T4M4 Flashcards
(22 cards)
Mutations can be created by
environmental factors, spontaneous mutations, errors during process of DNA replication
Why do RNA viruses have the highest probability of mutation?
delicate nature of the RNA backbone of RNA viruses and retroviruses (being more prone to damage and breakage), in addition to the fact that there is no proofreading capability in RNA genomes
Joshua and Esther Lederberg in 1952 showed that
mutations such as those of antibiotic resistance in bacteria are random and not directed
Mismatching of single nucleotide pairs during
DNA replication can be corrected by the
proofreading capabilities of
DNA polymerase
A mismatched nucleotide pair creates
a kink in the DNA molecule that is recognized by proteins that scan the DNA for damage and errors
Base excision repair
incorporation of a uracil in DNA that signals that
there is the need for DNA repair to be done
If any DNA molecules accidently incorporate a
uracil into their elongating strands
the presence of uracil is a signal that is detected by a DNA uracil glycosylase enzyme which will cleave the uracil from the sugar DNA backbone itself
DNA synthesis facilitated by
enzymes such as DNA polymerase and DNA ligase
Nucleotide excision repair
can remove and replace more than one
damaged nucleotide bases. It is the damaged
bases which signal to specific enzymes to cleave
the DNA backbone on either side or flanking the
region of damaged or mismatched bases
single nucleotide polymorphisms (SNPs)
Point mutation, a single nucleotide pair substitution where one base pair is incorrectly replaced by another pair of nucleotides
non-synonymous or missense mutation which causes a single amino acid substitution in the beta-globin protein subunits of the hemoglobin molecules that carry oxygen in our red blood cells causes what disease?
Sickle cell anemia
Insertion mutations occur when
One or more extra nucleotides are inserted into replicating DNA
Deletion mutations
involve the skipping, or sometimes removal of one or more nucleotides during DNA replication
Individuals that have a three-nucleotide deletion in their genes that code for the CFTR transporter develop
thick, sticky mucus as a result of the inability to transport chloride ions across their cells
Frameshift mutation
occur whenever the number of nucleotides inserted or deleted is not in a multiple of three
Chromosomal mutations
mutations that affect a larger region of the DNA and leads to visible changes in chromosomal structures that are distinguishable under the microscope
four major types of changes that can occur to
chromosome structure that can result in
chromosomal abnormalities
deletions, duplications, inversions and reciprocal translocations
Deletion can occur when a
chromosomal fragment is lost
duplication and divergence
Regions of a chromosome
may be able to acquire small duplications during DNA replication, don’t harm diploid organisms because the normal homologous chromosome provides a backup, extra copies due to mutations can be advantageous and lead to the formation of new genes with similar functions.
Inversion
a chromosome fragment breaks off and then reattaches to the same chromosome, but in the reverse order
Translocations
a portion of one chromosome is able to attach to a non-homologous chromosome
Reciprocal translocations tend to occur in
noncoding regions of DNA in larger genomes, so these types of mutations generally do not disrupt gene function
