Mutation - 4 Flashcards
What 4 nucleotides is the sugar phosphate made up of
2 pyrimidines (cytosine and thymine)
2 purines (adenine and guanine)
What are the 6 possible changes that can occur in DNA substitution mutations
2 transitions and 4 transversions
Define transitions (ts)
substitution mutation with the same shape change, purine to purine or pyrimidine to pyrimidine
Define transversions (tv)
mutation with a different shape change, purine to pyrimidine or vise versa
Do we see transitions or transversions more and why
more transitions because they go from similar size and structure whereas transversions result in larger changes and cause much more disruption to DNA therefore either won’t happen or will be more noticeable and repaired quicker.
Define point mutation
a change in a single nucleotide that results from random error during DNA synthesis or repair
What are the two types of point mutation events
insertions and deletions
Define wobble codon
an example of a natural mutation where T-G or C-A occasionally bind, but doesn’t affect its function.
what are the 3 types of affects that result if a mutation occurs in the coding region
synonymous, nonsynonymous or nonsense mutation
Define synonymous mutation
SILENT
the mutated amino acid is not modified
Define nonsynonymous mutation
MISSENSE
mutation that changes the amino acid and may alter the function of a protein
Define nonsense mutation
mutation that introduces a premature stop codon which often makes the protein nonfunctional.
_____ mutations are more common than ____ mutations because of what two reasons
synonymous, nonsynonymous
1. nonsynonymous mutations are subject to higher selective pressures as they cause a disadvantage to organisms
2. transitions are more likely to cause synonymous mutations which is less likely to be repaired in mechanisms making them more common
Define transposons/jumping genes
elements of the DNA that can move from one location to another within a genome
Ex. in kernel colour, there is a gene that can cause another gene to “jump” within the genome and can cause colour inhibition
What are the two types of duplicated genes
paralogous and orthologous
Define paralogous genes
genes that are similar due to duplication
Define orthologous genes
similarity due to ancestry
genes in different organisms that are inherited by speciation instead of the same organisms
Define exon and intron of globular genes
introns = noncoding stretch of DNA that occurs between coding regions that must be spliced out to produce functional mRNA
exons = nucleotide sequence that occurs between introns and remain in the mRNA.
What are the 3 “fates” of duplicated genes
- rRNA = still retain original function
- globin genes = obtain a new function
- pseudogene = become functionless
What are the four types of chromosomal alterations
- insertions/deletions
- translocations
- inversions (flipped in reverse order)
- polyploidy
What does chromosomal rearrangements cause an increase of in ecosystems
variation!
Define polyploidy
organisms with more than two chromosomes per set
how does polyploidy cause instant speciation
mistakenly creates a tetraploid instead of diploid and they can no longer reproduce with the diploids meaning they created a new species. tetraploids must now reproduce with tetraploids
What are 3 reasons why mutations are not always bad
- high mutation rates can be advantageous to form new habitats and in unstable environments
- not all mutations are harmful
- when new mutations occur, selection will likely act on them and create a smaller fitness difference within species
Explain the balance between selection and mutation
most mutations are slightly deleterious until selection comes along. selection is necessary to select for or against or else mutation would quickly accumulate. but mutations are also still required for evolution!
