variation Flashcards
(22 cards)
what does variation in height of species show
that individuals of the same species are similar but never exactly the same
2 types of variation
genetic and environmental
what causes genetic variation
the combination of genes from 2 parents
what causes environmental variation
the conditions (environment) that organisms live and grow in
what is continuous variation, example and what is the shape of it on a graph
when the individuals in a population vary within a range with no dintinct categories eg height
bell shaped curve
what factors influence characteristics to be continuous and discontinuous variation
continuous - more than 1 gene and influenced by both genetic and environmental factors
discontinuous - 1 gene and not influenced by environmental factors
what is discontinuous variation and example
when there’s two or more distinct categories and each individual only falls into one eg blood group
what causes genetically different offspring from parents
sexual reproduction as fertilisation provides a single cell with a new set of pairs of chromosomes
what is sexual reproduction
the fusion of male and female gametes
what causes offspring’s to be genetically identical / a clone to that parent
asexual reproduction as there’s only one parent which divides by mitosis
- no chromosomes are mixed and no variation
what is a mutation
a random change in an organisms DNA
how do new alleles arise
from mutations in existing alleles
do mutations occur at random
yes
what is mutation rate and how can chances of mutations be increased
The number of mutations that occur in a gene or organism overtime
greater exposure to ionising radiation = greater chance of mutation
can mutations effect organisms
most can’t but some can be beneficial or harmful
negative example of mutations
causing genetic disorders to be passed on in families such as inheritance of cystic fibrosis
what is cystic fibrosis
A genetic disorder caused by the mutation of a gene which results in the body producing lots of thick sticky mucus in the bronchioles and pancreas
is the allele that causese cystic fibrosis dominant or recessive
recessive
what are people with only one copy of the cystic fibrosis allele called and if both parents have one copy, what the chance of the child having the disorder
carriers
1/4
why is it difficult for gene therapy to treat cystic fibrosis
its difficult to gets these new alleles into the correct cells and working normally in the body
How is gene therapy delivered to the patient to treat their cystic fibrosis?
The genes can be introduced into the lung tissue via an inhaler
why is gene therapy not a cure for cystic genesis
as the treated cells are replaced by the body overtime
