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LIFESCI 2G03 Test 1 questions and answers complete solution 100% 2024/2025
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LIFESCI 2G03 Test 1mutation
a change in the DNA sequence
germline mutation
heritable, occurs in germ-line cells, and is passed on/present in all cells of the progeny
somatic mutation
non heritable, does not occur in germ-line cells, is not passed onto progeny, is passed
onto all descendants of that cell
what regions of the DNA are affected by germline and somatic mutations, respectively?
both types of mutations may affect the protein coding regions or the non-coding regions
what is the effect of mutations in protein coding regions?
affects the polypeptide sequence, and may impact protein function
what is the effect of mutations in non-coding regions?
in non-coding RNA: impacts gene expression
in introns: impacts polypeptide sequence
wildtype allele
the more abundant allele
mutant allele
the more rare allele
loss of function mutation + the 2 types
reduces or abolishes protein function.
1. null (amorphic): complete loss of protein function
2. hypomorphic: incomplete, reduced activity
gain of function mutation + the 3 types
increased activity or new function; or expression in the wrong place/time
1. hypermorphic: more protein or increased activity
2. neomorphic: generates a new function
3.dominant negative/anti-morphic: prevents the normal protein from performing its
homeostatic function
are loss-of-function and gain-of-function mutations usually dominant or recessive?
-loss of function: can be either
-gain of function: almost always dominant
Tp53
transcription factor that acts as the gatekeeper of cell cycle progression; stopping the
cell cycle if there is DNA damage; tumor suppressor
what is Tp53 supposed to do when there is damaged DNA?
promote apoptosis genes, promote DNA repair genes, and inhibit cell cycle genes
DBD + function
the DNA binding domain, important for Tp53 to bind to DNA and regulate transcription
What happens when there is a loss of function of DBD?
, reduction in DNA binding capacity, abolished gene expression, increased proliferation of
mutated cells
what type of mutation causes a mutant p53 protein?
dominant negative/anti-morphic mutation
what happens when there is a mutant p53 protein?
-suppresses the function of wild type p53
-does the opposite of what's supposed to happen: inhibits apoptosis genes, inhibits
DNA repair genes, and promotes cell cycle genes
spontaneous mutation
occurs randomly with no known cause
induced mutation
arises due to exposure to mutagenic agents and radiation
what happens more often, spontaneous or induced mutations?
induced
point mutation + types
change in a single nucleotide, or a few base pairs. types: substitution, deletion, insertion
chromosomal rearrangement
large deletions, insertions, inversions, or translocations. at the chromosomal level,
sometimes deletions and insertions happen together
aneuploidy
changes in chromosome number
3 types of point mutations
1. nonsense
2. missense
3. silent
nonsense mutation
codes for a stop codon
missense mutation
codes for a different amino acid, resulting in a nonfunctional protein, or a protein with a
different function
silent mutation
code for the same or different amino acid, but there is no functional change in the
protein
what is tautomeric shift?
the sudden change to a tautomer, a transient isomeric form of a nitrogenous base
how do point mutations happen?
tautomeric shift
what is hemoglobin?
a tetramer formed by two a-globin and two b-globin subunits, that carries oxygen
throughout the body
what happens when the HBB gene undergoes a point mutation?
A becomes T (RNA), which translates to U. glutamic acid becomes valine at position 6.
this causes sickle cell disease
What are the 2 types of indels (frameshift mutations)
insertion and deletion
how do small indels happen?
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