Mutations (2/23) Flashcards
What are the two sources of variation within a species?
- ) Mutation
2. ) Recombination (occurs during sexual reproduction)
What has a higher rate of point mutations, bacteria or higher eukaryotes?
Bacteria!
What are Types of “Point Mutations” Within a DNA Sequence?
a. ) Substitution: switches the sequence in only one spot
b. ) Insertion: moves the whole line of codons down a letter
c. ) Deletion: moves the whole line of codons back one letter
Is evolution a random process?
No! Mutations happen at random but natural selection is the filter!
Synonymous Codons
mutations that do NOT change the meaning of a triplet
Non-Synonymous Codons
mutations that result in the replacement of one amino-acid for another
What is the ratio of Synonymous Codons and Non-Synonymous Codons found in nature?
It is expected to be 3:1, but in nature it is actually 1:3 because natural selection purges non-synonymous mutations that alter the amino acid sequence of a protein while it is more permissive of synonymous mutations
What are “Pseudogenes”?
“Use it or Lose it”; fossil genes that no longer serve a function
- they arise because certain genes become useless as organism evolve, but those genes still remain conserved within the genome
Mutagenic Chemical Agents
exposure to mutagenic agents may cause mutations (UV Radiation, Tobacco Smoke, etc.)
Recombination as a Source of Variation
sexual reproduction increases the variability in a population;
- permits a wider range of evolutionary response
- permits a more rapid evolutionary response
- offspring bear a new combination of alleles
Crossover Between Chromosomes During Meois
partial exchange of genetic information between two homologous chromosomes can reshuffle allele combinations