Changes in genetic makeup of a population Flashcards
U4AOS1
Allele
Variation of a gene
gene pool
should be called allelle pool. Complete set of alleles present in a population.
polyploidy
Condition in which an organism has more than two matched sets of chromosomes.
eg: triploids, tetraploid, etc.
Allopolyploid
When the additional chromosome sets in a polyploid comes from antoher speices.
Autopolyploid
Additional chromosomes sets in a polyploid are from its own speices.
Aneuploidy
When an organism has a chromosome number that differes by a small number from the standard chromosome number for its speices.
typically +/- 1 or 2.
Point mutations
Affect a single base in DNA, either by substitution, insertion, or deletion.
Base substitutions
mutations can be can be silent, nonsense, or missense
Silent mutations
The substitution does not change the polypeptide produced. One amino acid may be coded for by a variety of codons.
Can only be identified when DNA is examined.
Nonsense Mutations
-sub may result in STOP codon, therefore shorten polypeptide chain.
this would result in missing amino acids, and therefore different protein folding
more detremental than missense (just diff folding)
Missense Mutations: conservative mutations
-conservative: sub still enables mutation to be tolerated. EG: the diff amino acid may have similar chemical properties (eg both hydrophobic)
Missense Mutations: non-conservative mutations
-non-conservative: sub results in sub of amino acid with diff chem properties, that connot be tolerated.
Point Mutations: Frameshift mutations
insertions or deletions that cause the remaining bases to SHIFT (to the left/right.).
Missense vs Nonsense
mis= replacement of amino acid, nonsense= stop codon
Points for natural selection to occur:
- There is a variation in population
- a selection presuure means that some organisms have a better chance of reproducing than others.
- the organism that reproduce are likely to pass on favourable characteristics (alelles) to the next generation
- greater (allele) frequency of favoured characteristic is present in population.
natural selection
gene flow
movement of alleles between populations by migration/emigration of individuals carrying them.
-there MUST be sexual reproduction for new alleles to be introduced into the population. This introduction is the “gene flow’
genetic drift
- changes in allele frequencies that occur by chance
- bottleneck, founders effect
- not driven by selection pressure
Genetic drift: bottleneck
- allele frequencies of survivors are unrepresentative of the original population. (the population must start again)
- 12 blue:8 red. a fire comes along. now it’s a 1 blue: 6 red ratio.
genetic drift: founders effect
- allele frequencies of founders have different allele frequencies than the original population. (involves moving and starting a new population)
- og pop has 12 blue: 8 red. dude comes along and takes a sample, the sample has a 1 blue: 6 red ratio.
how can allele frequencies be cha nged?
selection, gene flow, genetic drift
How do new alleles appear?
gene flow, mutation
HOw is a subspecies formed?
One of the population becomes serveral seperate population, and each undergoes changes in isolation from the other populations.
they are considered to be part of the same species if they’re still able to produce viable, fertile offspring when the both do the diddly doo.
allopatric speciation
speciation caused by geogrphical isolation.
