D1.3 Mutation Flashcards
(21 cards)
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.
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.
What are the three forms of substitution mutations?
The three forms of substitution mutations are silent mutations, missense mutations, and nonsense mutations.
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.
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.
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.
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.
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.
