Mutations Flashcards
Chapter 1.5
What are mutations?
Permanent changes in the base sequence(s) of a DNA molecule, and can result in changes to the structure and function of proteins by coding for a different amino acid sequence than intended.
How do mutations differ from changes in gene expression?
Changes to gene expression does not alter the sequence of bases, instead limiting expression of the gene into a protein only.
What are germline mutations?
Occurs in gametes (sex cells), and can be transmitted to offspring and every cell in the offspring will have the mutation.
What are somatic mutations?
Occurs in other cells of the body that are not gametes. May have little effect on the organism since they are confined to just one cell and its daughter cells; it cannot be passed onto its offspring.
How do environmental factors affect mutations?
Whilst the environment can cause or change rates of mutations, the environment does not direct the changes.
What biological factor can cause a mutation to occur?
Random collisions between the DNA and other molecules (higher temperatures means more collisions) or mistakes during DNA replication. The bond between purines (A and G) and the sugar is slightly unstable, meaning that they can be lost through collision.
What is a base-pair insertion/deletion?
A nucleotide base-pair is either deleted or inserted into the DNA strand. This results in a frameshift, where all the codons following the mutation are altered, and likely the amino acids that are coded for.
What is a point mutation?
Change in a single nucleotide in DNA; can be either silent, missense or nonsense.
What is a silent point mutation?
Mutated codons codes for the same amino acid. Effect: none.
What is a missense point mutation?
Mutated codons codes for a different amino acid. Effect: variable.
What is a nonsense mutation?
Mutated codon is a premature stop codon. Effect: serious.
In regard to large scale mutations affecting chromosomes, what is deletion?
Genetic material breaks off from a section of the chromosome and is lost.
In regard to large scale mutations affecting chromosomes, what is duplication?
Genetic material is duplicated and extra copies of genes are found on the chromosome.
In regard to large scale mutations affecting chromosomes, what is translocation?
A section of one chromosome detaches and moves to a new chromosome.
In regard to large scale mutations affecting chromosomes, what is inversion?
A section of broken chromosome is inserted back but the segment is reversed during the process.
In regard to large scale mutations affecting chromosomes, what is insertion?
A section of DNA from one chromosome may be removed and added to another chromosome.
What are mutagens?
Rates of mutation can be increased by physical, chemical or biological factors.
What are examples of mutagens?
Ionising radiation, mutagenic chemicals, heat and viruses.
How does ionising radiation influence mutations?
The most common psychical agents are high-energy radiation like X-rays (creates ions which break sugar-phosphate backbones or base pairs in DNA) or ultraviolet light (creates bonds between DNA bases that would not normally exist).
How do mutagenic chemicals influence mutations?
Chemicals in the environment can cause chemical changes to particular bases, mimic the shape of normal bases and thus disrupt the DNA replication process, disrupt cell division leading to chromosomal errors, or cause direct damage to chromosomes which may lead to breaks.
What are some examples of chemical mutagens?
Cigarette smoke, asbestos, benzene (in petrol), vinyl chloride (in plastics), etoposide (chemotherapy drug).
How does excess heat influence mutations?
By increasing the frequency of collisions between DNA and other molecules.
How do viruses influence mutations?
Since viruses inject their DNA or RNA material into a host cell which then incorporates with the host genetic material, they may biologically induce substitution, insertion or deletion mutations.
What is a positive effect of mutations?
Mutations are the source of new genes and changes in phenotype which provide a source of variation on which natural selection can act.
How are all living things related?
The mechanism for converting DNA into proteins is the same, and DNA is universal, meaning it can be transferred between different species. This provides supporting evidence that all living things came from a common ancestor.
When are mutations most likely to occur?
During cell division/DNA replication.
