Summary notes on Mutations for HSC Biology: Module 6 - Genetic Change.
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Course
Biology
Institution
12th Grade
Well-written summary notes on the topic of Mutations for Module 6 in HSC Biology. Contains relavent vocab to learn, Syllabus dot points and diagrams to help visulise and understand the content.
Terms:
Carcinogenic - capable of causing cancer
Free Radicals - uncharged molecules with one or more unpaired electrons
Induced Mutation - Mutations resulted from mutagenesis
Mutagenesis - Process of inducing a mutation
Mutagens - agents which cause genetic mutation
Mutation - Permanent change to the genetic information in a cell
Pyrimidine dimers - intrastrand DNA cross-link, induced by exposure to ultraviolet light
Syllabus:
Explain how a range of mutagens operate, including but not limited to:
- electromagnetic radiation sources
- chemicals
- naturally occurring mutagens
Introduction
● Mutations are permanent changes to the genetic information in a cell, and may be caused by
mutagens. By changing the genetic material, mutagens can alter the phenotypic. If there is a mutation
in DNA, it will bring change to the polypeptide it codes for, and this may alter cell structure and
function.
● Mutagens are agents which cause genetic mutation. There are three types of mutagens:
- Physical
- Chemical
- Biological
We are exposed to a variety of mutagens on a daily basis; however, our DNA Repair Systems are
usually able to detect changes to the DNA and fix errors.
● Mutations become dangerous when our repair system is compromised. This may lead to disease such
as cancer if the mutation is carcinogenic.
, 6.1.1 Electromagnetic Radiation Sources
● Electromagnetic Radiation is a form of energy which is highly penetrative because it is composed of
high-energy waves. It is able to enter cells, this can cause interference in DNA. Interference by
electromagnetic radiation can cause bonds in DNA to break. This leads to a mutation if the DNA
repair system is unable to correctly repair the change
● Examples of electromagnetic radiation includes:
- Gamma rays
- X-rays
- Ultraviolet light
These radiations are able to disrupt the hydrogen bonds between nitrogenous bases as well as bonding of
the sugar-phosphate backbone.
● Radiation can damage DNA indirectly by ionising molecules to produce free radicals. Free Radicals
are highly reactive because they have a set of unpaired electrons. This can strip away electrons from
the molecules in the DNA, essentially damaging the DNA.
Radiation > Free Radicals (react with DNA) > Causes damage to DNA
● Specific example is UV light. This radiation, although not always harmful, can be damaging in high
doses. Excitation of adjacent pyrimidines (T or C bases) by UV induces the formation of covalent
bonds, called pyrimidine dimers.
6.1.2 Chemicals
● There are chemicals which interact with and have a mutagenic effect on DNA, both directly and
indirectly.
● Radioactive agents, such as uranium, release alpha and beta particles (as well as gamma rays). These
are able to penetrate the cell, interact with DNA bonding and cause disruptions.
● Intercalating agents, such as ethidium bromide, insert or ‘intercalate’ themselves between the
nitrogenous bases, resulting in colour change to the molecule. This can cause frameshift mutations
during DNA replication, making them highly carcinogenic.
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