Chapter 15: Mutations Flashcards
what is a mutation?
a change in the DNA sequence
what are the types of mutations?
point and frameshift
what is point mutation?
one nucleotide is changed to a different nucleotide
has the same number of nucleotides
what is frameshift mutation?
additional or deletion of at least one nucleotide
change the number of nucleotides
what are the types of point mutations?
silent, missense, nonsense
what are silent mutations?
the DNA sequence has been changed, but the new codon still codes for the same AA
a change in what base may not change the AA?
3rd base
what type of mutation?
one nucleotide has been changed to a different nucleotide
new codon codes for the same AA
silent
what type of mutation?
one nucleotide has been changed to a different nucleotide
new codon codes for the same AA
silent
what are missense mutations?
one nucleotide has been changed to a different nucleotide
new codon codes for a different AA
will silent mutations be functional?
yes- same function as before
will missense mutation be functional?
maybe, it would make a difference if it is in the active site and regulatory site
not make a huge difference when the AA is similar and it may work as a space holder
what is sickle cell anemia caused by?
point mutation in gene for hemoglobin=missense
what is nonsense mutation?
one nucleotide has been changed to a different nucleotide
new codon codes for a stop codon
new protein is shortened and missing some of its AA
will nonsense mutations be functional?
no, the protein is shortened
what type of mutation?
addition or deletion of at least one nucleotide
changes the number of nucleotides
frameshift
what are the types of frameshift mutations?
insertion and deletion
what is insertion frameshift?
additional of 1 or more nucleotides
what is deletion frameshift?
removal of one or more nucleotides
will frameshift mutations be functional?
no, many AA are changed because all codons are shifted over
where can mutations occur?
germ-line or somatic cells
what can mutations be?
harmful: cause changes in protein sequence or gene expression that leads to health problems
nuetral: no effect
beneficial: can have beneficial effect on health
mutations are the source of
new alleles
what are somatic cells?
body cell (not reproductive)
what are germ-line cells?
reproductive cell that makes the sperm or eggs (gametes) testes or ovaries
what happens if gametes have mutations?
all cells in embryo will have mutation
all cells in organism will have 1 copy of the mutation
humans are diploid so 2N =
Gametes are haploid so 1N =
2 copies of each chromosome
1 copy of each chromosome
how many gametes will have the mutation?
half
what happens if somatic cells have mutations?
everytime the cell divides the daughter cells will inherit the mutation/ produce a patch of cells with the mutation
what cells mutations will not be inherited and why?
somatic
none of the cells that produce the sperm or eggs have the mutation
what causes mutations?
spontaneous and induced
what are spontaneous mutations caused by?
types
caused by mistakes in cellular processes or metabolism
errors during DNA replication
toxic metabolic products
changes in nucleotide structures
transposons
what is errors during DNA replication
proofreading does not remove all mismatched bases
DNA repair enzymes fail to remove all mistakes/ DNA damage
what is toxic metabolic products?
metabolism produces relactive chemicals that change structures of bases in DNA
when does toxic metabolic products occur?
after the DNA replication is done so the next time it is replicated there is a mistake
what is changes in nucleotide structure?
bases can form isomers/ alternate forms = tautomers
can cause misprinting during DNA replication
what is a tautomer?
alternate form of base
each base can change between what two forms?
standard form and tautomer ( alternative form)
If the base is in the ___ form during DNA replication the ____ base can be inserted into the DNA = ____ mutation
alternate
wrong
spontaneous
what are transposons?
jumping genes
1000 bases long
if a transposing inserts into a gene it will cause a mutation
what type of mutation is transposons?
insertion frameshift
when the transposon goes into the coding region it will form a really long mRNA and will be nonfunctional
what are induced mutations caused by?
environmental agents
- chemicals
- physical agents: uv light, x-rays
what is adenine?
an abnormal base in DNA
what is induced mutations?
chemicals change the structure of bases in DNA
what does uv light produce?
thymine dimers
what is a thymine dimer?
2 thymines on the same strand of DNA form covalent bond
during DNA replication thymine dimer is recognized as
what is added/produced
1 abnormal base not 2 Ts
mismatched base may be added
a deletion may be produced
what is the process of thymine dimers?
uv light causes thymine dimer
crosslinks 2 thymines on same strand of DNA
blocks DNA replication
thymine dimers cause
mistakes during DNA replication
what are the types of DNA repair systems?
mismatch repair
nucleotide excision repair (NER)
what is mismatch repair?
removes mismatched bases that are present after DNA replication is completed
what is nucleotide excision repair?
removes abnormal bases (u, hypoxanthine) and thymine dimers
in nucleotide excision repair, the ___ and ___ proteins form a ___ and move along the DNA looking for ____ bases
UvrA and UrvB
complex
abnormal
how does mismatch repair work in relation to nucleotide excision repair?
the same just with different proteins
what are the steps for nucleotide excision repair?
1) the UrvA and UrvB proteins form a complex and move along the DNA looking for abnormal bases
2)the UrvA and UrvB bind to region of DNA surrounding the abnormal base=thymine dimer
3) UrvA is released
4) UrvC binds to UrvB and cuts out a region of DNA surrounding the abnormal base= thymine dimer
5) UrvD unwinds DNA and removes cut piece of DNA
6) DNA polymerase 1 fills in gap with DNA
7) DNA ligase connects pieces of DNA together
what is xeroderma pigmentioa?
symptoms/ results
disease caused by defect in DNA repair enzymes that remove thymine dimers
patients blister or freckle when exposed to sunlight
develop precancerous lesions
skin cancer
can’t go out in sun even with sunscreen
what is myostatin?
inhibits growth of muscle cells
mutation that inactivates myostatin causes
overproduction of muscle cells
what is the bully mutation and how is it occurring
myostatin
naturally
