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22 Dec 2025
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Higher Human Biology: Understanding Unit 1
A
Anna Riddell
@annariddell_umtg
Cell Types and Differentiation
Your body is made up of two main types of cells that do completely different jobs. Somatic cells are basically every cell in your body except the ones involved in making babies - these divide through mitosis to create more identical copies. Then you've got germ cells (sperm and eggs) which use a special type of division called meiosis.
Here's where it gets really clever: cellular differentiation is how a generic cell decides what it wants to be when it grows up. Each cell switches on specific genes to make the proteins it needs for its particular job, whether that's being a muscle cell, brain cell, or skin cell.
Stem cells are the ultimate multitaskers - they're unspecialised cells that can become any type of cell your body needs. Embryonic stem cells are pluripotent (can become any cell type), whilst tissue stem cells are multipotent (more limited options). They're already helping treat diseases like leukaemia through bone marrow transplants and healing burns with skin grafts.
Quick Tip: Think of stem cells like blank canvases that can be painted into any picture your body needs!
DNA Replication and PCR
When your cells need to divide, they first have to make a perfect copy of all your DNA - no pressure there! DNA polymerase is the star enzyme that adds new nucleotides using complementary base pairing, but it can only work in one direction (5' to 3').
This creates a bit of a problem because DNA strands run in opposite directions. The solution? One strand (the leading strand) gets copied smoothly, whilst the other (lagging strand) has to be made in fragments that get joined together by ligase enzyme.
Scientists have cleverly copied this process in the lab with PCR (Polymerase Chain Reaction). Using a thermocycler, they heat DNA to separate strands, cool it so primers can attach, then warm it up again for heat-resistant DNA polymerase to do its thing. This can solve crimes and diagnose diseases by amplifying tiny DNA samples.
Mutations and Cancer
Not all changes to DNA are bad, but some can cause serious problems. Mutations are changes that can result in altered or missing proteins. You might see translocation (chromosome sections swapping places), deletion (bits going missing), inversion (sections flipping around), or duplication (extra copies appearing).
Cancer cells are basically cells that have forgotten the rules - they divide excessively and ignore the body's stop signals. This creates tumours that can spread and form secondary tumours elsewhere in the body.
Frame shift mutations (from inversions and deletions) are particularly nasty because they change all the amino acids that come after the mutation. Single gene substitutions can cause missense (wrong amino acid), nonsense (early stop signal), or splice site mutations that mess up RNA processing.
Transcription and Translation
Making proteins from DNA is like following a recipe, but it happens in two stages. Transcription occurs in the nucleus where RNA polymerase unwinds DNA and creates a primary mRNA transcript containing both introns (junk) and exons (useful bits).
RNA splicing removes the introns, and here's something brilliant: alternative RNA splicing means one gene can make different proteins depending on which exons get kept. It's like having one recipe that can make different dishes!
Translation happens at ribosomes where tRNA molecules bring amino acids to match up with codons on the mRNA. Each tRNA has an anticodon that pairs with the codon, and peptide bonds link the amino acids together to form proteins. The tRNA then gets recycled for the next round.
Remember: DNA → RNA → Protein is the central dogma of biology - master this flow and you'll understand how life works!
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Most popular content: Transcription
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Anna
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Thomas R
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Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
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This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
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The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
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In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
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very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
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I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Higher Human Biology: Understanding Unit 1
A
Anna Riddell
@annariddell_umtg
Ever wondered how your body creates millions of different cells from just one fertilised egg? This is all about the incredible processes of cell division, DNA replication, and protein synthesis that keep you alive and growing every single day.
Cell Types and Differentiation
Your body is made up of two main types of cells that do completely different jobs. Somatic cells are basically every cell in your body except the ones involved in making babies - these divide through mitosis to create more identical copies. Then you've got germ cells (sperm and eggs) which use a special type of division called meiosis.
Here's where it gets really clever: cellular differentiation is how a generic cell decides what it wants to be when it grows up. Each cell switches on specific genes to make the proteins it needs for its particular job, whether that's being a muscle cell, brain cell, or skin cell.
Stem cells are the ultimate multitaskers - they're unspecialised cells that can become any type of cell your body needs. Embryonic stem cells are pluripotent (can become any cell type), whilst tissue stem cells are multipotent (more limited options). They're already helping treat diseases like leukaemia through bone marrow transplants and healing burns with skin grafts.
Quick Tip: Think of stem cells like blank canvases that can be painted into any picture your body needs!
DNA Replication and PCR
When your cells need to divide, they first have to make a perfect copy of all your DNA - no pressure there! DNA polymerase is the star enzyme that adds new nucleotides using complementary base pairing, but it can only work in one direction (5' to 3').
This creates a bit of a problem because DNA strands run in opposite directions. The solution? One strand (the leading strand) gets copied smoothly, whilst the other (lagging strand) has to be made in fragments that get joined together by ligase enzyme.
Scientists have cleverly copied this process in the lab with PCR (Polymerase Chain Reaction). Using a thermocycler, they heat DNA to separate strands, cool it so primers can attach, then warm it up again for heat-resistant DNA polymerase to do its thing. This can solve crimes and diagnose diseases by amplifying tiny DNA samples.
Mutations and Cancer
Not all changes to DNA are bad, but some can cause serious problems. Mutations are changes that can result in altered or missing proteins. You might see translocation (chromosome sections swapping places), deletion (bits going missing), inversion (sections flipping around), or duplication (extra copies appearing).
Cancer cells are basically cells that have forgotten the rules - they divide excessively and ignore the body's stop signals. This creates tumours that can spread and form secondary tumours elsewhere in the body.
Frame shift mutations (from inversions and deletions) are particularly nasty because they change all the amino acids that come after the mutation. Single gene substitutions can cause missense (wrong amino acid), nonsense (early stop signal), or splice site mutations that mess up RNA processing.
Transcription and Translation
Making proteins from DNA is like following a recipe, but it happens in two stages. Transcription occurs in the nucleus where RNA polymerase unwinds DNA and creates a primary mRNA transcript containing both introns (junk) and exons (useful bits).
RNA splicing removes the introns, and here's something brilliant: alternative RNA splicing means one gene can make different proteins depending on which exons get kept. It's like having one recipe that can make different dishes!
Translation happens at ribosomes where tRNA molecules bring amino acids to match up with codons on the mRNA. Each tRNA has an anticodon that pairs with the codon, and peptide bonds link the amino acids together to form proteins. The tRNA then gets recycled for the next round.
Remember: DNA → RNA → Protein is the central dogma of biology - master this flow and you'll understand how life works!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
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Is Knowunity really free of charge?
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Most popular content: Transcription
Most popular content in Biology
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user