DNA Mutations Flashcards

1
Q

Somatic Mutation

A

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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2
Q

Germline Mutations

A

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
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3
Q

Lederberg

A
  • 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
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4
Q

Mismatching Repair

A
  • 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
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5
Q

Base Excision Repair

A
  • 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
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6
Q

Nucleotide Excision Repair

A
  • 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
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7
Q

Point Mutations

A

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)

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8
Q

Missense Mutation

A

causes a single amino acid substitution

-can have bad effects

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9
Q

Silent Mutation

A

change in nucleotide sequence results in the same codon as before yielding no consequences

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10
Q

Nonsense Mutation

A

can change the codon for an amino acid into a stop codon

  • cause translation to stop prematurely
  • leads to non-functional proteins
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11
Q

Insertion

A

when one or more extra nucleotides are inserted into the replicated DNA

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12
Q

Deletion

A

skipping or removal of one or more nucleotides during replication
-cystic fibrosis is caused by a three nucleotide deletion

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13
Q

Frameshift Mutations

A
  • 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
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14
Q

Chromosomal Duplications

A
  • regions of the gene may be able to acquire small duplications during DNA replication
  • can possibly lead to a new gene being formed
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15
Q

Chromosomal Deletions

A
  • 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
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16
Q

Chromosomal Inversions

A
  • normal order of a sequence of genes is reversed producing an inversion at that chromosomal region
  • occurs when a chromosome fragment breaks off and then reattaches to the same chromosome but in reverse order
  • don’t usually lead to serious consequences
17
Q

Reciprocal Translocations

A
  • occurs when a portion of one chromosome is able to attach to a non-homologous chromosome
  • two non-homologous chromosomes exchange terminal chromosomal fragments
  • often happen when a break occurs within the chromosome and the translocation is carried out before the break is repaired
  • tend to occur in noncoding regions of DNA so they don’t affect gene function
18
Q

Gene Evolution

A

-Beta-globin gene family consists of five different genes that all carry out the same function suggesting the gene evolved over time