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Unlock This CourseMutations are changes in the DNA sequence that can happen naturally or be caused by external factors. Think of DNA as a recipe book for making you - sometimes there are typos in the recipe! These changes can be passed down from parents to children, affecting how traits are inherited. Understanding mutations helps us learn about genetic diseases, evolution and why we're all unique.
Key Definitions:
Mutations can happen spontaneously during DNA copying or be caused by external factors called mutagens. These include UV radiation from the sun, chemicals in cigarettes, X-rays and certain viruses. Most mutations occur naturally at a rate of about 1 in every 10 million DNA bases copied.
Not all mutations are the same. They can be classified by their size, location and effect on the organism. Understanding these different types helps us predict their impact on inheritance patterns.
These are the smallest type of mutation, affecting just one DNA base. Imagine changing one letter in a word - sometimes it makes no difference, sometimes it completely changes the meaning!
The DNA change doesn't affect the protein made. Like changing "colour" to "color" - different spelling, same meaning.
One amino acid in the protein is changed. This might alter how the protein works, like changing one ingredient in a recipe.
Creates a "stop" signal too early, making a shortened, usually non-functional protein. Like ending a sentence mid-way.
These involve larger changes to chromosomes, affecting multiple genes at once. They can occur during cell division when chromosomes don't separate properly.
Deletion removes a section of chromosome, whilst duplication creates extra copies. Both can disrupt normal gene function and cause genetic disorders.
This genetic condition is caused by a single point mutation in the gene for haemoglobin. The mutation changes just one amino acid, but this causes red blood cells to become sickle-shaped instead of round. People with two copies of this mutation have sickle cell disease, but those with one copy are actually protected against malaria - showing how mutations can be both harmful and beneficial!
Mutations can be inherited in different ways depending on where they occur and whether they're dominant or recessive. Understanding these patterns helps predict the likelihood of genetic conditions appearing in families.
The location where a mutation occurs determines whether it can be passed to offspring. This is crucial for understanding inheritance patterns.
These occur in reproductive cells (sperm or eggs) and can be passed to children. Every cell in the offspring will carry this mutation, making it heritable.
These happen in body cells after birth and cannot be inherited. They might cause problems for the individual but won't affect their children.
Genetic mutations follow predictable patterns when passed from parents to children, depending on whether they're dominant or recessive.
Only one copy of the mutated gene is needed to show the trait. If one parent has it, there's a 50% chance each child will inherit it.
Two copies of the mutated gene are needed. Both parents must be carriers for a child to be affected (25% chance).
The mutation is on the X chromosome. Males are more likely to be affected because they only have one X chromosome.
This neurological condition is caused by a dominant mutation, meaning you only need one copy from either parent to develop the disease. The mutation involves too many repeats of a DNA sequence, like a record getting stuck. Symptoms usually appear in middle age and there's currently no cure, making genetic counselling important for affected families.
Mutations are the raw material for evolution, providing the genetic variation that natural selection acts upon. Without mutations, all organisms would be identical and unable to adapt to changing environments.
Some mutations provide advantages that help organisms survive and reproduce better. These positive changes can spread through populations over time.
Most mammals lose the ability to digest milk after weaning, but mutations in some human populations allow adults to continue producing lactase enzyme. This was advantageous in dairy-farming societies.
Not all mutations have dramatic effects. Many are neutral, causing no noticeable change, whilst others can be harmful and reduce survival chances.
These don't affect survival or reproduction. They accumulate over time and help scientists track evolutionary relationships between species, acting like a molecular clock.
During the Industrial Revolution, a mutation causing dark colouration in peppered moths became advantageous. On soot-covered trees, dark moths were better camouflaged than light ones, so they survived better and reproduced more. When pollution decreased, the light form became common again, showing how environmental changes can make mutations helpful or harmful.
Understanding mutations and inheritance helps families make informed decisions about genetic risks. Genetic counsellors use family history and DNA tests to assess the likelihood of inherited conditions.
By studying family trees and understanding inheritance patterns, scientists can calculate the probability of genetic conditions appearing in future generations.
These diagrams help predict the likelihood of offspring inheriting specific traits or genetic conditions based on their parents' genotypes.
Today, genetic testing can identify many mutations before symptoms appear. This allows for early treatment, lifestyle changes, or family planning decisions. Gene therapy, where healthy genes are introduced to replace faulty ones, offers hope for treating some genetic conditions in the future.