genetic variation Flashcards
what is variation
differences between the individuals of the same species
what is genetic variation
all the different alleles in a species (gene pool)
what is a species
groups of organisms that can interbreed to produce fertile offspring
what could variation be a result of?
genetics or environmental
causes of variation?
mutations
crossing-over in prophase 1 of meiosis
independent assortment of chromosomes in anaphase 1 in meiosis
independent assortment of chromatids in anaphase 2 of meiosis
random fertilisation of gametes
environment
genetic causes of variation
mutations
crossing-over in prophase 1 of meiosis
independent assortment of chromosomes in anaphase 1 in meiosis
independent assortment of chromatids in anaphase 2 of meiosis
random fertilisation of gametes
causes of variation from sexual reproduction
crossing-over in prophase 1 of meiosis
independent assortment of chromosomes in anaphase 1 in meiosis
independent assortment of chromatids in anaphase 2 of meiosis
random fertilisation of gametes
what is the only source of new alleles?
mutations
what causes the shuffling of existing alleles into new combinations?
causes of variation excluding mutations
what is a mutation
a change in DNA base sequence
only source of new alleles
what causes mutations
caused naturally (by errors in DNA replication) or artificially (due to mutagens eg chemicals or radiation)
how to detect large-scale mutations?
can be detected by a karyotype (photo of chromosomes)
looking for differences in:
- chromosome number
- chromosome shape
- chromosome size
- chromosome banding pattern (using dyes)
how to detect small-scale mutations?
can be detected by sequencing the DNA eg substitution, deletions, addictions
what is continuous variation
the characteristic / trait occupies a range of values eg IQ, height
determined by many genes (polygenetic characteristics) with each gene having multiple alleles
more influenced by the environment
what is discrete / discontinuous variation
the characteristics / trait occupies falls into categories eg blood group
graph is drawn using bars
determined by one gene (monogenic characteristics), rarely two genes, such genes have two alleles (rarely three genes)
less influenced by the environment
