DNA Mutations Flashcards
Somatic Mutation
cell will be the progenitor of a population of identical daughter cells following division
-division of a cell with a new mutation will lead to a patch of cells with the new mutation
-the earlier the mutation occurs in the developmental stage the more the mutation will spread
-can’t be inherited
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Germline Mutations
cells that come together to produce new offspring in sexually reproducing organisms
- can be inherited
- every cell in the developing embryo will carry the mutation
Lederberg
- allowed bacteria to grow into colonies in a petri dish with age
- once they were growing the original plate was stamped onto a new cloth and then stamped onto a new plate that contained penicillin
- known as replica plating
- showed that only a few colonies survived indicated that some colonies contained mutations that made them resistant to penicillin even before they had been exposed to it
- proves that mutations are random and spontaneous
Mismatching Repair
- mismatching of a single nucleotide base pair can be correcting by DNA polymerase
- mismatched nucleotide creates a kink recognizable by proteins
- mismatch DNA backbone is cleaved by an enzyme (nuclease) some distance away from the mismatched region
- once the backbone is cut another enzyme is able to remove all the nucleotides from the cut DNA
- DNA polymerase and ligase can induce DNA synthesis to close the gap
Base Excision Repair
- incorporation of uracil in DNA that signals that DNA repair needs to be done
- DNA uracil glycosylase detects the uracil and can cleave the uracil from the backbone leaving behind the bare deoxyribose sugar
- lack of nitrogenous base is detected by AP endonuclease which cleaves the backbone on either side
- leaves an open gap that requires addition of new nucleotide
- DNA polymerase and ligase allow the addition of a new nucleotide
Nucleotide Excision Repair
- can remove and replace more than one damaged nucleotide bases
- damaged bases signal to specific enzymes to cleave the DNA backbone on either side of the damaged region
- DNA synthesis is able to completely fill the excised gap with the correct nucleotides
Point Mutations
can arise during replication
-most common type is a single nucleotide pair substitution where one base pair is incorrectly replaced by another pair of nucleotides (single nucleotide polymorphisms)
Missense Mutation
causes a single amino acid substitution
-can have bad effects
Silent Mutation
change in nucleotide sequence results in the same codon as before yielding no consequences
Nonsense Mutation
can change the codon for an amino acid into a stop codon
- cause translation to stop prematurely
- leads to non-functional proteins
Insertion
when one or more extra nucleotides are inserted into the replicated DNA
Deletion
skipping or removal of one or more nucleotides during replication
-cystic fibrosis is caused by a three nucleotide deletion
Frameshift Mutations
- whenever the number of nucleotides inserted or deleted is not in a multiple of 3
- leads to improper grouping of nucleotides
- leads to a massive missense mutation
- almost always leads to non-functional proteins
Chromosomal Duplications
- regions of the gene may be able to acquire small duplications during DNA replication
- can possibly lead to a new gene being formed
Chromosomal Deletions
- when a chromosomal fragment is lost
- can lead to loss of entire genes from that chromosome
- if centromere is lost the whole chromosome will be lost
