4B - Diversity and selection Flashcards
diploid and haploid
diploid = 2n, haploid = n
fertilisation = random , porduces zygotes with diff combination of chromo to both parents - inc genetic diversity within sp
Meiosis
- the DNA unravels and replicates
- the DNA shortens and condenses to form double arms - 2 sister chromatids, joined together by centromers
- the hommologus pair arrange themselves against each other
- Meiosis l = homologous pair seperate
- Meiosis ll = sister chromotids sepe
produce 4 genetically diff daughter cells
creating genetic varitation in gametes
- crossing over of chromatids
- independent segration
crossing over
when homologous pair line up against each, sister chromatids can twrist around eachother
- chromatids = still contains the same genes but now have diffrent combo of alleles
independent segregation
- when homo pair sepe , completdely random which chromo from each pair ends up in which daughter cell
- 4 daughter cell = complety diff combo to those of mother and father
potcomes of mitosis and meiosis
- mitosis - 2 daughter cells, gen identical, same number of chromo as parent cell
- meiosis - 4 daughter cell, gen diff, half the number of chromosome as parent cell
Gene mutation
- change in base seq - change in AA - change in poly - change in tertiry stu
- sub - swap bases
- deletion - dele bases, changes mumber of base present , cause shift in base triplets after it
why sub sometimes codes for the same AA
due to the degenerate nature of genetic codes
- diff base seq codes for the same AA
chromosome mutation
- mutation of chromosomes = inherited conditions - errors present in gametes
- one of mutation = chromosome non disjuction
- chromosome not divide properly
genetic diversity
number of diff alleles within the sp or population
- larrge number of diff alleles, large variety of different characteristics
why genetic diversity important
- if the population has low geentic diversity , might not be able adapt to change in envi
- ansd the whole popu can be wiped out by a single event ( disease )
ways genetic diversity is increased by
- mutation of the gene producing an allele, some can be advantagous
- when org from a popu migrate and reproduce into ano population introduces new allele of the gene - gene flow
genetic diversity allows natural selection to occur because some cha more ad than others
genetic bottleneck
when an event causes big reduction in a population
- reducing number of different alleles in the gene pool and reduces genetic diversity
- the survivors reproduce and larger the population created from a few individual.
founder effect
- when a few organisms from a population start a new colony
- there is only a small number of diifferent allele in the intial gene pool
- genetic diversity greatly reduced
natural selection
MSPF
- mutation - causes new allele to be formed , some can be benificial while others are disad
- org with ad allele survive and reproduce
- passing on the ad allele to the next generation
- the offspring also survive more due to ad allele reproducing and pass on the ad gene
- this slowly increases the frequency of the ad allele leading to evolution as ad allele is more common
adaptation
- features that helps an org to survive in there envi
- behavioural ( way org behave )= scorpions dance before mathing
- physiological (process inside org body)= bear hibernating - lower their rate of metabolism
- structure ( structural features of organism body’s ) = hump on cammel
directional selection
- when indi with alleles for cha of extreme type more likely to survive and reproduce
- could be response to change in envi
stabilising selection
when indi with allele for cha toward the middle range more likely to survive and reproduce
- occurs when evni not changing - reduces the range of possi characteristics
