Struggling to make sense of the Module 6 Biology syllabus, wondering what you’ve gotten yourself into? 🤔
Having taught HSC Biology to hundreds of students and classes, and scoring 92% myself in 2020, I’ll be sharing my best tips and notes for mastering these tricky topics in Module 6: Genetic Change.
In this guide, I’m breaking down concepts in a way that makes sense.
You’ll not only be left with a comprehensive set of notes, but you might even begin to find this module pretty exciting (although I admit I may be biased, I liked Biology so much that I made it my degree!)
We’ll be diving into cool things like gene editing and biotechnology – it’s like science fiction coming to life!
So let’s jump in and get ready to ace Module 6 Biology!
General Overview of Module 6 Biology
Topic 1: Mutation
Topic 2: Biotechnology
Topic 3: Genetic Technologies
General Overview of Module 6 Biology: Genetic Change
Genetic Change explores the ways in which new genotypes can be introduced into the population, focusing on a few, complicated concepts.
It goes into detail about the types of mutations and their effects, the environmental pressures that favour certain mutations and lead to species evolution, and the application of biotechnology in agriculture, industry and medicine.
The topics under this module are:
Are you looking for some help with Module 6 Biology? We have an award-winning team of HSC Biology coaches and mentors here to share their expert tips in personalised lessons to help you succeed!
WHEN and HOW will Module 6 Biology be ASSESSED?🧐
Now, typically schools will go through the HSC Biology modules in order, meaning Module 6 falls in Term 1.
Module 6 Biology is usually in the format of a skills-based exam, which will likely fall in about Week 8 of term.
However, schools have the option of making the assessment for Module 6: Genetic Change a depth study, which is often introduced in Weeks 3-4.
So let’s jump in and find out what this module is all about 🙌
For more information on how YOUR school might structure the HSC Biology Modules and Assessments, check out the NESA Sample Assessment Schedules at the bottom of this page!
Topic 1: Mutation
Inquiry question: How does mutation introduce new alleles into a population?
A mutation is any change in the DNA of a cell.
These can negatively or positively affect the organism.
For example, blue eyes only developed when one person experienced a mutation that changed how pigment (melanin) was produced in the iris.
So, humans initially all had brown eyes, which contain more melanin and allow them to see better in brighter environments – it’s like having their own built-in sunglasses!
However, blue-eyed people have greater vision in low-light environments.
You can see how this mutation (having blue eyes) may be viewed as advantageous or disadvantageous depending on the environment of the individual.
But that’s not all…
Mutations might not even affect an organism depending on where it occurs and what type it is!
Mutations can occur in either a non-coding (intron) or coding (exon – remember this as exons are expressed as genes) section of DNA.
If it occurs in a non-coding section, it may alter tRNA or rRNA production.
If it occurs in the coding section, it may change which amino acids are added to the protein, therefore changing the protein that is produced!
Mutagens
But first, we need to identify what is the mutagen?
Mutagens are anything that can cause a change in DNA (a mutation).
We have three classes of mutagens: electromagnetic radiation, chemical and naturally occurring.
| Class of Mutagen | Examples |
|---|---|
| Electromagnetic Radiation | X-rays UV radiation (the sun) Gamma rays (nuclear waste) |
| Chemical | Benzoyl peroxide (acne products) Nitrate preservatives (processed meats) |
| Naturally occuring | Bacteria: Helicobacter pylori can cause stomach ulcers Virus: Human papillomavirus (HPV) can cause cervical cancer |
Genes and Alleles
From my experience tutoring Module 6 Biology, I’ve found these are the two terms that HSC Biology students consistently mix up.
Set yourself apart and understand the distinction- let’s take a look!
A gene refers to a segment of DNA that codes for a specific protein. These can be anywhere between thousands of base pairs long to less than a hundred base pairs.
On the other hand, alleles are variations of a gene. This means alleles are responsible for a lot of the variation we see between individuals.
Here are some examples of genes and their possible alleles:
| Gene | Possible Alleles |
|---|---|
| Eye colour | blue, brown, green |
| Blood Type | A,B, O |
| Hair Type | curly, straight, wavy |
So, thinking back to Module 5 when we were drawing punnett squares, those different letters that we used to demonstrate the inheritance of different traits have a name – They’re alleles!!
