Ch. 12 Flashcards
Mutation
change in DNA sequence is rare in a population and typically affects the phenotype
“loss of function” mutations - recessive
“gain of function” mutations - dominant
SNP vs. Mutation
Mutations are like rare typos in your DNA book that can sometimes cause problems or changes.
SNPs are like common tiny changes that lots of people have, and most of the time, they don’t cause problems.
Polymorphism
gene variant (allele) present in more than 1% of a population
Gene variant
refers to both polymorphisms and mutations
Mutant
refers to phenotype and describes an allele
Gremline Mutation
change occurs during the DNA replication that precedes meiosis
transmitted to the next generation of individuals
Somatic Mutation
happens during DNA replication before a mitotic cell division
affect only cells that descend from changed cellS
Somatic Mosaicism
a person with somatic mutation
when somatic cells mutate in an individual, not all cells in individual have that mutation
Spontaneous Mutations
errors in normal cellular processes such as DNA replication, can be caused by natural changes in the molecular structure of the bases in DNA (chemical instability
de novo (new mutations)
Induced Mutations
caused by mutagens or carcinogens, such as radiation and chemicals, that affect DNA and cellular processes
Radon
naturally occuring radioactive gas that can cause lung cancer, second leading cause of lung cancer in US
Conversion of Cytosine to Uracil by nitrous acid (hno2)
nitrates and nitriles used in preservation of meat are converted into nitrous acid in the body
Silent Mutation
changes a single nucleotide in the DNA sequence but does not alter the amino acid sequence of the resulting protein.
Missense Mutation
occurs when the change in nucleotide results in subtitling one amino acid for another in the final protein
Nonsense Mutation
occur when the change in results in submitting a stop codon for an amino acid in the final protein
Frameshift mutation (1 bp deletion)
when nucleotides are inserted or deleted from genome. shifts the reading grade usually and results in premature truncation of the protein ; can be insertion or deletion mutations
Splice Site Mutations
alters a site where an intron is normally removed from mRNA
can affect phenotype if:
- intron is translated into amino acids
- exon is skipped (exon skipping)
Deletion
removes genetic material
Insertion
adds genetic material
Tandem Duplication
two complete copies of a gene next to each other
Pseudogenes
DNA sequence similar to a gene but not translated, may be transcribed into mRNA
gene sequence duplicated when DNA strands misaligned during meiosis
Transposons
“jumping genes”
DNA polymerase can make mistakes during DNA replication, but at a very low rate; proofreading mechanisms also help prevent mutations
Transposons can insert and remove themselves from the genome; if insert code in middle of sequence mutation can disrupt the gene
Expanding repeats
gene grows as small part of DNA sequence is copied and inserted
more repeats = more severe
Anticipation
expansion of triplet repeat with an increase in severity of phenotype with subsequent generations
<40 repeats = not associated w. symptoms, but larger repeats = unstable
A __ is a change in a DNA sequence that can cause varying effects.
mutation
The term ___ is increasingly being used to mean both polymorphism and mutation.
variant
A mutation that occurs during the DNA replication preceding meiosis is called a
germline mutation
A mutation that occurs during the DNA replication preceding a mitotic cell division is called a
somatic mutation
A ___ mutation will be present in some of the cells in an individual’s body but will be absent from other cells.
somatic
You have performed exome sequencing and have identified a gene in which two different mutant forms are prevalent. Each mutation is a missense mutation, but they are found in different parts of the gene.
What can you conclude about these mutations?
They may each cause a different disease.
When a gene is disrupted by a DNA sequence “jumping” into it and disrupting the reading frame, the DNA sequence that jumps into the gene is called a
transposon
A mutation that can be passed on to all the cells in a person’s progeny is a _________ mutation.
germline
In sickle cell disease, a _________blank that is normally in the beta globin polypeptide is replaced with a _________blank.
glutamic acid; valine
Exposure to radioactive substances in the Earth’s crust is an example of
natural exposure to mutagens
Consider the following gene:
Exon H - Intron 1 - Exon I - Intron 2 - Exon J - Intron 3 - Exon K - Intron 4 - Exon L.
The gene undergoes 2 splice-site mutations, one causes Intron 4 to be retained, and another that causes skipping of Exon K.
Select the correct structure of the translated protein.
H-I-J-4-L
A tautomer is
an alternate structure of a molecule.
DNA Repair Mechanisms
Double-strnaded break repair
ionizing radiation oxidative damage
DNA Repair Mechanisms
Excision repair: nucleotide excision repair or base excision repair
UV exposure
DNA Repair Mechanisms
Damage tolerance
small errors ignored
DNA Repair Mechanisms
Mismatch Repair
Replication errors
