19 - Genetics Of Living Systems Flashcards
Define a mutation
A change in the sequences of bases in DNA
What causes the change in sequence in a mutation?
Deletion, substitution or insertion
What is it called if only one nucleotide is affected by a mutation?
A point mutation
The substitution of a single nucleotide causes what to occur?
Changes the codon, so a new a.a. is coded, changing the 1Y of the protein
How can substitution not actually affect the protein?
Due to degenerate nature of code, the new codon may still code for the same a.a.
What does the insertion or deletion of a nucleotide(s) cause!
Frameshift mutation
What is the reading frame of a sequence of bases?
The triplet code that transcribes consecutively in non-overlapping groups of 3
How many bases equals an amino acid?
3 bases
What does the addition or deletion of nucleoside do!
Shifts the reading frame of the sequence of bases, changing every successive codon from the point of mutation
In what circumstance would the reading frame not be changed in addition or deletion?
If the multiples of 3 correspond to fill codons
What does it mean if a mutation has no effect?
The phenotype isn’t changed and normal functioning proteins are synthesised
What does it mean if a mutation is damaging?
The phenotype of an organism is affected in a negative way which can interfere with essential processes
What does it mean if a mutation is beneficial?
The mutation provides a useful characteristic to improve survival
What is a mutagen?
A chemical, physical, or biological agent which causes mutations
How are mutations described?
As spontaneous
What does the mutation of an absence of a base lead to?
The insertion of an incorrect base through complementary base pairing during DNA replication
What are free radicals?
Oxidising agents
What can free radicals do to nucleotides?
Affect their structure and disrupt base pairing
Why are antioxidants known as anti carcinogenic?
Due to their ability to negate the effects of free radicals
What are silent mutations?
They have no effect on the phenotype of an organism
What are nonsense mutations?
These reused in a codon becoming a STOP codon instead of an amino acod
What are missense mutations?
This results in the incorrect amino acid in the 1Y
Beneficial Mutations
Where is the ability to digest lactose most commonly found?
In European populations who are more likely to farm cattle
Beneficial Mutations
The majority of mammals become lactose intolerant after they what?
Cease to suckle
Where do gene mutations occur?
In single genes or sections of DNA
Where do chromosome mutations affect?
The whole chromosome or number of chromosomes in a cell
What normally causes chromosome mutations?
Caused by mutagens normally in meiosis
Chromosome mutations
How does deletion change chromosome structure?
Section of chromosomes breaks off and is lost
Chromosome mutations
How does duplication affect?
Sections get duplicated on a chromosome
Chromosome mutations
How does translocation affect chromosome structure?
A section of one chromosome breaks off and joins another non-homologous chromosome
Chromosome mutations
How does inversion affect the chromosome structure?
A section breaks off, is reversed, and joins back onto the chromosome
