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population genetics (Genetic variation:
genetic variation =
a…
population genetics
Genetic variation:
genetic variation =
a difference in genotype
causing a difference in phenotype
- it comes about in
sexual reproduction,
(not in asexual reproduction
except form mutations)
Asexual reproduction:
- has only 1 parent
- offspring are identical to
the parent & to each other
- typically rapid &
produces many offspring
- only source of variation is from mutations
- becase no other variation to help the
population if conditions/environment change,
its less likely for survival of the species
sexual reproduction
- involves 2 parents
- offspring have 1/2 their genes from
1 parent and 1/2 their genes
from the other parent
- each parent makes their own
gamete /sex cell, by meiosis
causes variation in individuals in the population due to
- random chromosome assortment
- random fusion of gametes during fertilization
each gamete in unique, it is a one of a kind combination of alleles- so when a male and female gamete fuse they create a zygote/offspring that is unique, and this grows into a unique individual
Identical twins:
no human has exactly the same genetics, except identical twins, because they game from the same embryo that split in half
- develop from the same fertilized egg/zygote
- DNA s same, there are genetically identical
- same inherited traits bu different acquired traits
- if the zygote doesn't fully separate; this causes Siamese twins
variation:
mutation is the ultimate cause of variation.
- without mutations there wouldn't be different alleles
(A mutation is a change in the order of bases of DNA)
- because DNA carry the code for making a protein & therefor determining a trait, therefore mutations can cause a new phenotype/trait
- if the mutation causes a phenotype that provides a survival advantage, it will help the individual to survive, reproduce and pass on its genes, & it may become common in the population.
(mutations will only be passed on if they occure
in sex cells & that cell is then fertilized and servives)
sexual vs. asexual reproduction affecting variation:organisms that...
- reproduce sexual = show lots of variation
(form carrying out meiosis (+mitosis),
therefore 'all' offspring have unique l set of alleles)
- reproduce asexualy = no variation ( except form mutations)
(because they only do mitosis,
witch produces identical cells)
Population genetics
population genetics reveals relationships between species, and often provides clues to the origens of species
this genetic study proposes questions such as;
- what makes 1 certain group able to adapt better than others group in the same species
- what are the genetic differences and similarities among populations
- how has evolution, by means of natural selection given us changing populations and genetics within the population over time
-
study of a population (species) genetics as a whole, rather than the genetics of an individual organism
population genetics is the study of how genetics effects evolution and how the different genes effect species as a whole