Flashcards in 6.2 Patterns Of Inheritance & Variation Deck (32):
Why does variation arise?
Due to random mutations
Random mutations are essential for what to take place?
Variation within a species can arise from which factors?
Give examples of variation arising from both genetic and environmental factors?
Some plants suffer from chlorosis what does this affect?
A plants ability to photosynthesise
Don't produce enough chlorophyll
Plants look pale and yellow
Most plants have genes coding for chlorophyll so what causes chlorosis?
What 3 environmental factors can cause chlorosis?
Lack of light
How does chlorosis occur due to lack of light?
Plants turn off chlorophyll production to reserve resources
How does chlorosis occur due to mineral deficiency?
Lack of iron which is needed as a cofactor to the enzymes making chlorophyll
Lack of magnesium to make chlorophyll
How does chlorosis occur due to virus infections?
Interfere with metabolism of infected cells so they can no longer make chlorophyll
what is body mass mostly determined by?
environmental factors - diet
in some cases body mass is genetic, what happened to the obese mouse?
mutation in chromosome 8 caused it to deposit more fat
genetic variation is caused by what?
the alleles you inherit resulting in different characteristics being displayed
combination of alleles inherited are determined by what?
meiosis and random fusion of gametes at fertilisation
what are alleles?
different versions of genes
what is an organisms genotype?
the combination of alleles an organism inherits for a characteristic
what is an organisms phenotype?
an organisms physical observable characteristics
what is a dominant allele?
version of gene always expressed if present
what is a recessive allele?
version of a gene only expressed if two copies are present in an organism
what is homozygous?
two identical alleles for a characteristic
what is heterozygous?
two different alleles for a characteristic
what is continuous variation?
a characteristic that can take any value within a range
what is discontinuous variation?
a characteristic which can only appear is specific discreet categories
what factors cause continuous variation?
genetic and environmental
what factors cause discontinuous variation?
what is continuous variation controlled by?
polygenes - a number of genes
what is discontinuous variation controlled by?
one or two genes
give examples of continuous variation:
leaf surface area
length of parts of the body
give examples of discontinuous variation:
round and wrinkled pea shape
is discontinuous variation qualitative or quantitative?
is continuous variation qualitative or quantitative?