that are responsible for the secretion of mucus, sweat and other digestive fluids. As a result of the mutation, there will be production of smelly, thick mucus, sweat and other digestive fluids.  

These thick fluids (e.g. mucus) can block the blood vessels in lung. Therefore the affected individual would have difficulty breathing, performing exercise and they would have the need for constant coughing to clear the airway from mucus for air.

Diseases Caused By Environmental Exposure

Exposure to Electromagnetic Radiation

Skin cancer is a disease resulting from the excessive exposure to ultraviolet radiation present in sunlight. The method through which U.V radiation causes mutation was already discussed in Module 6 by forming thymine dimers which is bonding of thymine bases on the same DNA strand. 

If these dimers are formed and affect in the DNA sequence of the following genes, skin cancer can develop if the dimers are not repaired by repair enzymes in our cells. 

  • Oncogenes
  • Tumor suppressor genes 
  • Stability genes

The cell containing the replicated DNA containing the mutated gene will be passed onto daughter cells, making the daughter cells cancerous (by having the mutated gene).

These cancerous cells can spread into surrounding tissues where it divides and take up nutrients. They may also break up from its original site of formation and enter blood vessel or lymph vessel whereby it gets carried to another site in the body (e.g. ending up in narrow capillaries where it gets stuck and start replicating).

Exposure to Heavy Metal

Furthermore, heavy metal pollution is toxic as they can prevent substrates from binding to enzymes’ active site and thus prevents normal metabolic processes from occurring in living organisms.

Also, most heavy metal bioaccumulates which means that it gets passed along in the food chain can accumulate to lethal quantities. 

The infamous Minamata disaster in 1950s whereby a chemical plant in Japan released chemical waste containing large quantities mercury (a heavy metal) led to a serious disease, called the Minamata disease. The organisms that were exposed to the large quantities of mercury were affected in many ways. Some of these included narrow vision, numbness, slurring of speech and, in severe conditions, it resulted in paralysis, loss of consciousness, convulsions, fever and death. 

As mercury is capable of bioaccumulating like many heavy metals, it means that the mercury is accumulate in the food chain so that consumption of surviving organisms with appreciable amounts of mercury could result in death. Many of the fish that resided in the polluted water had high levels of mercury which were eaten by the unsuspected local population, which resulted in the dangerous health conditions we have mentioned above.

Lead poisoning is an issue as it can be absorbed into the central nervous system, resulting in peripheral neuropathy which is damage to nerves in the PNS. This can also many symptoms such as muscle weakness and numbness.

It is also able to inhibit the synthesis of haemoglobin which results in anaemia disease which yields muscle weakness and tiredness. 

Lead poisoning is an issue when there is flaking lead paint, contaminated soil and workers in informal battery recycling ‘factories’ in developed or third world countries.

Consumption of Excessive Alcohol

Acetaldehyde is a by-product produced by the metabolic pathway of alcohol that is consumed. 

It is toxic and carcinogenic. 

Acetaldehyde has the ability to cause the thickening of the heart muscle, resulting in a disease known as Hypertrophic cardiomyopathy

This could result in heart failure and death. 

The negative effects of alcohol increases with increased concentration or amount consumed.

Consumption of Tobacco

Tobacco contains tar, benzopyrene, nitrosamine and polycyclic aromatic hydrocarbons which is carcinogenic.

This is able they are able to mutate the DNA sequence in oncogenes and tumour suppressor genes, resulting concern.

For instance, as mentioned in Module 6, Benzopyrene is a chemical mutagen and a hydrocarbon present in cigarette smoke that is capable of being inserted between nitrogenous bases, effectively distorting the DNA double helix at the position where benzopyrene is added. This causes wrong nitrogenous bases being complementary paired to template strands during DNA replication. 

  • This effectively alters the mRNA sequence during protein synthesis which may lead to the specification of a different amino acid sequence in the resultant polypeptide chain.
The implications of mutation of oncogenes causing cancer was already explained. 

Nutritional Diseases

Name of Nutritional Disease: Iron deficiency

Cause of Iron Deficiency: 

  • Insufficient intake of iron (e.g. iron-rich food).
  • Conditions, events, disorder or diseases that result in blood loss. During this process, iron dissolved in the blood is loss with the blood exiting the individual.
 

Occurrence of Iron Deficiency:

  • Herbivores (Vegetarians) may intake less iron than carnivore (Meat-Consumers). This is because there much more iron in typical meat meal than in a typical vegetarian meal on average. However, there are vegetables with more iron than meat such as spinach (e.g. 100g of spinach contains more iron than 100g of meat).
  • Women in the child-bearing age also is prone to having iron deficiency due to menstruation. Here, iron in the blood is lost.
  • Individuals from poor areas in the world may not be able to afford as much meat and they may be prone to having iron deficiency. 
 

Symptoms of Iron Deficiency: 

  • Tiredness & Muscle weakness due to less than required oxygen being supplied to cells due to the limited amount of of iron available to manufacture enough haemoglobin due to deficiency.
  • Energy keeps up active and enable us to perform daily activities. 

 

Treatment and/or management of Iron Deficiency:

  • Iron supplements can be taken orally in the form of capsules. 
  • However, underlying causes of the deficiency may also be treated e.g. worm infestation, bleeding bowl, etc. 

Cancer

We have already explored the example of skin cancer in the ‘Diseases caused by Environmental Disease’ mentioned earlier. 