If you’re a bit foggy on punnett squares (Module 5) here’s a quick refresher, using a classic punnett square scenario that you could be asked about in the HSC:
Example Question
We have a father who has blue eyes (his phenotype).
Since blue eyes are recessive, (ie. father must have two blue alleles) he would have to be homozygous recessive.
We then have a mother who has brown eyes (her phenotype).
However, since brown is dominant to blue she could be heterozygous (having a blue allele and a brown allele) or homozygous dominant (she only has two brown alleles).
As always we represent the recessive allele (in this case blue) as b and the dominant allele (brown) as B.
So for this punnett square, the gene is eye colour and alleles are brown and blue.
Point Mutations
As always we represent the recessive allele (in this case blue) as b and the dominant allele (brown) as B.
Now that we’ve been introduced to the concept of mutation, let’s apply it to point mutations.
Point mutations refer to mutations that only alter one nucleic base in a gene sequence.
We have three kinds of point mutations that affect an organism to different degrees: substitution, deletion and addition.
Here’s a handy summary table of these mutations before we get into it:
| Mutation | Description of Mutation | Type of Mutation |
|---|---|---|
| Substitution | A nucleotide is swapped out for another | Three possible options:
|
| Deletion | A nucleotide is removed | Frameshift |
| Addition | A nucleotide is added | Frameshift |
Substitution Mutation
There are three possible outcomes of a substitution mutation; silent, missense and nonsense.
1. Silent is the easiest to remember: whilst a nucleotide has changed, the same amino acid is still being produced.
This is because multiple different codons produce the same amino acid. This means the mutation doesn’t change the resulting protein, so it’s ‘silent’. Silent = not noticed.
2. Missense refers to when the substituted nucleotide produces a different amino acid, meaning we are missing the correct amino acid.
3. Nonsense mutations are similar to missense mutations, except that instead of producing a different amino acid, they produce a ‘stop’ codon.
I remember this one as someone telling you to ‘stop talking nonsense’.
Frameshift Mutation
Frameshift mutations are either addition or deletion point mutations.
Deletion and addition mutations are pretty simple – a nucleotide has either been removed (deletion) or added (addition).
These are called frameshift mutations because they don’t just affect one codon or amino acid, but ‘shift the whole reading frame’, causing the remaining protein to be made incorrectly.
I like to think of codons as frames in old movies (the 2011 movie Hugo was one of my favourite movies growing up if you couldn’t tell).
If one of those frames are missing from a film reel, the rest of the movie won’t make sense because it will be out of sync.
You can think of it the same way with frameshift mutations, because it shifts the entire reading frame!
Another important point is making sure to know an example for each type of mutation, and Band 6 responses always link this to its effect.
| Mutation | Example | Effect |
|---|---|---|
| Substitution | Cystic Fibrosis (G551D mutation)
| Leads to thick mucus production and respiratory issues. |
| Deletion | Duchenne Muscular Dystrophy (DMD)
| Muscle degeneration and weakness |
| Addition | Tay-Sachs Disease
| Progressive neurodegeneration, mental delay, early death |
Chromosomal Mutations
If point mutations are small changes in DNA what about BIGGER changes in DNA?
That’s where chromosomal mutations come in.
Chromosomal mutations are caused by errors in meiosis or mitosis when chromosomes don’t replicate or divide correctly.
We have five chromosomal mutations:
| Chromosomal Muation | Definition | Diagram |
|---|---|---|
| Deletion | A section of a chromosome is deleted |  |
| Duplication | A section of a chromosome is copied and reinserted into the same chromosome |  |
| Inversion | A section of a chromosome is removed, reversed and reinserted |  |
| Translocation | Two chromosome swap sections of their DNA |  |
| Insertion | A section of a chromosome is detached and added to another chromosome |  |
We also have a special case called aneuploidy.
Aneuploidy refers to when someone has an abnormal number of chromosomes – this could be more or less than what they should have.
This is caused by ‘nondisjunction’, which is when chromosomes don’t separate correctly in meiosis I or II.
