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Genetic Variation (Mutation (point (chromosomal) mutation (Substitution,…
Genetic Variation
Mutation
point (chromosomal) mutation
Substitution
Deletion
Insertion
Occurs at only one point on chromosome.
somatic mutation
can not be inherited
occurs in all body cells (apart from gametes)
gametic mutation
can be inherited
occurs in gametes
ova
from females
xx
produced in ovaries
sperm
from males
xy
determines if offspring are xx (female) or xy (male)
produced in testes
caused by mutagens
mutagens: chemicals, ultraviolet light, radiation
Block (gene) mutation
deletion
genes are removed from the original chromosome and lost
inversion
the genes are rearranged/inverted
rearranges the genetic information
translocation
relocation of genes from one chromosome to another
the new genes are not coded for
duplication
genes are copied and added on to the chromosome
extra genes are not coded for
Changes DNA transcription to messenger MRNA which translates to a protein.
Organisms such as bugs can become immune to pesticides
harmful
affects an organisms ability to survive
e.g. lack of tumour suppressing genes
causes cancer
beneficial
enhance an organisms ability to survive
e.g. resistance to pesticide
silent
do not have any visible affects to an organism
no change to the amino acids produced
substitution point mutation
variation
continuous
Height
weight
hand span
A complete range of measurements from one extreme to another.
discontinuous
Tongue rolling
Earlobe attachment
Bloodtype
Eye colour
Characteristics that fall into a number of distinct classes/categories.
helps a species to survive in changing environments
Differences within the same species.
Reproduction
Asexual
clones species/no variation
therefore the species cannot adapt to changes in environment
if the species cannot survive in changed environment they will become extinct
one parent
does not need to find a mate
Fast & efficient
i.e. aphid
sexual
two parents
an organism with sperm and an organism with ova
mate-selection
variation in a species
helps species to survive changes in environment
takes time
has to find a mate
i.e. humans
Environment
may alter the expression of genotype
Food and nutrient availability, competition, light intensity
Modification of expected phenotype.
Meiosis
Special type of cell division.
causes variation
Segregation
Homologous chromosomes split so each gamete receives one allele for each pair. Resulting in all daughter cells being unique.
four daughter cells are produced from parent cell
Fertilisation
Male gamete and female gamete join, forms Zygote
crossing over
Homologous chromosomes can swap part of chromosomes breaking gene combinations. Increasing variation between gametes.
point that chromatids cross over : chiasma
independent assortment
Homologous pairs of chromosomes randomly line up during Meiosis. This meaning random combination of alleles end up in a gamete
cell division that forms gametes
23 chromosomes each
Produces gametes.
Occurs in testes and ovaries