GCSE Biology - What are DNA Mutations? #67
Summary
TLDRThis educational video delves into DNA mutations, explaining how changes in the DNA sequence can occur spontaneously or be triggered by carcinogens and radiation. It outlines the structure of genes and proteins, highlighting how a mutation can alter an amino acid sequence, potentially affecting protein shape and function. The video also touches on non-coding DNA's role in gene expression and distinguishes between three types of mutations: substitutions, insertions, and deletions, emphasizing their varying impacts on genetic code and protein synthesis.
Takeaways
- 𧏠**Mutation Defined**: A mutation is a change in the DNA base sequence, such as a C changing to a G.
- đ **Spontaneous Mutation**: Mutations naturally occur in cells, especially during DNA replication before cell division.
- đ **Carcinogens and Radiation**: Exposure to harmful chemicals like those in cigarette smoke and certain types of radiation can increase the risk of mutations.
- đ **Not All Exposures Cause Mutations**: While carcinogens and radiation increase risk, they do not guarantee mutations will occur.
- 𧏠**DNA and Genes**: A gene is a section of DNA that codes for a protein, with each group of three bases (codon) coding for an amino acid.
- đ **Protein Synthesis**: The sequence of codons determines the sequence of amino acids that fold to form a protein.
- â ïž **Impact of Mutations**: A mutation can alter the amino acid sequence, potentially changing the protein's shape or function.
- đ **Enzyme Function**: If a protein is an enzyme, a mutation might affect its active site, preventing it from catalyzing reactions.
- đ **Most Mutations Are Harmless**: Many mutations have little effect because they only slightly alter proteins or occur in non-coding DNA.
- 𧏠**Non-Coding DNA**: Non-coding DNA does not code for proteins and its function is not fully understood, but some plays a role in gene expression.
- đ **Gene Expression**: Genes can be turned on or off, like the hemoglobin gene in nerve cells which is not expressed.
- đ **Types of Mutations**: There are three main types of mutations - substitutions, insertions, and deletions - each affecting the DNA sequence differently.
Q & A
What is a mutation?
-A mutation is a change in the DNA base sequence, which can alter the letters that make up the DNA code. This can occur spontaneously or due to certain external factors.
What are some factors that increase the risk of mutations?
-Two main factors that increase the risk of mutations are carcinogens, such as those found in cigarette smoke, and certain types of radiation, including x-rays and gamma rays.
What is a gene, and how does it relate to proteins?
-A gene is a section of DNA that codes for a protein. It does so by using sequences of bases (called codons or triplets) that correspond to amino acids, which are the building blocks of proteins.
How can a mutation in a gene affect the protein it codes for?
-A mutation can change the sequence of amino acids that make up a protein, potentially altering its shape or function. For example, if the protein is an enzyme, the mutation might prevent it from binding to its substrate, making it unable to catalyze a reaction.
Do all mutations have significant effects on the body?
-No, most mutations do not have significant effects. Many mutations only slightly alter the protein or occur in non-coding DNA, which doesnât directly affect gene expression.
What is non-coding DNA, and why is it important?
-Non-coding DNA is DNA that doesn't code for proteins. While much of it has no known function, some of it plays a crucial role in regulating gene expression, controlling whether certain genes are turned on or off.
What are the three main types of mutations?
-The three main types of mutations are substitutions, insertions, and deletions. Each type involves different changes to the DNA sequence and can affect proteins in various ways.
What happens in a substitution mutation?
-In a substitution mutation, one base in the DNA sequence is replaced with another, which can result in a different amino acid being coded, potentially altering the protein.
How does an insertion mutation differ from a substitution mutation?
-In an insertion mutation, an extra base is added to the DNA sequence, which shifts all subsequent bases and codons. This can result in a more dramatic change in the amino acid sequence and protein structure than a substitution mutation.
What occurs in a deletion mutation?
-In a deletion mutation, a base is removed from the DNA sequence, causing all subsequent bases and codons to shift, similar to an insertion. This can greatly alter the amino acid chain and the resulting protein.
Outlines
𧏠Understanding DNA Mutations
This paragraph explains what mutations are in the context of DNA, which are changes in the DNA base sequence. It highlights that these changes occur spontaneously, especially during DNA replication, and can be influenced by external factors like carcinogens and certain types of radiation. The explanation clarifies that while these factors increase the risk, they do not guarantee mutations. The paragraph also provides a brief overview of DNA's function, describing genes as sections of DNA that code for proteins. It explains how a sequence of bases, or codons, determines the sequence of amino acids that form proteins. The paragraph further discusses how mutations can alter the amino acid sequence, potentially changing the protein's shape or function, and gives an example of how an enzyme's active site might be affected. It concludes by noting that most mutations have little effect, either because they only slightly alter the protein or because they occur in non-coding DNA, which doesn't code for proteins but can play a role in gene expression.
đ Types of DNA Mutations
The second paragraph delves into the three specific types of DNA mutations: substitutions, insertions, and deletions. It describes a substitution mutation as a change where one base is replaced with another, which can alter the coded amino acid. The paragraph emphasizes that insertion mutations are more disruptive because they add an extra base to the sequence, causing a shift in all subsequent bases and altering the amino acid chain significantly. Similarly, deletion mutations remove a base, leading to a shift that changes all following codons. The summary points out the severity of insertion and deletion mutations compared to substitutions, due to their broader impact on the genetic code. The paragraph concludes the video with a call to action for viewers to like and subscribe for more content.
