D1.3 Mutations in genes Flashcards
Function of non-coding sequences in genes (4)
regulators of gene expression
introns : found in eukaryotes, removed after transcription
telomeres : found at ends of chromosomes to ensure correct replication
genes for tRNA and rRNA
Define a mutagen
chemical or physical agent which can cause a mutation
Define a mutation (2)
changes to genetic composition of cell
change in order of bases in DNA strand
2 regions of pre-mRNA (2)
exons : protein coding regions
introns : non-protein coding regions
region of mRNA
exons : protein regions
Define post-transcriptional modification (2)
process where mRNA which is produced needs to be modified before translation
introns are removed using spliceosomes
Define spliceosomes
large enzymes found in nucleus
Define spontaneous mutation
mistake made when DNA is copied during production of gametes
3 Different types of mutation (3)
Substitution
Insertion
Deletion
Features of single nucleotide polymorphisms (2)
occur when one nucleotide is replaced by another nucleotide in DNA sequence
effect on protein structure depends on whether substitution is synonymous or non-synonymous
Define synonymous SNPs (3)
known as neutral/same-sense mutations
change one codon of amino acid into another codon of same amino acid
do not affect phenotype
Define non-synonymous SNPs (3)
change in amino acid sequence causes change in protein function
non-sense - changes codon into stop codon, polypeptide is not complete + resulting protein does not function properly
mis-sense = change codon into codon coding for different amino acid
Causes of frameshift mutations (3)
insertion
deletion
duplication
Impacts of frameshift mutations (3)
alters amino acid sequence coded by DNA sequence
addition of new nucleotides alters grouping of codons
mRNA transcript produced will have different codon structures
Define insertion for gene mutation
one or more nucleotides added to DNA sequence
Define deletion for gene mutation
one or more nucleotides are removed from DNA sequence
Examples of chemical mutagens (3)
mustard gas
nitrous acid
Formaldehyde
Example of physical agent mutagens (3)
UV Radiation
X-Ray
Gamma rays
Impact of radiation on gene structure (3)
single-strand breaks - interrupts continuity of template strand –> replication errors
double strand breaks
chemical alterations to bases
Base with highest probability of mutation (3)
cytosine
can experience chemical reaction called deamination
can lose an amine group –> becomes uracil
Factors that influence mutation rate (3)
exposure to mutagens
DNA repair mechanisms
fidelity of DNA replication - accuracy of DNA copy
Where can gene mutations occur (2)
somatic cells - all cells in body except germ cells
germ cells - cells that give rise to eggs + sperms
Mutations in somatic cells (2)
can cause diseases in person’s lifetime (e.g cancer)
not passed onto offspring
Mutations in germ cells (2)
passed onto offspring - mutations inherited by offspring
can cause genetic disorders, change chromosome number, increase susceptibility to certain disease
Define neutral/silent mutations (3)
mutations which do not significantly affect organism
neutral mutations - occur in non-coding regions of genome + regions that do not alter function of essential genes
silent mutations - occur in coding regions but do not alter amino acid sequence due to degeneracy
Define harmful mutations (2)
mutations that cause negative consequences for organism
can cause disease, abnormality, reduce organisms survival
Define beneficial mutations (2)
mutations that are advantageous to organism
improve ability to adapt, reproductive success, resistance to disease
Define genetic engineering (2)
process of altering DNA of organisms
to introduce new characteristics, modify characterstics, remove undesired characteristics
Define gene knockout technique (2)
specific gene is intentionally removed/changed to prevent its expression
helps to discover function of specific gene
Gene knockout technique in mice (4)
prepared DNA inserted into genome of embryotic mouse cells –> replaces + deletes target gene
succesful procedures grown into adult mice
males + females with only one copy mated - 25% expected to have no copies of target gene (knockout mice)
phenotype of knockout mice investigated to find out traits changed
Components of CRISPR-Cas 9 (2)
enzyme Cas9 - cuts DNA at specific target sites on chromosome
CRISPR
Define CRISPR (2)
short repeated base sequences
unique spacer sequences
Define the CRISPR Cas-9 system for bacteria (3)
used by bacteria against invading foreign DNA (viruses)
incorporate short segments of foreign DNA into their own genome
bacteria create molecular record of previous infections
Explain the CRISPR Cas-9 procedure for bacteria (4)
foreign DNA matches
foreign DNA matches CRISPR spacer –> corresponding RNA identifies + binds to specific viral sequences
guides Cas9 to target DNA to make precise cuts in DNA
causes double stranded break that can be repaired by cell’s DNA repair mechanism
CRISPR Cas-9 in gene editing (4)
creating single guide RNAs (sgRNA) to target specific genes for modification or deletion
sgRNA molecule specifically targets + bind to a particular DNA sequence of interest
guides Cas9 enzyme to location and enables it to make precise cuts in the DNA, resulting in double-strand break.
scientists can add, delete or modify the DNA sequences at that point
Application of CRISPR Cas-9 system (4)
gene therapy
agriculture
disease modelling
genetic engineering of microorganisms
Gene therapy in CRISPR Cas-9 system (3)
treats genetic disorders
correcting disease-causing mutations in a patient’s cells
e.g sickle cell anaemia.
Agriculture in CRISPR Cas-9 system (3)
ability to transform crop breeding practices
introducing precise genetic modifications to enhance desirable traits
improve crop yield + nutritional content and disease resistance
Disease modelling in CRISPR Cas-9 system (3)
creates animal models to simulate human diseases
introduces mutations or deleting genes in animals
researchers gain info into disease progression + potential treatment
Genetic engineering of microorganisms (3)
make modifications to genetic material of bacteria, yeast or other microorganisms.
enhance microorganisms’ ability to produce valuable compounds such as pharmaceuticals, biofuels and enzymes.
creation of efficient microbial factories to contribute to sustainable production
Define conserved sequences
sequences remain identical or similar across species or group of species
Define highly conserved sequences
sequences that remain similar over long periods of evolution
Role of conserved and highly conserved sequences (2)
provide clues about function/importance sequences for evolution of species
functional constraints - selective pressures prevent mutations in these genes as they are vital for life
