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What is a gene mutation?
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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.
What is gene knockout?
Gene knockout is a technique that removes or makes a gene unusable in an organism in order to study its function.
What is a knockout organism?
A knockout organism is an organism that has had one or more of its genes knocked out or made unusable.
Define gene editing.
Gene editing is the process of altering the DNA of an organism by inserting, deleting or replacing DNA at specific sites in the genome.
How does gene editing differ from genetic engineering?
Gene editing differs from genetic engineering in that it involves modifying the existing DNA of an organism rather than inserting DNA from another organism.
Name an example of a medical condition that has been studied using gene knockout techniques.
Conditions that have been studied using gene knockout techniques include:
Obesity
Diabetes
Cancer likelihood
Addiction
Cardiovascular disease
What is CRISPR?
CRISPR is a gene editing technique that uses a bacterial defence mechanism to cut DNA at a specific point determined by a guide RNA.
What is the purpose of gene therapy?
The purpose of gene therapy is to treat genetic diseases by altering the person's genotype, or genetic makeup.
True or False?
The CRISPR-Cas system is used by prokaryotes for gene editing.
False.
The CRISPR-Cas system is used by prokaryotes as a natural defence mechanism, not for gene editing.
What is the role of ethics committees in genetic engineering? (NOS)
Ethics committees must approve all experiments involving genetic engineering and provide guidance on the ethical issues involved.
True or False?
Scientists across the world are subject to the same regulatory systems. (NOS)
False.
Scientists across the world are subject to different regulatory systems.
For this reason, there is an international effort to harmonize regulation of the application of genome editing technologies such as CRISPR.
Define the term conserved sequence?
A conserved sequence is a section of DNA or RNA that shows minimal mutations over time, often being identical or similar across a species or group of species.
What is a highly conserved sequence?
A highly conserved sequence is a sequence that shows little to no mutations over long periods of evolution.
Give examples of highly conserved sequences.
Examples of highly conserved sequences include those that lead to DNA replication, transcription, translation, and proteins involved in cellular respiration, such as DNA helicases, tRNA, ribosomes, cytochrome c, and ferredoxin.
What are two hypotheses for why conserved sequences exist?
One hypothesis is that conserved sequences exist within genes that code for proteins that are essential for an organism's survival, as mutations in these genes would lead to the cell ceasing to survive.
The other hypothesis is that certain sections of gene sequences are less prone to mutations and have slower mutation rates, due to more active DNA repair and proofreading mechanisms.
Define the term mutation rate?
Mutation rate is the measure of how many changes there are to the DNA sequence over time, either in a single gene or across the whole genome.
Why are coding regions of the genome more conserved?
Coding regions of the genome are more conserved because DNA repair and proofreading mechanisms are very active in these regions, correcting mutations more frequently.
Why are non-coding regions of the genome less conserved?
Non-coding regions of the genome are less conserved because error correcting and proofreading mechanisms are less active in these areas, allowing for higher rates of mutation.