Essentially, it involves mutation of genes that responsible for cancer development:

  • Oncogenes – responsible for specifying proteins used to signal cell growth and development.
  • Tumour suppressor genes – responsible for coding for proteins to stop/control cell growth & development.
  • Stability genes – responsible for coding for proteins in maintaining the rate of mutation of oncogenes and tumour suppressor genes

Learning Objective #2 - Collect and represent data to show the incidence, prevalence and mortality rates of non-infectious diseases, for example:

- Nutritional diseases
- Diseases caused by environmental exposure

Diseases caused by nutritional disease

Iron Deficiency Anaemia (IDA):

In a 2016 study from Hemtaology Clinics of North America, anaemia is affects 27% of the world population.

Up to today, iron deficiency is the cause for approximately 60% of the cases of anaemia (i.e. responsible for 60% for the prevalence rate of iron deficiency anaemia). 

This equates to approximately 2 billion people. 

Other are due to hookworm and schistosomiasis, malaria and hemoglobinpathy.

On a global scale, the highest prevalence rate of iron deficiency anaemia (IDA) is experienced by adult female as well as children below the age of 10. 

In 2015, the morality rate of iron deficiency anaemia is 0.00365% of the world population. 

That being said, Africa and Southeast Asian regions is responsible for carrying 71% of the global mortality rate due to iron deficiency anaemia. Therefore, the global morality rate is not an accurate depiction of the full picture. 

In developing countries, the poor diets that lack iron and limited access to healthcare result in high prevalence and incidence rate of IDA compared to developed countries. Therefore the incidence rate will vary across developing and developed countries and, so, the global incidence rate will not be an accurate representation of the full picture. 

Since symptoms of IDA is difficult to be used to definitively determine that IDA is the cause, it has been estimated that more than half of the affected individuals is not aware that they have IDA. 

More than 50% of the global undernourished population resides in India, due to factors mentioned so far, India has a high incidence rate of iron deficiency anaemia. For populations residing in the urban regions of India, the incidence for IDA is 60% whereas the incidence rate is 69% for rural populations.

 

Vitamin D Deficiency

The prevalence rate of vitamin D deficiency in Australia is 23% during the 2011 Year (i.e. 2011 – 2012). 

Of this, according to the Australia Bureau of Statistics, 17% of the 23% suffered from low levels of deficiency whereas 6% and 1% experienced medium to high levels of deficiency.

It is important to note that this prevalence rate may not be true reflection of the distribution of the deficiency. For instance, from the Australian Bureau of Statistics 2011 – 2012 data, 

  • During winter months, 49% of the people residing in Victoria and ACT were suffering from Vitamin D deficiency during the 2011 Year. This is much higher than the 23% prevalence rate on a national level. 
  • Vice versa, during summer months, 
  • However, Queensland and Northern Territory had prevalence rate that is much lower than 49% during winter months compared to Victoria and ACT.
  • Also, during summer months, the prevalence rate of Vitamin D deficiency was lowered from 49% to 16% and 13% in Victoria and ACT respectively. 

The overall incidence in children ≤ 15 years of age in Australia was 4.9 per 100,000 children of the same age  bracket.

On a national level, the incidence rate of Vitamin D deficiency was 14% in summer and 36% in winter in the 2011 Year (i.e. 2011 – 2012). 

If you are curious and want further reading and information, you can check out: http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/4364.0.55.006Chapter2002011-12

Diseases caused by environmental exposure

Skin Cancer

Australia:

2016 Incidence rate: 51 per 100,000 people

2018 Incidence rate: 50 per 100,000 people 

2016 Mortality rate: 4.5 per 100,000 people

2018 Mortality rate: 6.3 per 100,000 people

America: 

2018 Incidence rate: 12.7 per 100,000 people

2014 Morality Rate: 2.6 per 100,000 people

2015 Morality Rate: 2.4 per 100,000 people

Incidence rate varies depending on location of country – countries located closer to the ozone depletion region will be more exposed to UV Radiation. Also fair-skinned dominant populations will have a higher rate of skin cancer than darker skin dominant populations. 

The prevalence rate of skin cancer is Australia is high as approximately two in three Australians will develop skin cancer by 70.

Heavy Metal Poisoning with equal or more than 25 µg/dL in New Jersey & USA:

The incidence rate for adults affected with lead poisoning in the New Jersey, USA in 2014 are as follows

2014: 1.4 per 100,000 = 0.0014%

To see the full trend from 2000 – 2014, you can visit New Jersey’s Public Health Data Resource Centre at https://www-doh.state.nj.us/doh-shad/indicator/view/Pb_Blood_Adult.Inc25.html

NOTE: There is no fixed concentration value for which lead in the blood is considered poisonous. Some individuals are more tolerant than others. However, it is sure that 40 µg/dL and above, there will be effects experienced for individuals all across the broad. Generally, 5µg/dL or higher is considered above average, especially in children. 

Prevalence Rate: It has been set by the Centre for Disease Control and Prevention that 5µg/dL or higher is considered above average, especially in children. 

The prevalence rate for children with higher than 5µg/dL is 2.5% in the USA.

In developing countries, where the exposure to lead is high due citizens residing close to lead smelting or production plants, there is high prevalence of lead concentration in blood greater than 5µg/dL in children. 

“For instance, 44% of the children population in Jamaica has exceeded this level and reached concentration of 25µg/dL.”

Source for Blood Lead Level: https://en.wikipedia.org/wiki/Blood_lead_level

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