Mutations Flashcards
What is a mutation?
Change in the genetic code of an allele
How can mutations happen?
As cells divide (for growth, repair, maintenance) and miss checkpoints during mitosis
What can mutations be caused by?
- Environmental agents
- Chemicals
- Errors in the genetic code
What can mutations be?
Negative, positive or neutral
What are the two main types of mutations?
-Point Mutations
-Chromosomal Mutations
What are Point Mutations?
Failure by the replicating cell to copy the genetic information accurately:
-Base pair substitutions
- Insertions
- Deletions
What are the three types of Point Mutations? Describe them.
- Base-pair Substitutions
One nitrogenous base is accidentally replaced with a different base - Insertions
One or more nitrogenous bases is inserted during the copying process - Deletions
One or more nitrogenous bases is deleted during the copying process
What are chromosomal mutations?
Errors that involve an entire chromosome or large part of a chromosome
What is an example of a chromosomal mutation? What are examples of those?
Non-disjunction
- Down Syndrome
- Short stature
- Heart defects
- Developmental delays
What are other examples of Chromosomal Mutations?
- Large scale deletions, insertions, or inversion (flipping) of entire portions of a chromosome (contain thousands of bases).
Where do most mutations occur?
In the parts of the DNA that do not code for genes
What happens to many mutations that occur?
They are often quickly repaired, but as organisms age, mitosis occurs more frequently leading to higher chance of mutations (cancer)
Where do the mutations occur that are not passed on to offspring?
In body cells (autosomes)
Where do the mutations occur that can be passed on to offspring? Why does this happen? (3 points)
- In sex cells (gametes)
- DNA that mutates in the egg or sperm becomes part of the DNA in the zygote if fertilization takes place
- This means that the new individual will have a copy of the mutation in every cell of its body and will be able to pass the mutation on
What happens if a mutation is dominant?
- Could be expressed phenotypically in the 1st generation
- i.e. Huntington’s disease
What happens if a mutation is recessive?
- Likely will not be expressed for many generations until by chance, two individuals with same mutation produce a homozygous recessive mutation in the offspring
-Cystic Fibrosis
Describe the mutation of Sickle-Cell Anemia
- Both harmful and beneficial
- Inherited a mutated gene where adenine is substituted by thymine
- Red blood cells (usually round) become C-shaped (causes movement through blood vessels to be obstructed)
- Blood flow is impaired and cells must be removed and destroyed
- Can be painful, increased risk of infection
- SCA can also have a positive property as well
- Fighting malaria
- Malaria parasite enters the blood, but since the person is affected by SCA, the cells sickle when oxygen is low and cells are destroyed
Describe the mutation of Lactose Intolerance and Tolerance
- Lactose tolerant individuals contain a mutation and will continue to produce the enzyme for digestion
- All individuals are born lactose intolerant
What are spontaneous mutations?
- Happen by accident in nature
- Result of incorrect copying of DNA during mitosis and meiosis
What are induced mutations?
- Result of exposure to a physical or chemical agent
- Cigarette smoke, radiation
