What is a gene mutation?
Enjoying Flashcards?
Tell us what you think
What is a gene mutation?
A gene mutation is a structural change in the sequence of base pairs in a DNA molecule, potentially resulting in a new allele.
Define substitution mutation.
A substitution mutation occurs when a nucleotide base in the DNA sequence is randomly swapped for a different base.
What is an insertion mutation?
An insertion mutation occurs when a nucleotide with a new base is randomly inserted into the DNA sequence, causing a frameshift.
Define a deletion mutation.
A deletion mutation is when a nucleotide is randomly deleted from the DNA sequence.
True or False?
Deletion mutations can cause a frameshift in the DNA sequence.
True.
Deletion mutations can cause a frameshift (where the mutation has a knock-on effect by changing the triplets of bases), altering the amino acid sequence.
True or False?
A substitution mutation can have a knock-on effect on the rest of the DNA sequence.
False.
A substitution mutation will only change the amino acid for the triplet in which the mutation occurs; it will not have a knock-on effect on the rest of the sequence.
What are single nucleotide polymorphisms (SNPs)?
SNPs are differences in a single DNA nucleotide, such as replacing cytosine (C) with thymine (T) in a certain stretch of DNA.
True or False?
SNPs are only found in the coding regions of DNA.
False.
SNPs are commonly found in the non-coding regions of DNA between genes.
What are the three forms of substitution mutations?
The three forms of substitution mutations are silent mutations, missense mutations, and nonsense mutations.
True or False?
Insertions and deletions only affect the amino acid coded for by the mutated triplet.
False.
Insertions and deletions can cause a frameshift, altering the triplet grouping and affecting the entire amino acid sequence downstream.
Define frameshift mutation.
A frameshift mutation is caused by insertions or deletions of nucleotides that shift the reading frame of the mRNA, altering the entire amino acid sequence after the mutation site.
How do insertions and deletions lead to frameshift mutations?
Insertions and deletions add or remove nucleotides, disrupting the triplet grouping of codons and shifting the reading frame.
What is the effect of a frameshift mutation on a polypeptide?
A frameshift mutation can dramatically change the amino acid sequence (because the codon sequence is changed within the DNA), potentially causing the polypeptide to cease functioning.
Why are insertions and deletions often more harmful than substitution mutations?
Insertions and deletions are often more harmful than substitution mutations they can cause frameshift mutations, which alter the entire amino acid sequence downstream, potentially disabling the protein.
How does a frameshift mutation alter the amino acid sequence?
A frameshift mutation alters the amino acid sequence because it shifts the reading frame, causing the ribosome to read different codons, resulting in incorrect amino acids being added to the polypeptide chain.
True or False?
Frameshift mutations have catastrophic effects on the resulting protein.
True.
Frameshift mutations are rare but generally have catastrophic effects on the resulting protein because the codon triplets are altered, potentially altering the sequence of amino acids and resulting polypeptide.
What is meant by the degenerate genetic code?
Degeneracy in the genetic code is where a single amino acid is coded for by multiple triplet codes.
What can cause gene mutation?
Gene mutations can be caused by mutagens and by errors in DNA replication or repair. Examples include chemical mutagens and mutagenic forms of radiation.
True or False?
There are specific regions of DNA where mutations only occur.
False.
Mutations can occur anywhere in the base sequences of a genome.
What are the natural mechanisms for making a deliberate change to a particular base with the purpose of changing a trait?
No natural mechanism is known for making a deliberate change to a particular base with the purpose of changing a trait.
What is variation in a species?
Variation refers to the differences that exist between organisms of the same species, such as coat color in mammals or flower color in plants.
What causes variation within a population?
Variation results from small differences in DNA base sequences between individual organisms within a population.
Name the three main sources of genetic variation.
Three main sources of genetic variation are mutation, meiosis, and random fertilisation during sexual reproduction.
What is the original source of genetic variation?
Mutation is the original source of genetic variation, leading to the generation of new alleles.
How do mutations contribute to evolution?
Mutations result in new alleles that can be advantageous, disadvantageous, or neutral, influencing natural selection and the evolution of a species.
Why are mutations important for evolution by natural selection?
Mutations introduce new alleles that can be selected for or against, contributing to the adaptation and evolution of species.
What is the only source of variation in asexually reproducing species?
Mutation is the only source of variation in asexually reproducing species.
What happens to a disadvantageous mutation in a population?
A disadvantageous mutation is less likely to be passed on because it decreases the organism's chances of survival and reproduction.
What are the two types of genetic testing available? (NOS)
Two types of genetic testing are clinical/medical genetic testing and commercial genetic testing.
Who typically performs clinical or medical genetic testing?
Healthcare providers such as doctors, nurse practitioners, or genetic counsellors perform clinical genetic testing.
True or False?
Commercial genetic testing always involves healthcare providers.
False.
Commercial genetic testing provides genetic tests directly to customers without necessarily involving healthcare providers.
What are some potential problems with commercial genetic testing?
Potential issues with commercial genetic testing include inaccurate results, stress from unexpected information, and the risk of making important decisions based on misunderstood information.
Why is genetic counselling important in genetic testing?
Genetic counseling ensures that individuals understand their test results and the implications for their health and family, reducing the risk of misinterpretation.