Monosomy and trisomy are two forms of nondisjunction.
| Types of nondisjunction | Description | Examples |
|---|---|---|
| Monosomy Mono = one | Only one copy of a chromosome when they should have a pair | Monosomy 23 - Turner’s syndrome (only has one X chromosome) |
| Trisomy Tri = three | An extra copy of a chromosome | Trisomy 21 - Down’s syndrome |
Gene Flow and Genetic Drift
Gene flow and genetic drift are another pair of concepts that I find students tend to mix up in Module 6 Biology, but understanding the difference between them is key to achieving those higher marks!
Gene flow refers to the movement of alleles from one population to another, thereby increasing genetic diversity.
There are heaps of examples, but here are some easy ones to remember: bees pollinating flowers from different fields, the mating of different dog breeds or people migrating to a population in a new country.
Genetic drift is the random change of allele frequencies in a population (if you need a recap on allele frequencies, there’s one below).
These changes in allele frequencies can cause organisms to become better suited to their environments, leading to evolution.
There are two kinds of genetic drift:
#1: Founder effect:
This occurs when a small group of individuals break away to start a new population.
The new population will have less variation than the much larger, original population, as there are fewer alleles.
Examples:
- Migration of humans out of Africa or Amish settlers in America.
#2: Bottleneck Effect
This refers to a sharp reduction in a population, typically due to a natural disaster which removes or greatly reduces alleles in a population.
Examples:
- The asteroid impact 66 million years ago wiped out large reptiles like non-avian dinosaurs, but smaller reptiles such as lizards, snakes, and crocodilians survived.
- A typhoon in the 18th century reduced the population of Pingelap Island (Micronesia) to around 20 survivors, leading to a high frequency of genetic disorders like achromatopsia (total colour blindness) in the current population
Allele Frequencies
So we’ve come across the term ‘allele frequencies’ in Module 6 Biology, but what does it even mean?
Allele frequencies refer to the different alleles present in a particular population.
For example, say we have ten individuals in a population and we’re looking at eye colour again.
Since everyone has two alleles for eye colour we have 20 alleles in the population.
Five people have blue eyes and since blue eyes are recessive, we know all these individuals must have two blue alleles each (bb).
The other five people in the population have brown eyes, of which two of these people are heterozygous (Bb) and the other three are homozygous dominant (BB).
- 5 x homozygous recessive = 10 x b
- 2 x heterozygous = 2 x b and 2 x B
- 3 x homozygous = 6 x B
Then we count up how many B and b we have out of the 20 alleles.
Have a go at counting this up yourself and then see if we get the same answer. You can take it one step further by working out its percentage of the allele population.
You should have b x 12 and B x 8. B = 40% and b = 60%.
Now that we’ve gone through gene flow and genetic drift, let’s have a go at consolidating your knowledge by filling out the following table:
If you’re looking for some learning resources for these topics, make sure you check out HSC Together which has FREE video resources on every single HSC Biology dot point so that you can grasp concepts and revise effectively!
Topic 2: Biotechnology
Inquiry question: How do genetic techniques affect Earth’s biodiversity?
In this section under Module 6 Biology, we’ll look at:
- Biotechnologies and past uses
- Willam Farrer: Federation Wheat
- Present uses of Biotechnology
- Bioethics and sample response
Before we begin, we’ll first need to know what biotechnology means.
Biotechnology refers to the human use and manipulation of biological processes and living organisms to improve our quality of life
Essentially, if it involves a biological process that creates something that helps us, then it’s a biotechnology.
Biotechnology: A bit of History…
Humans have used biotechnologies for hundreds of years, typically in agricultural settings.
These included: selective breeding, cross-breeding and fermentation in food production, to produce wine, bread, pickles, cheese and yogurt.
In the late 1800s, Willam Farrer used selective breeding to cross-breed different strains of wheat, in order to produce a wheat variation that would be ideal for the Australian environment.
He used artificial pollination (we’ll go through this in more depth in a second) to achieve this.
- First cross: Etauch (early ripening) x Fife (good baking properties) = Yandilla
- Second cross: Yandilla x Purple Straw 14A (high yield) = Federation
The resulting federation wheat has all the desirable qualities of early ripening, good baking properties and high yield. It was distributed to farmers in 1903.
3 Key Areas of Biotechnology
The Module 6 biology syllabus further separates biotechnologies into three different areas; agriculture, medicine and industry.
