6.1 Gene Mutation Flashcards
What is a mutation?
Change to the quantity or structure of DNA
What are the 2 types of mutation?
Gene/point
Chromosome
When can a mutation be inherited?
If it occurs in a gamete
How can the rate of mutation be increased?
Mutagens - certain chemicals or ionising radiation
What does the natural rate of mutation depend on?
The species and locus of gene
What is the usual rate in plants and animals?
1 in 100000 per locus per generation
(Point) where do point mutations occur?
Single locus of a chromosome
(Point) what can a change result in?
Change in DNA bases Change in MRNA bases Change in MRNA codon Change in amino acids Change in protein structure Change in protein function Change in cell function
(Point) what are 3 types of mutation?
Substitution
Deletion
Insertion
(Point) what occurs in substitution and what is its effect?
One base changed for another
Only affects one amino acid
Rest of the protein is unaffected
(Point) what occurs in deletion and what is its effect?
Base is removed
Frame shift occurs
The rest of the protein is wrong
(Point) what occurs in insertion and what is its effect?
A base is added
Frame shift occurs
Rest of the protein is wrong
What is a genotype?
Set of genes in DNA responsible for a particular characteristic
What is a phenotype?
Physical expression of a characteristic
(Effects) why do some mutations have no effect on the phenotype of an organism?
Normally functioning proteins are still synthesised
(Effects) what happens when a mutation has a damaging effect?
Negative effect
Proteins are no longer synthesised or are not functional
Interfering with essential processes
(Effects) what happens when a mutation is beneficial?
Produces a new useful characteristic
(Effects) give an example of a beneficial mutation:
Mutation in protein present in cell membranes prevents HIV binding so the person is immune
What is loss of a purine base?
Depurination
What is loss of a pyramidine base?
Depyrimidination
(Mutagen) give an example of a physical mutagen:
Ionising radiation
(Mutagen) what does ionising radiation do/ how does it result in mutation?
Breaks DNA strands - some breaks can be repaired but mutations occur in the process
(Mutagen) give an example of a chemical agent:
Deaminating agents
(Mutagen) what effects do deaminating agents have/ how do they cause mutation?
Chemically alter DNA bases e.g. Converting cytosine to uracil
(Mutagen) give examples of biological agents:
Alkylating agents
Base analogs
Viruses
(Mutagen) what effect do alkylating agents have?
Methyl or ethyl groups attached to bases resulting in incorrect base pairing
(Mutagen) what effect do base analogs have?
Incorporated into DNA replacing a base thus changing the sequence
(Mutagen) what effect do viruses have?
Viral DNA insets itself into the genome changing the base sequence
(Effects) what effect do silent mutations have?
No effect on phenotype they don’t change the proteins or activity
(Effects) why don’t silent mutations have an effect?
Found in introns
Code for same amino acid (degenerate)
Change primary structure but not whole protein
(Effects) what do nonsense mutations result in a codon becoming? What is its effect?
A stop codon
Results in shortened protein
(Effects) what does a missense mutation result in?
Incorporation of incorrect amino acid into primary structure where protein is synthesised
(Effects) what does the effect of the missense mutation depend on?
The structure and function of the protein made
(Effects) what is a conservative mutation?
Amino acid change leads to another amino acid coding for having similar properties
(Effects) what is a non conservative mutation?
New amino acid has different properties to the original
More likely to affect the structure and cause disease
(Effects) what is a amorph?
Mutation resulting in loss of function of a protein
(Effects) what is a hypomorph?
Mutation resulting in reduction in function of protein
(Effects) what is a hypermorph?
Mutation resulting in gain in function
(Effects) what do amorphic mutations result in?
Recessive alleles
(Sickle cell anaemia) what happens to the erythrocytes and why?
Develop abnormally due to mutation in gene coding for haemoglobin
(Sickle cell anaemia) thymine replaces adenine making the sixth amino acid what instead of what?
Valine instead of glutamic acid
(Sickle cell anaemia) in homozygous individuals what is there?
Two copies of the gene for sickle cell anaemia
(Sickle cell anaemia) in heterozygous individuals what is there? What is special about these individuals?
One copy - carriers
They can get mild symptoms, however they are resistant to malaria
(Chromosome) what do chromosome mutations affect?
Whole chromosome or a no of chromosomes
(Chromosome) what is deletion?
Section of chromosome breaks off and is lost in cell
(Chromosome) what happens in duplication?
Sections/genes get duplicated on chromosome
(Chromosome) what is translocation?
Section of one chromosome breaks off and joins to another chromosome
(Chromosome) what is inversion?
Section of a chromosome breaks off, is reversed, then joins back to the chromosome
(Chromosome) what so polysomy?
Gain extra copy of a whole chromosome
(Chromosome) what is polyploidy?
Gain extra set of all chromosomes