d1.3 (mutations & gene editing) Flashcards
in which direction does DNA polymerase synthesize?
5′ to 3′ direction
types of gene mutations x3
substitutions
insertions
deletions
what does gene GNAT2 control for? where is it found? how does it occur?
protein product named “transducing”, a protein required for colour vision
it is found on chromosome 1 complementary strand
single base pair substitutions
“Other times, substitution in DNA occurs and changes the amino acid that is translated from the RNA sequence generated.”
two examples & definitions of a substitution
Missense: single base pair mutation that changes the amino acid. If amino acid is similar to what it should me, functionally the protein can still work (perhaps not as well).
Nonsense: a single base pair mutation that changes codon to a stop codon. Results in incomplete primary sequence. Protein typically not functional (though depends on where in the sequence it occurs).
2 characteristics of glutamic acid (amino acid prior to sickle cell disease)
polar
mRNA = GAA
2 characteristics of valine (amino acid after to sickle cell disease)
non-polar
mRNA = GUA
if both copies of sickle cell gene are mutated, what occurs?
sickle cell disease
if only one copy of sickle cell gene is mutated, what occurs?
malaria resistance
how is malaria dangerous? how does sickle cell disease work against this?
attack red blood cells & causes fever symptoms
with sickle cell disease, your cells are too small and limits malaria’s asexual lifecycle
what causes huntington’s disease? on what chromosome is it located
CAG sequence normally repeats 10-35 times. in those with Huntington’s disease, it is repeated 36-120 times or more (gene HTT)
expanded sequence leads to the production of an way longer version of the HUNTINGTIN (yes spelt this way) protein, which then accumulates in brain cells and causes damage
occurs on chromosome 4
CCR5-Δ 32 involves deletion of what? what does it result in?
32 base pairs in the CCR5 gene
as this is not divisible by 3, results in frameshift
deletion results in a nonfunctional CCR5 receptor, which means the receptor is either not produced or is not expressed correctly on the cell surface
CCR5-Δ 32 immunity and vulnerability to a certain disease (1 each)
beneficial protection against HIV
makes people more susceptible to West Nile Virus
main causations of mutations x3
physical mutagens
chemical mutagens
DNA replication
example of chemical mutagen. what is it used for?
Benzene: carcinogenic. Used to make acetone, polystyrene, and nylon fibres.
how can ionizing radiation (x-rays and gamma rays) create mutations? x2
radiation with sufficient energy can knock one of more base pairs out of place.
ionizing radiation has enough energy to break a covalent bond, and enough to break an H bond.
examples of damages to DNA from radiation (name a few)
H bon breakage
double strand break
single strand break
base losses
base changes
dna cross linkage
protein cross linkage
pyrimadine dimer
look at slide 19 for a visual on proofreading
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in what region is mutation rates higher? why?
satellite DNA near the centromere, because it is the site where sister chromatids bind
mutations can also occur where? x2
mutations can also occur when? x1
in mitochondrial DNA, in RNA genomes
in transcription of RNA
define CpG site
any place where a cytosine is followed by a guanine
what is the methylation of cytosine?
sometimes causes cytosine to deaminated to thymine (look at slide 24 for visual)
define CpG islands
places with many CpG sites. higher chance of mutation
are we sure of what methylation does? what can it perform?
not sure what methylation does, in some places it regulates gene expression but hypermethylation often seen in cancers.
what is methylation essential for?
cell differentiation and embryonic development