- Agriculture: biotechnologies used to improve or assist in the production of food, livestock or plants for harvest.
- Medicine: biotechnologies used to produce/create medicine or improve the lives of individuals.
- Industry: biotechnologies used to create or improve materials used in infrastructure and manufacturing.
But before we dive into biotechnology specifics, we need to go through the ethics of using biotechnologies in these different areas – bioethics.
Bioethics
Ethics are about deciding what is right or wrong and what leads you to that decision.
I like to use the following framework for bioethics:
When it comes to marking an ethics question, there is no right answer.
To score well on these questions, the most important thing is that you have a stance on the issue and evidence to back up your claim.
Here’s an example question:
Now I’m going to show you how you could answer this question based on the ETHICS acronym
A Band 6 response may look like this:
Topic 3: Genetic Technologies
Inquiry question: Does artificial manipulation of DNA have the potential to change populations forever?
In this section under Module 6 Biology, we’ll look at:
- Artificial insemination and artificial pollination
- Advantages and disadvantages with examples
- Whole organism cloning and gene cloning
- Transgenesis and transgenic organisms
This inquiry question focuses on specific examples of biotechnologies and their processes.
Artificial insemination and Artificial Pollination
We’ll start with the processes of artificial insemination and artificial pollination.
Artificial insemination refers to male gametes (sperm) being directly deposited into the female reproductive tract in order to achieve pregnancy.
This process is done for a variety of reasons, including: reducing the risk of injury to females that otherwise occurs during mating, the ease of transporting frozen sperm compared to live exports, and increasing genetic diversity as sperm can be transported far distances.
| Artificial insemination | |
|---|---|
| Description of process | Sperm is deposited into a female’s reproductive system, enabling insemination to occur. |
| Advantages | - Reduces risk of injury to females during the mating process - Animals do not need to be transported across the country, instead relying on frozen sperm - Reduces the need for live exports - Can increase genetic diversity - Enables selective breeding and increases desired traits - Overcome geographical barriers - Save endangered species |
| Disadvantages | - Expensive - Requires specific training and equipment - Disadvantageous alleles could be introduced into the population. - Can result in decreased genetic diversity overtime if the same trait is constantly bred for |
| Examples | - Cows for meat production - Horses for racing - Dairy cattle - selective breeding: jersey x fresian cow, produces a lot of high quality milk - Big cat conservation programs in zoos - tigers and lions |
Meanwhile, you can think of artificial pollination as the ‘plant form’ of artificial insemination.
Pollen contains the male gamete and is taken from the anther, which is dusted onto the female part of the flower, called the stigma.
The male gamete present in the pollen then travels down the style into the ovary of the flower where it fertilises the eggs, making them viable seeds.
Farmers will often remove the anthers of the flower they are pollinating to prevent self-pollination.
| Artificial Pollination | |
|---|---|
| Description of process | Pollen (male gamete) is taken from a male flower and deposited onto the stigma (female part of the flower). Farmers often use a paint brush to do this. |
| Advantages | - Cheap - Enables selective breeding - Overcome geographical barriers - Save endangered species |
| Disadvantages | - Labour intensive - Time consuming - Can result in decreased genetic diversity overtime if the same trait is constantly bred for |
| Examples | - Almonds - Kiwi - Apples - Federation wheat - selectively-bred different wheat varieties |
Whole Organism Cloning
Whole organism cloning seems like something straight out of science fiction, but scientists have managed to make it a reality.
There are two kinds of whole organism cloning you need to know for the HSC: somatic cell nuclear transfer (SCNT) and artificial embryo twinning.
#1: Somatic Cell Nuclear Transfer
Somatic cell nuclear transfer involves three animals: a DNA donor (this will be cloned),an egg donor and a surrogate mother.
An egg cell is taken from a surrogate mother and enucleated, meaning that the nucleus is removed.
A somatic cell (diploid body cell) is taken from the donor sheep and the nucleus (which contains the DNA) is transferred into the enucleated egg.
An electric current is used to fuse the somatic cell nucleus with the enucleated egg cell.
The first animal cloned using SCNT was Dolly the sheep, who died at the age of six due to lung disease.
