Mutations and Natural Selection Flashcards
Mutations to DNA are a source of new ____
Gene alleles
Mutations are made by _____ , _____ and/or ____
of bases in the DNA sequence
Mutations are made by insertions, subsitutions and/or deletion of bases in the DNA sequence
Point mutations can be ____ , _____ or _____
Mutations can be silent, missense or nonsense mutations.
Silent mutations are -
Mutations which cause no change to the function of the protein
Missense mutations are -
Mutations which cause a mild or serious change to the function of the protein, depending on the location of the mutation
Nonsense mutations are
Mutations which cause transcription of the protein to finish early, creating a protein which is too short to function.
What might mutations in the regulatory regions of a gene cause?
Mutations in regulatory regions of the gene may alter the rate of gene expression.
Where might a mutation occur that can be passed on to offspring?
In the germ line cells
Splice -site mutations are?
Point mutations that occur at splice sites
Mutations of regulatory sequences occur ___
Point mutations that occur at the enhancer region of a eukaryotic gene or the operator region of a prokaryotic gene
Natural selection acts on an organisms ___
Phenotype
If a new heritable mutant allele specifically confers a survival/reproductive advantage in a given environment . . .
Organisms carrying this new allele will survive longer and produce more offspring, proliferating the spread of the new allele. (The alleles frequency will increase generation by generation)
The 3 types of natural selection are
Diversifying
Directional
Stabilising
Give an example of directional natural selection
An example of directional selection is giraffe neck lengths. The environment created a selection pressure which favored giraffes with longer necks who could reach more food in the trees. At the same time, there was selection pressure against giraffes with shorter necks. Over time, the long neck phenotype dominated due to selection pressure, i.e., this trait in giraffes shifted toward the direction of long necks.
Give an example of stabilising natural selection
The birth weight of human babies stays within a certain range because babies that have a very low birth weight have less chance of survival and those with a very high birth weight can cause complications during delivery which threaten the life of the mother and the child.