Mindmap
Keywords
đĄMutation
đĄDNA
đĄCarcinogens
đĄRadiation
đĄGene
đĄTriplet or Codon
đĄAmino Acids
đĄProtein
đĄNon-coding DNA
đĄGene Expression
đĄSubstitutions
đĄInsertions
đĄDeletions
Highlights
Today's video is about mutations, covering what causes them and their consequences.
Mutations are changes in the DNA base sequence.
DNA mutations occur spontaneously, especially during DNA duplication before cell division.
Carcinogens in cigarette smoke and certain types of radiation increase the risk of mutations.
Mutations don't always occur, they just increase the risk.
A gene is a section of DNA that codes for a protein.
Each group of 3 bases, called a codon, codes for one of the 20 amino acids.
A mutation can change the amino acid that a codon codes for, affecting protein formation.
Most mutations have no significant effect because they only slightly affect the protein.
Most mutations occur in non-coding DNA, which doesn't code for proteins.
Non-coding DNA plays a role in gene expression, turning genes on or off.
Gene expression is crucial for cell-specific protein production.
There are three specific types of mutations: substitutions, insertions, and deletions.
Substitution mutations occur when one base is changed for another.
Insertion mutations involve adding an extra base, which can significantly alter the protein sequence.
Deletion mutations occur when a base is removed, also altering the protein sequence.
The video concludes with a call to like and subscribe for more content.
Transcripts
Oh
you
today's video is all about mutations so
we'll cover what causes mutations and
what some of their consequences can be
now all we mean by mutation is a change
in the DNA base sequence so a change in
a sequence of letters that make up our
DNA code like in this example here where
this C has been changed to a G
these mutations happen spontaneously in
our cells all the time particularly when
DNA is being duplicated before cell
division like in mitosis two things that
increase their risk of mutations though
are carcinogens which a group of harmful
chemicals like you get in cigarette
smoke and certain types of radiation
like x-rays or gamma rays it's important
to understand though that these things
don't always cause mutations they just
increase the risk of a mutation
occurring
to understand how mutations affect our
body we need to quickly recap how DNA
works if we think of a gene which is
just a section of DNA that codes for
protein then all it really is is a
particular sequence of bases each group
of 3 bases is called a triplet or a
codon and codes for one of the 20
different amino acids so this codon here
ACC might code for amino acid 7 while
there's other one
CTA could code for amino acid 18
by doing this for all of the triplets
and then combining the amino acids
together in the correct order we create
a long chain of amino acids which can
then fold up by itself to form a protein
you
but if this piece of DNA had a mutation
for example this G here changed to a tee
then the amino acid that this codon
codes for might change as well and this
small change can have lots of knock-on
effects
this is because the overall sequence of
amino acids who had now be different and
so the protein that it ends up forming
would be different as well meaning that
it can have a different shape or
function
for example if this protein was an
enzyme then the mutation might change
the shape or the enzymes active site so
they can't fit the substrate anymore
this would mean that it can't form an
enzyme substrate complex and so it
couldn't catalyze the reaction
most of the time though a mutation
doesn't have any significant effect this
is because they'll often only affect a
protein very slightly so it might look a
tiny bit different but it still works in
basically the same way also most
mutations occur in what we call
non-coding DNA which isn't part of any
gene and so it doesn't code for protein
most of this non-coding DNA doesn't seem
to do anything at all and we're not
really sure why we have so much of it
but some of it does play an important
role in the expression of genes which is
whether those genes are turned on or off
for example if we think of a nerve cell
there's no need for it to produce
hemoglobin because hemoglobins only
needed by red blood cells so in the
nerve cell the gene for hemoglobin will
be switched off which is the same thing
as saying that it won't be expressed
you
the last thing we need to cover are the
three specific types of mutations
substitutions insertions and deletions
if we take this DNA sequence as an
example let's start with a substitution
mutation which is when one of the basis
is changed or substituted for another
random base like if there's a change to
a T or this G changed to an A as we saw
earlier the problem with this is that it
changes the code on that basis in and so
it could change the amino acid that it
codes for
now an insertion mutation is a bit
different this time an extra base is
inserted into the sequence somewhere for
example if a c was inserted in here
between the T and the a of CTA then this
codon would change from CTA to CTC
because the a has been pushed along to
the next codon this feature means that
these mutations are actually a lot worse
than substitution mutations are because
it means that all the subsequent bases
are shifted along by one which alters
all of the subsequent columns and so the
amino acid chain after that point would
be completely different
you
a similar thing happens with deletion
mutations which is where one of the
bases is deleted from a sequence for
example if this T gets deleted that our
DNA will look like this because the T's
been removed this a has now shifted one
space to the left a hand as a result all
of these spaces will also have shifted
one space to the left so as well as this
codon being different
all of these subsequent ones will be as
well
anyway that's everything for today's
video so if you found it useful then
please do give us a like and subscribe
and we'll see you again soon
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