Cloned animals don’t live as long as their non-cloned friends as the DNA that is used in the transfer will be the same age as the donor.
So if the donor sheep was four years old when the DNA was extracted from it, the new cloned sheep would have DNA that was four years old despite being just born.
#2: Artificial Embryo Twinning
Artificial embryo twinning is a little less complicated than SCNT.
It involves splitting a naturally formed embryo to produce twins.
A fertilised egg is separated into four cells to develop into four separate embryos within four different surrogate mothers.
So, as the four offspring have the same DNA, they would be identical twins of each other.
Gene Cloning
Gene cloning is a way to make lots of copies of a specific gene so we can use it for different purposes.
By isolating the DNA and replicating it, it enables us to solve real-world problems such as creating genetically modified plants and animals, developing new medicines, and even working on treatments like gene therapy.
It also helps scientists study how genes work and figure out their role in diseases.
A common example is using gene cloning to produce insulin for people with diabetes.
I find students often struggle to grasp this complicated process- so if that’s you, you’re not alone.
Below is a simplified step-by-step process of gene cloning, which I teach all my students:
#1: Identify the Gene
- Select the target DNA (gene you want to replicate) from the organism.
- Isolate the target gene using restriction enzymes to create sticky ends.
#2: Prepare the Vector
- Cut a bacterial plasmid using the same restriction enzyme so the stick ends will fit nicely in with one another (like a custom-made puzzle)
- A plasmid is a circular piece of DNA taken typically from bacteria
- We combine the target DNA sequence with an antibiotic resistance gene (I’ll explain why this is important next)
#3: Insert Gene into Vector
- Combine the gene and plasmid with DNA ligase to form recombinant DNA.
- Ligase is like a glue for DNA
#4: Transform Host Cells
- Introduce the plasmid into bacterial cells via heat shock or electric shock.
#5: Select Transformed Cells
- We then grow the bacteria on agar jelly that has an antibiotic.
- Only the bacteria that took up the gene will survive the antibiotics because they have the antibiotic resistance
#6: Clone the Gene
- Allow bacteria to reproduce, replicating the gene.
#7: Verify Cloning
- Use gel electrophoresis or sequencing to confirm the target gene is present.
Applications of Gene Cloning
And, the key to scoring Band 6 responses in HSC Biology is always examples!
I’ve compiled a handy table on the applications of gene cloning to get you started:
| Field | Applications | Examples |
|---|---|---|
| Industrial | Producing enzymes for manufacturing | Enzymes for detergents or food processing. |
| Developing biofuels through engineered microbes | Ethanol production using modified bacteria. | |
| Creating environmentally friendly materials | Bioplastics or biodegradable plastics. | |
| Agricultural | Generating genetically modified crops for higher yields or pest resistance | Bt cotton and pest-resistant corn. |
| Producing crops tolerant to drought or extreme climates | Drought-resistant wheat. | |
| Enhancing nutritional content of food | Golden rice enriched with vitamin A. | |
| Creating disease-resistant livestock or improving growth rates | Cattle resistant to foot-and-mouth disease. | |
| Medical | Producing therapeutic proteins, vaccines, and antibodies | Insulin for diabetes treatment |
| Developing gene therapies for inherited diseases | Insulin for diabetes treatment. | |
| Creating model organisms to study human diseases | Knockout mice for cancer research. | |
| Enabling personalized medicine by analyzing genes linked to diseases or traits | Identifying cancer markers for targeted drugs. |
Yes, this is a challenging module with a lot of content to cover, and it can feel overwhelming at times.
But, you’re not alone—understanding topics like gene cloning, biotechnology, and their applications takes time, effort and lots of practice!
Now that you’ve read through this ultimate Module 6 Biology breakdown, test your understanding here with our complete list of Module 6 practice questions!
Studying for HSC Biology? Access our FREE HSC Biology Study Dashboards backed by thousands of 98+ ATAR scorers in order to keep track of your revision and access free videos for every syllabus dot point!
Wondering where you can find guides to other HSC Biology Modules?
Check out other modules we’ve created guides for below:
- HSC Biology Module 5: Genetic Change
- HSC Biology Module 7: Infectious Disease
- HSC Biology Module 8: Non-Infectious Disease and Disorders
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