Mutations Flashcards
what are mutations?
a mutation is a change in the nucleotide sequence of a genome.
what are the two types of mutations?
small scale mutations and large scale mutations
what are the consequences of mutation?
beneficial, neutral, harmful
whether a mutation is beneficial, harmful, or neutral, depends on?
it is determined by the environmental conditions that are present at the time.
what are the two ways mutations can occur?
spontaneous mutations and induced mutations
what are spontaneous mutation?
the spontaneous mutations arise occasionally in all cells in the absence of any added agent.
- may be caused by errors during dna replication
what are induced mutations?
induced mutations arise due to exposure to a mutagen.
- a mutagen can be physical or chemical agent.
examples of physical agent?
uv radiation from the sun: can induce mutations by damaging the bases. this causes incorrect base pairing during replication resulting in mutations.
what is an example of a chemical agent?
ethidium bromide: it is used to visual dna.
- it works by inserting itself between the bases so when dna replication occurs, it causes a single nucleotide insertion or deletion.
what are the two types of small scale mutations?
- nucleotide pair substitutions
- insertions or deletions
what is nucleotide pair substitution?
replacement of one nucleotide and its partner with another pair of nucleotides
the substitutions can be?
silent, missense, nonsense
what is a silent mutation?
occurs when a nucleotide is changed in dna but does not cause a change in the amino acid
what is a missense mutation?
this is when the nucleotide change in dna also does change the amino acid sequence
- it may or may not have an affect on the function of the protein
sometimes however, a nucleotide pair substitution can have a major change in the protein?
sickle cell disease: The glutamic acid is replaced with valine. This results in the hemoglobin having a mutation.
what are some symptoms of sickle cell disease?
- fatigue
- anemia
- swelling of hands and feet
- bacterial infections
- leg ulcers
- lung and heart injury
- pooling of blood in the spleen and liver congestion
what is a nonsense mutation?
a nonsense mutation is one that results in the formation of a stop codon. the result is premature termination of a polypeptide.
- nonfunctional protein
what are insertions or deletions
insertions and deletions are the second type of small scale mutations
- occurs when one or two base pairs are added or deleted.
- less than 3 results in shift in the reading frame and called a frameshift mutation.
what are long scale mutations?
long scale mutations are chromosomal rearrangements that affect long segments of dna.
what are the two ways long scale mutations can occur?
errors that occur during meiosis or exposure of dna to damaging agents
long scale mutations can cause?
a change in the chromosome structure or change in chromosome number
what are the 4 types of changes in chromosome structure?
deletions, duplications, inversions, translocations
what are deletions in long scale mutation: change in chromosomal structure ?
chromosomal fragment is lost: result in missing genes
what is duplication?
a chromosomal fragment that has broken off that may join a homologous pair.
deletions and duplications usually arise due to errors that occur?
in meiosis in prophase i
what is inversion?
a chromsomal fragment after breakage reattaches to the original chromosome but in reverse orientation
what is translocation?
the chromosomal fragment after breakage may join a nonhomologous chromosome
consequences of chromosomal rearrangements?
- generally harmful
- large deletions can be lethal
changes in chromosome number can arise from?
a mistake made during meiosis called nondisjunction: the failure of a pair of homologous chromosome to separate.
- this results in two gametes having an extra copy of the chromosome and two gametes not having the copy if in meiosis i but in meiosis ii, 2 are normal.
what happens next?
if the abnormal gametes fertilize with normal gamete, the zygote will have an abnormal number of chromosomes.
- aneuploidy
an example of an aneuploid condition?
downs syndrome: extra copy of chromosome 21: trisomy 21.
most cases of downs syndrome arise from?
nondisjunction during meiosis i
some organisms have more than two complete chromosomal sets, what are these called?
polyploid
